THYROID CANCER IN UKRAINE AFTER CHERNOBYL

M Tronko
T Bogdanova
V Saenko
GA Thomas
I Likhtarov
S Yamashita
Editors

THYROID CANCERIN UKRAINE AFTER CHERNOBYL

dosimetry, epidemiology,

pathology, molecular biology

M Tronko, T Bogdanova, V Saenko,
GA Thomas, I Likhtarov, S Yamashita
Editors

THYROID CANCERIN UKRAINE AFTER CHERNOBYL
dosimetry, epidemiology, pathology, molecular biology

2014ISBN 4-931481-08-6© 2014 M Tronko, T Bogdanova, V Saenko, I Likhtarov, GA Thomas, S Yamashita© 2014 Nagasaki Association for Hibakushas’ Medical Care (NASHIM)
All rights reserved
Printing and binding: IN-TEX, Nagasaki, Japan. Printed in Japan

Editors

Tronko Mykola, MD, PhD, Professor, Academician of NAMS – Director of
the Institute; Head, Department of Fundamental and Applied Problems ofEndocrinology, State Institution “VP Komisarenko Institute of Endocrinology
and Metabolism”, National Academy of Medical Sciences of Ukraine, Kyiv,
UkraineBogdanova Tetiana, PhD, Professor – Head, Laboratory of Morphology
of Endocrine System, State Institution “VP Komisarenko Institute of
Endocrinology and Metabolism”, National Academy of Medical Sciences of
Ukraine, Kyiv, Ukraine

Saenko Vladimir, PhD – Associate Professor, Department of Health Risk
Control, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki,
Japan

Thomas Geraldine, PhD – Professor of Molecular Pathology, Department ofSurgery and Cancer, Imperial College London, UK

Likhtarov Ilya, PhD, Professor – Head, Department of Dosimetry andRadiation Protection, State Institution “National Research Centre for
Radiation Medicine”, National Academy of Medical Sciences of Ukraine;
Director, Ukrainian Radiation Protection Institute, Kyiv, Ukraine
Yamashita Shunichi, MD, PhD – Trustee and Vice-President, Nagasaki
University; Professor and Chairman, Department of Radiation Medical
Sciences, and Department of Health Risk Control, Atomic Bomb Disease
Institute, Nagasaki University; Vice-President, Fukushima Medical University;
Appointed Professor and Vice-Director, Radiation Medical Science Center for
the Fukushima Health Management Survey, Fukushima, Japaniii

Contributors:

Chepurny Mykola – Scientist, Laboratory of Radiation Protection, State
Institution “National Research Centre for Radiation Medicine”, National
Academy of Medical Sciences of Ukraine; Ukrainian Radiation protection
Institute, Kyiv, Ukraine

Gerasymenko Valentina – Junior Scientist, Laboratory of Radiation
Protection, State Institution “National Research Centre for Radiation
Medicine”, National Academy of Medical Sciences of Ukraine; Ukrainian
Radiation protection Institute, Kyiv, Ukraine

Ivanova Olga – Scientist, Laboratory of Radiation Protection, State
Institution “National Research Centre for Radiation Medicine”, National
Academy of Medical Sciences of Ukraine; Ukrainian Radiation protection
Institute, Kyiv, Ukraine

Ito Masahiro, MD, PhD – Director, Department of Pathology, ClinicalResearch Center, National Nagasaki Medical Center, Nagasaki, Japan

Kashcheev Valerii, PhD – Senior Scientist, Federal State Institution «Medical
Radiological Research Center» of the Russian Ministry of Health, Obninsk,
Russian Federation

Kovgan Leonila, PhD, Doctor of technical sciences – Head, Laboratoryof Radiation Protection, State Institution “National Research Centre for
Radiation Medicine”, National Academy of Medical Sciences of Ukraine;
Ukrainian Radiation protection Institute, Kyiv, Ukraineiv

Contributors

LiVolsi Virginia, MD – Professor of Pathology and Laboratory Medicine;
Director, Strategic Initiatives and Quality Improvement, Anatomic
Pathology; Professor of Surgical Pathology in Surgery; Professor of
Otorhinolaryngology Head and Neck Surgery, University of Pennsylvania
Perelman School of Medicine, Philadelphia, PA, USA

Masiuk Sergiy, PhD – Senior Scientist, Laboratory of Radiation Protection,
State Institution “National Research Centre for Radiation Medicine”, National
Academy of Medical Sciences of Ukraine; Ukrainian Radiation protection
Institute, Kyiv, Ukraine

Mine Mariko, PhD – Professor, Research Center for Nuclear WeaponsAbolition, Nagasaki University, Nagasaki, Japan

Nakashima Masahiro, MD, PhD – Professor and Chairman, Department ofTumor and Diagnostic Pathology, Atomic Bomb Disease Institute, Nagasaki
University, Nagasaki, Japan

Schoetz Ulrike, PhD – Research Associate, Department of Surgery andCancer, Imperial College London, UK

Shpak Victor – Senior Scientist, Department of Medical Consequences of
the Chernobyl accident and International Cooperation, State Institution“VP Komisarenko Institute of Endocrinology and Metabolism”, National
Academy of Medical Sciences of Ukraine, Kyiv, Ukrainev

Contributors

Williams Dillwyn, MD, FMedSci, Emeritus Professor of Histopathology –Honorary Senior Visiting Fellow, Department of Public Health, University ofCambridge, Cambridge, UK

Zurnadzhy Liudmyla, MD, PhD – Senior Scientist and part-time pathologistof highest category, Laboratory of Morphology of Endocrine System, State
Institution “VP Komisarenko Institute of Endocrinology and Metabolism”,
National Academy of Medical Sciences of Ukraine, Kyiv, Ukrainevi

Acknowledgements

The authors gratefully acknowledge financial support provided by
the following bodies since 1994: The European Commission (Grant
numbers ECP8, ERB15CT97 1100, FIR1200120123, FP7 211712), theNational Cancer Institute of the USA (grant number 5U24CA082102),
the Sasakawa Memorial Health Foundation of Japan and the World
Health Organisation. We acknowledge the commitment of ourcolleagues at the Institute of Endocrinology and Metabolism (IEM) in
Ukraine, especially the staff of the laboratories of Morphology and of
Radiation Damage of Endocrine System who collected pathologicalmaterial and frozen samples, extracted DNA and RNA for different
scientific studies, and of Surgery Department who operated on mostpatients with thyroid tumors included in the present analysis. We
thank Pathology Panel of the Chernobyl Tissue Bank (CTB): Professors
D Williams (UK), V Livolsi (USA), J Rosai (USA), M Ito (Japan), J Hunt (USA),G Fadda (Italy), A Abrosimov (Russian Federation), and T Bogdanova(Ukraine) for consensus pathological diagnoses of the CTB cases.
Support of our colleagues, members of panels overseeing the CTB
in the past and at present, is also gratefully acknowledged, as is thegenerosity of patients who have donated their tissue specimens to
the CTB.
We would also like to thank Nagasaki Association for Hibakushas’
Medical Care (NASHIM) for financial support of this publication
and all our colleagues from Belarus, Russia and different countriesof Europe, USA and Japan who worked with us and/or performed
research projects on thyroid cancer after Chernobyl. Our personalacknowledgements to A Statsenko (IEM, Ukraine), T Rogounovitch,
A Bychkov, J Takahashi, and Y Kawaguchi (Nagasaki University, Japan)
for their essential assistance in manuscript preparation.

vii

Preface
The population living in areas exposed to radioiodine in fallout from the Chernobyl
accident has shown a significant rise in thyroid cancer, particularly in those who werechildren and adolescents at the time of the accident. This rise in thyroid cancer is the
only scientifically proven effect of the accident on health of the local population. The
temporal and geographic distribution of thyroid cancer cases diagnosed in young
patients is suggestive of a common causative event, i.e. internal exposure of the
thyroid gland to radioiodine. Thyroid dose per unit intake of iodine isotope is higher
for children then for adults mostly due to the smaller size of the thyroid in children. The
background rate of childhood thyroid cancer is very low in unexposed populations;the additional thyroid cancer incidence in young patients is therefore particularly
striking.
The VP Komisarenko Institute of Endocrinology and Metabolism of the National
Academy of Medical Sciences of Ukraine was a leading research center for study
and treatment of thyroid diseases in Ukraine, and took a principal role in treatingthese patients as soon as the rise in cases became apparent. A specialized Clinicalmorphological Registry of thyroid cancer of subjects at high risk was establishedin the Institute in 1992 and is still maintained today. The Histological archive
stores pathological material from cases, most of which have been reviewed by theinternational experts since 1994.
The Ukrainian cases account for over 60% of the international Chernobyl Tissue Bank
(CTB). For more than 70% of them matched pairs of samples from tumor and normal
tissue are available. These are widely used by the leading research centers in the world
to study various aspects of thyroid carcinogenesis. Recent efforts to supplement the
CTB database with calculated individual thyroid exposure dose estimates have made it
possible to search for markers of thyroid cancer with a radiation etiology.
Investigations performed on the same pathologically verified samples allow thecomparison of the results from different projects as well as an in-depth integrative
analysis.
The international team of authors of this book attempts to provide an overview
of the large number of unique materials obtained from studies of Ukrainian thyroid
cancer that have been accumulated over the years after the Chernobyl accident.
Comprehensive scientific analysis is now expected to be useful for future studies ofradiation-associated thyroid cancers.
The Editors:

Mykola Tronko
Tetiana Bogdanova
Vladimir Saenko
Ilya Likhtarov
Geraldine Thomas
Shunichi Yamashitavii

Contents
Editors ............................................................................................................................................................. iii
Contributors ................................................................................................................................................. iv
Acknowledgements..................................................................................................................................vii
Preface
Editors: M Tronko, T Bogdanova, V Saenko, GA Thomas, I Likhtarov, S Yamashita ..................viii
Chapter 1
Overview of the Chernobyl accident and its consequences
V Saenko, T Bogdanova, M Tronko, S Yamashita .................................................................................. 1
Chapter 2
Different levels of thyroid dose individualizationof the Ukrainian donors in Chernobyl tissue bank
I Likhtarov,, L Kovgan, S Masiuk,, M Chepurny, O Ivanova, V Gerasymenko, M Tronko,
T Bogdanova, GA Thomas ..........................................................................................................................19
Chapter 3
Epidemiology of thyroid cancer in Ukraine after Chernobyl
M Tronko, V Shpak, T Bogdanova, V Saenko, S Yamashita ................................................................39
Chapter 4
Thyroid cancer pathology in Ukraine after Chernobyl
T Bogdanova, L Zurnadzhy, VA LiVolsi, ED Williams, M Ito, M Nakashima, GA Thomas ..........65
Chapter 5
Comparative pathological analysis of papillary thyroid carcinoma
in age-matched groups of patients born before and after Chernobyl
T Bogdanova, V Saenko, L Zurnadzhy, I Likhtarov, L Kovgan, S Masiuk, V Kashcheev,
VA LiVolsi, ED Williams, M Ito, M Mine, GA Thomas, M Tronko, S Yamashita ........................... 109
Chapter 6
Ukrainian contribution to the international Chernobyl Tissue Bank (CTB) project
GA Thomas, T Bogdanova, M Tronko, S Yamashita ......................................................................... 135
Chapter 7
Molecular biology studies of Ukrainian thyroid cancer after Chernobyl
U Schoetz, V Saenko, S Yamashita, GA Thomas ................................................................................ 143
Conclusion
The Authors ................................................................................................................................................. 175

vii

Overview of the Chernobyl accident and its consequences

Chapter1

V Saenko, T Bogdanova, M Tronko,
S Yamashita

Overview of the Chernobyl accident
and its consequences

The accident at Chernobyl nuclear power station was the worst technogenic catastropheof the last century that involved radiation. Massive releases of radioactive substances led
to radioactive contamination of territories surrounding the accident site through fallouts.
Before Chernobyl, the only experience of massive radiation exposure known to humankind
was the A-bombings of Hiroshima and Nagasaki in 1945. The character of radiation exposureof population after Chernobyl was principally different from that in Japan: protracted versus
acute single dose, mostly internal versus external irradiation, influence of the different
spectra of isotopes, irregular and patchy radioactive contamination of the environment,
radiation exposure of millions of all ages. That is why many consequences related to health,radioecology and society could not be anticipated or reliably estimated quickly.
In this chapter we overview some technical aspects of the accident and information onradioactive releases that caused contamination of territories in the former Soviet Union
countries – Ukraine, Belarus and Russia. We also describe the major groups of population
affected by the accident and consider their dosimetric information. Epidemiological andmedical studies from the early stages of the accident until present and their most salient
results will be described. Finally, the comparative epidemiological information on thyroid
cancer, one of the major health consequences of the accident, particularly focusing on theresident of contaminated territories will be given to compare the three affected countries.
Note that the detailed epidemiological analysis of thyroid cancer in Ukraine after Chernobyl
is presented in Chapter 3 of this book.
The accident at Reactor Number 4 of the Chernobyl Nuclear Power Plant (CNPP) located at
the north of Ukraine close to the junction of the borders of the three states, Ukraine, Belarus
and Russia, took place shortly after midnight on April 26, 1986. According to UNSCEAR [1],the course of events could be briefly summarized as follows. Due to some reactor design
drawbacks and human errors during experimental operations immediately preceding theaccident, irregular fuel overheating and fragmentation in the active zone led to the rapidtransfer of excessive heat to the coolant water and induced the shock wave breaking the
primary coolant system pipeline joints. Leaked water instantaneously turned to steam;this first explosion caused the reactor core displacement during which the remaining
cooling water flew out of the system. Without coolant, part of the fuel vaporized becauseof overheating, eventually resulting in a large explosion that destroyed the reactor and1

Chapter 1

the building, and dispersed reactor debris and radioactive materials to CNPP, plant vicinity
and into the environment. The initial fires that occurred after the major explosion were put
under control by the end of the night of the accident. However, fuel materials remaining atmeltdown site grew hot, ignited combustible products formed in the disrupted core milieu
and caused an explosion-like fire. Tremendous efforts have been made to extinguish thisfire, including dumping of various fission- and fire-control materials from helicopters, but
the radioactive releases continued for approximately 10 more days [2,3].
There were 7 deaths during the first night of the accident: two staff members and fivefiremen in fire fighting actions. Among 237 firemen and CNPP employees examined withinseveral next days for acute radiation sickness, manifestations of such of varying degrees ofseverity were found in 134 individuals. Despite the intensive therapy, including 13 bonemarrow transplantations, 28 patients died within 4 months after the accident for various
causes of death among which myelosuppression was the major reason. Nineteen moredeaths were registered until 2004; in these cases bone marrow failure was unlikely theunderlying cause [4].
According to the estimates, the release of radioactivity from the destroyed reactor
totaled to about 13 EBq (1EBq=1018 Bq) [1,5,6]. The main radionuclides are listed inTable 1.1 of which 131І and 137Cs are radiologically most significant.
Radioactive emissions from CNPP were characterized by a wide spectrum ofphysicochemical forms and composition: gaseous, steam aerosol, aerosol mixtures, fuelparticles, mineral particles with entrapped radionuclides, aggregates of different mineralparticles, and organic compounds. The composition varied from monoelement noble
gases and atomic iodine or ruthenium, to multi-element compounds and aggregates, fuelcomponents, graphite, silicates and others, each with different radionuclide proportions [5].
Over 90% of 90Sr, 141,144Ce, and isotopes of Pu and 241Am were released in the form of fuelparticles measuring 10 μM and less [5]. 75% of 137Сs contamination within the exclusionzone (the 30-km zone around CNPP) could be attributed to this physical form. At longer
distances, contamination of the territories in European countries was due to steam-aerosoland gaseous mixtures, and to the particles of submicron size, containing 103,106Ru, 131,133I,
132
Te, 134,137Cs and radioactive noble gases. The same isotopes were also detected in Pacificand Atlantic Oceans, and even in fallouts in Americas and Asia thus displaying the global
scale of the accident. After a protective sarcophagus (object «Shelter») was upbuilt aroundthe destroyed reactor and the building in November 1986, active emissions into theenvironment were not practically observed [1,2].
The dynamic meteorological conditions, including the wind, cloudiness, temperature,humidity, precipitations and their intensity in combination with varying physicochemical
characteristics of radioactive materials released at different times after the reactor
destruction defined the inhomogeneous pattern of the ground contamination [7,8,9].
Figure 1.1 demonstrates reconstructed plume traces over the part of Europe.
Further monitoring of the territories allowed establishing contamination patternbased on average 137Cs deposition densities (this isotope is easy to measure, has a long
half-life and is radiologically significant) as shown in Figure 1.2 for the territories around
Chernobyl. The highest density of contamination is observed in CNPP vicinity; however thelevels exceeding expected background could be detected as far as up to 3000 km from theaccident site.
2

Overview of the Chernobyl accident and its consequences

Table 1.1
Principal radionuclides released due to the Chernobyl accident*
Radionuclide
Half life
Noble gases
85
Kr
10.72 y133
Xe
5.25 dVolatile elements
129m
Te
33.6 d132
Te3.26 d131
I8.04 d133
I20.8 h134
Cs
2.06 y136
Cs
13.1 d137
Cs
30.0 yElements with intermediate volatility
89
Sr50.5 d90
Sr
29.12 y103
Ru39.3 d
106
Ru
368 d
140
Ba
12.7 dRefractory elements (including fuel particles)95
Zr
64.0 d99
Mo2.75 d141
Ce32.5 d
144
Ce
284 d
239
Np
2.35 d238
Pu
87.74 y239
Pu
24,065 y240
Pu
6,537 y241
Pu
14.4 y242
Pu
376,000 y
242
Cm
18.1 yActivity released, PBq
33~6,500240~1,150~1,760~2,500
~47
36
~85
~115
~10
>168
>73
240
84
> 72
84
~ 50
400
0.015
0.013
0.018
~2.6
0.00004~0.4* Decay corrected to 26 April 1986
Data are inferred from refs. [2,8,17,20]

Territories of Belarus, Ukraine and Russia were affected by the accident most heavily,
as specified in Table 1.2. From the total 137Cs activity of about 64 TBq (1.7 MCi) depositedin Europe in 1986, Belarus received 23%, Russia - 30% and Ukraine - 18% resulting inradioactive contamination of approximately 3% of the European part of the former Soviet
Union [10]. There were also contaminated areas in Austria, Finland, Germany, Norway,
Romania and Sweden.
3Chapter 1

Table 1.2
European countries contaminated by Chernobyl fallouts in 1986*
Area with 137Cs deposition density range (per km2)
37-185 kBq/m2

185-555 kBq/m2 555-1480 kBq/m2 > 1480 kBq/m2

Russian Federation

49800

5 700

2100

300

Belarus

29900

10200

4 200

2200

Ukraine37 200

3200

900

600

Sweden

12000

-

-

-

Finland

11500

-

-

-

Austria

8600

-

-

-

Norway

5200

-

-

-

Bulgaria

4800

-

-

-

Switzerland

1300

-

-

-

Greece

1200

-

-

-

Slovenia

300

-

-

-

Italy

300

-

-

-

Republic of Moldova

60

-

-

-

* Based on refs. [1,9]An important role in radioactive contamination of the environment was played byradioactive 131,132,133,135I isotopes, which are short-lived radionuclides belonging to thegroup of light volatile substances. It is worth mentioning, however, that only 131І has a highradiological significance. Among other isotopes, only 133,135І could increase the general
exposure dose, especially for the thyroid, but due to their short half-lives their effect isrestricted to the areas within the near zone around CNPP.
Because of the rapid decay of 131I, collection of a large number of samples for detailed
analysis was difficult [11]. However, the results of model calculations based on the limited
number of measurements and determinations of 131I/different radionuclides ratios,
especially 137Cs (which varied 5-60-fold in different measurements), allowed reconstructionof contamination density maps [1,5,12]. The most contaminated in Ukraine, are 6 northernand central regions: Cherkasy, Chernihiv, Kyiv, Rivne and Zhytomyr regions, and Kiev-city(Fig. 1.3). In Belarus, the 3 regions in the east and south-east: Brest, Gomel and Mogilev;
and in Russia 4 south-western regions: Bryansk, Kaluga, Tula and Orel. The refined 131I
contamination data were considered by UNSCEAR and enabled calculation of thyroid dose
estimates [13]. This is essential for radiation epidemiology and public health assessment ofhealth consequences of the accident.
Most radionuclides released by the accident have already decayed. Attention over the
next few decades will likely to be paid to 137Cs and 90Sr; the latter remains more importantin the areas close to CNPP [5].
4Overview of the Chernobyl accident and its consequences

Figure 1.1. Calculated plume formation according to meteorological conditions for radioactive
releases on corresponding dates just after the Chernobyl accident [7].

Figure 1.2. Ground deposition of 137Cs in Ukraine, Belarus, and Russia around the accident site [1].

5Chapter 1

Figure 1.3. Cumulative 131I surface ground deposition in Ukraine (kBq/ m2) due to the Chernobyl
accident [12].

There are three major categories of individuals considered for estimation of radiation
health effects after Chernobyl. These are the workers involved in the actions during theaccident or in the aftermath mitigation, evacuated persons and residents of contaminatedterritories. They all were exposed to radiation at different time after the accident, under
different circumstances and to different spectra and amounts of radioactive elements.
Thus, accumulated effective doses are quite different between the groups and furthermore
there are large uncertainties in dose estimates.
The first category is further subdivided into those who were at CNPP during the firstday of the accident and took part in emergency measures, and those who were engaged
into recovery operations from 1986 to 1990. In the literature these workers are often andcollectively referred to as “liquidators”, the term officially introduced in the former Soviet
Union. There were about 600 emergency workers at CNPP during May 26, and about 600,000
of liquidators including both civilians and servicemen until 1990. Estimated external doses
in 134 emergency workers with acute radiation sickness manifestations ranged 0.8-16 Gy
being noticeably higher than internal doses calculated to be between 0.021 and 4.1 Gy
for the thyroid in 23 firemen who died of bone marrow failure [14]; it was suggested thatthe lower thyroid doses might have been due to stable iodine pills taken by emergency
workers. Among liquidators, the average effective doses ranged from 15 mSv to 170 mSv
with individual variations from <10 mSv to >500 mSv in 1986-87 [1]. Internal exposures to6Overview of the Chernobyl accident and its consequences

the thyroid might have ranged from <0.15 Gy to 3 Gy with an average of 0.21 Gy in those
who took part in the activities in and around CNPP during the first few months after theaccident [15] as short-lived radioiodine isotopes largely decayed after that.
There has been also the massive evacuation of residents of the nearest settlements
depending on radiological situation and the distance from CNPP [16-19]. On April 27, about
50,000 persons were evacuated from the town of Pripyat located 3 km from CNPP, wheremost employees and their families resided before the accident. During 10 days after theaccident, through May 7, 1986, a similar number of persons who lived inside the 30-km zone
surrounding CNPP were evacuated in Ukraine and Belarus. Active evacuations continued
until September, 1986 and totaled in about of 116,000 relocation, mostly from Ukraine andBelarus. Estimates of external effective doses reconstructed for about 30,000 residents of the
30-km zone indicate the range from 0.1 mSv to 380 mSv with an average of 17 mSv [20].
Mean thyroid doses from 131I, based on about 5,000 direct measurements and about 10,000
questionnaires collected from Ukrainian evacuees were 0.11-3.9 Gy in children, 0.066-0.39
Gy in adolescents and 0.066-0.40 Gy in adults [21,22]. In Belarussian evacuees the estimatesare 1-4.3 Gy, 1 Gy and 0.68 Gy, respectively [23]. Concordantly, these investigations havedemonstrated an inverse correlation between thyroid dose and age at exposure.
With regard to the residents of contaminated territories, reconstructed maps of soil
contamination with 137Cs (Figure 1.2) taken together with demographic data for Belarus,
Russia and Ukraine indicate that population of contaminated territories (i.e. with 137Cs levels
exceeding 37 kBq/m2) was above 5 million at the time of accident, with about 1 million ofchildren (<15 years old) and approximately 200,000 adolescents. Since the number of residentsof contaminated territories is substantially greater than in the two categories of exposed
persons described above, and also because the residents include individuals of all ages
who might have been exposed to diverse radiological conditions at different geographicallocations, dose estimates in them are more complicated and are intrinsically associatedwith uncertainties particularly seen in the differences between averaged collective andindividual doses. Models of accumulated dose from external sources are based on soil 137Cs
contamination levels and are normalized to isotope deposition density. Estimates of external
doses range from 11 μSv/kBq/m2 to 24 μSv/kBq/m2 in 1986 for contaminated territories of thethree countries being higher in rural and lower in urban areas [1]. Study of external doses in
one contaminated settlement in Russia in 1987 found individual external doses to be within
2-13 mGy range with a mean of 5 mGy [24]. Internal doses for the thyroid rely on direct thyroid
measurements (several hundred thousand have been taken cumulatively after the accident),
individual questionnaires and computer modeling. Estimates indicate that the doses varied
in a wide range from <0.05 mGy to >2 Gy in Belarussian, Russian and Ukrainian individualsof all age groups with averages of <0.3-0.7 Gy in children and individual doses up to 10 Gy[25-31]. Thyroid doses exceeding 2 Gy were observed almost exclusively in younger children
aged less than 4 years [31] and they usually were higher in the residents of rural than in urban
areas with similar contamination level [30]. More detailed information on thyroid dosimetry
is presented in Chapter 2 of this book.
Organized administration of prophylactic or thyroid-blocking doses of stable iodine
was not common. According to some surveys, from1% to about 25% of the residents ofcontaminated territories reported taking KI pills shortly after the accident but the recall rate
was low [30,32]. In part this was due to poor preparedness to large-scale accidents such as
7

Chapter 1

one that happened at CNPP, and in part to inappropriate information from the authorities.
An official announcement in mass media appeared only two days after the reactor wasdestroyed on April 28. The delay was caused initially by the insufficient understanding of
the accident scale as well as apprehension of possible massive panic. It might be expectedthat if clear instructions on essential safety measures have been delivered swiftly and timely(e.g. taking KI pills, not consuming fresh milk and vegetables grown in the open plots,
not going outside, etc.), health consequences, at least for the residents of contaminatedterritories, would be less dramatic. Cost-benefit analysis performed in Belarus for 2,566
thyroid cancers in children and adolescents diagnosed and treated during 1990-2005
showed that if potassium iodide prophylaxis had been done, budget expenditures would
have decreased for $400,000 per 100,000 of population [33].
The scale of the accident and the number of people affected by it were unprecedented;
therefore initially it was very difficult to predict possible health consequences. In 2002,
S.Nagataki, evaluating state of knowledge about Chernobyl, designated the major postaccident periods as follows: 1986-1989 information difficult to obtain; 1990-1991 exchanges
with other countries initiated; 1992 case report: childhood thyroid cancer; 1992-1994 periodof ascertainment; 1995 ascertainment and search for causes; 1996-present investigations
carried out to the future [34].
First health screenings in the most contaminated areas around Chernobyl were started
shortly after the accident, mostly through local medical authorities. Only from 1990, after
the request from the Government of the former Soviet Union in October 1989, international
efforts were initiated to last until nowadays.
The first important collaboration was the International Chernobyl Project coordinatedby IAEA. During 1990-91, the 200 experts from 25 countries examined health stateincluding hematological, cardiovascular and thyroid disease, radiogenic cataract, cancer
prevalence, fetal abnormalities and mental health for possible radiological consequences
in a total of 825,000 people of 2,225 settlements in the three affected states [35]. One ofthe purposes was also to evaluate undertaken measures and to develop health-related
advices for population residing in contaminated areas. The major findings of this projectgenerally confirmed previously established surface contamination levels; the whole body
lifetime doses were estimated not to exceed 160 mSv being several times lower than initial
estimates of about 350 mSv; actual thyroid doses were difficult to confirm; stress andanxiety in the population were significant but apparently not radiation-related; no increasein leukemia or solid cancers was observed at that time; thyroid dose estimates in children
were suggestive of the possible increase in thyroid cancer incidence in the future; extent
of population evacuation and foodstuff restrictions appeared to be sometimes excessive.
In February 1990, the Government of the former Soviet Union appealed to Sasakawa
Memorial Health Foundation (SMHF) of Japan to provide assistance specifically to the
population of contaminated territories. SMHF in collaboration with the Japan Shipbuilding
Industry Foundation (at present the Nippon Foundation) created a 5-year program at first
entitled the “Chernobyl Sasakawa Health and Medical Cooperation Project”. According
to the report of experts who evaluated situation in Chernobyl areas, the major concerns
were fear and anxiety among the residents, poor informational support, and insufficientknowledge of health problems in the population. Therefore, the direct health examination,
8

Overview of the Chernobyl accident and its consequences

particularly in children, was identified as the highest priority task [36]. In May 1991, healthcheckups of children began in five health examination centers established in Kiev andZhytomir (Ukraine), Gomel and Mogilev (Belarus), and Bryansk (Russia) with a special focus
on direct thyroid dose measurement, thyroid examination and blood tests (also including
hormone and antibody measurements) according to the unified protocol. To implement
the project, SMHF donated to each center five mobile units equipped with whole bodycounters, ultrasound machines and blood analyzers, 10 buses for patients’ transportation
as well as other medical and diagnostic equipment, computers, supplies and medicines.
Until April 1996, 158,995 children aged 0-10 years at accident were examined. The project
also supported training in Japan and on-site, expert visiting of the five centers, andeducational materials and lectures for the residents. Among 120,605 analyzed patients,
585 (4.85%, range 1.01-17.69%) patients with thyroid nodules and 63 (0.52%, range 0.221.92%) with thyroid cancer were found with the highest rate among the residents ofthe most heavily contaminated Gomel region in Belarus aged 0-3 years at accident [37].
The prevalence of goiter was 18-54% but no correlation with whole body 137Cs count or
the level of 137Cs contamination at the settlement of residence was observed [38]. The
frequencies of hematopoietic malignancies, abnormal hematological parameters andthyroid autoimmunity also did not correlate with whole body 137Cs count or the level of137
Cs contamination [39]. The results of the project, which was the most reliable study at thetime, indicated a link between thyroid cancer in children and the Chernobyl accident andpointed at the need in further investigations.
In view of a high importance of the results obtained in 1991-1996, SMHF has extended the
project for 5 more years focusing on Gomel region of Belarus. A comparative study of thyroid
diseases in children born before and after the accident was designed to involve 21,601
persons examined from February 1998 to December 2000 using the approaches establishedduring the first project [40]. A total of 32 (0.15% of examined children) thyroid cancers werediagnosed of which 31 was in the group of 9,720 children born before the accident, one in achild born during April 27 - December 31,1986 (i.e., possibly exposed in utero) while no thyroid
cancers were detected in the group of 9,472 children born after the accident. The estimatedodds ratios of the frequency of thyroid cancer in the group born before the accident andin utero exposed group were 121 and 11, respectively, as compared to those born after theaccident. A conclusion about the likelihood of causal link between direct external or internal
exposure to short-lived radionuclides including 131I and 133I was drawn.
The extended SMHF project provided a good opportunity for collaboration with the
Belarus/Russia/EU/IARC epidemiological case-control study aimed at the evaluation of therisk of thyroid cancer after exposure to 131I and elucidation of risk-modifying factors. In a
united effort, which initially included all individuals with thyroid cancer aged less than 15
years at the time of accident from Gomel and Mogilev regions of Belarus and from Bryansk,
Kaluga, Tula and Orel regions of Russia (a total of 276 at the end of study) and at least
four closely matched population-based controls (1,300 persons) were analyzed. Individual
thyroid doses were reconstructed and used to estimate dose-response relationship. It
was found to be significant and linear up to 1.5-2 Gy [41]. Odds ratio for thyroid cancer
varied from 5.5 to 8.4 for a dose of 1 Gy according to different risk models being generallycomparable with risk estimates for external exposures [42]. Importantly, a strong modifying
9

Chapter 1

effect of iodine deficiency was observed: relative risk for developing cancer was 3.2 in iodine
deficient areas whereas a dietary supplementation with KI reduced the risk approximately
3-fold (relative risk of 0.34). This study was the largest population-based investigation inyoung people living in Chernobyl areas; it provided a strong definitive evidence of causal
association between the risk for thyroid cancer and internal exposure to radioiodine atyoung age. The major route of 131I ingestion by residents was its incorporation into foodchains of pastured cattle, mostly cows, and consumption of fresh milk as well as fromvegetables and fruits grown in open soil. Incorporation of 137Cs may have contributed todose formation. That is why both 131I in the thyroid and in milk, and 137Cs in soil, food and in
the body are considered for dose reconstruction [43].
The World Health Organization (WHO) has been playing an active role in studying
and managing health consequences of Chernobyl. One of the largest projects was theInternational Project on the Health Effects of the Chernobyl Accident (IPHECA) launchedin May 1991 and completed in 1996 with international budget support primarily fromthe Government of Japan and with the contribution from Czech Republic, Slovakia,
Switzerland and Finland [44]. IPHECA included a number of pilot projects: Brain damage
in utero, Epidemiological Registry, Hematology, Medical and psychological rehabilitationof Chernobyl liquidators, Oral Health, Radiation Dose Reconstruction, and Thyroid. In
collaboration with SMHF project, over 210,000 children were examined. The findings werein line with the earlier SMHF projects: by the end of 1994, 565 children (208 in Ukraine,
333 in Belarus and 24 in the Russian Federation) who lived in contaminated regions werediagnosed for thyroid cancer but no significant increase in the incidence of leukemia orother blood disorders were registered [45].
In February 1999, the WHO and SMHF started the Chernobyl Telemedicine Project
whose aim was to improve early diagnosis, treatment, and follow-up of patients withthyroid cancer, primarily in Gomel region of Belarus. A satellite-based telematic system
was established that allowed an exchange of thyroid ultrasound and cytology images,
and of related information on the patients between Thyroid Oncology Center in Minsk,
the Research Center for Radiation Medicine in Gomel and Nagasaki University School of
Medicine with synchronized databases [46-49]. By September 2000, information on 330
cases was entered into the database and reviewed independently thus improving diagnosis.
Another important project was the establishment of the Chernobyl Tissue Bank (CTB)in October 1998 based on funding from the European Commission, WHO, SMHF and the
U.S. National Cancer Institutes and approved by the Governments of Belarus, Russian andUkraine [50]. CTB activities and projects are described in Chapter 6 of this book.
Even at present, when major causes of health consequences of the CNPP accident, atleast with regard to thyroid cancer, are clarified, international activities continue. One ofthem is the Chornobyl Thyroid Diseases Study Group of Belarus, Ukraine, and the USA[51]. The study follows-up a cohort of 25,161 individuals (11,918 in Belarus and 13,243 in
Ukraine) born between April 26, 1968 and April 26, 1986, with direct thyroid measurements
available shortly after the accident to improve individual dose estimates and to collect
health-related information based on bi-annual (or annual) screenings. The project wasstarted in December 1996 in Belarus and in April 1998 in Ukraine.

10Overview of the Chernobyl accident and its consequences

During the first screening in 1998-2000, 45 thyroid cancers were detected in Ukraine[52]. An approximately linear dose-response relationship was found with excess relativerisk estimate of 5.25 per 1 Gy. The older age tended to associate with the decreased risk ofthyroid cancer. A fraction of cancers attributed to radiation was estimated to be 75% (95%
CI 50-93%).
Reconstruction of thyroid doses in Belarus is now ongoing for the newly evaluationof the risk of radiation-associated thyroid cancer [53]. In Ukraine, there are extensive risk
analyses of thyroid cancer and of other thyroid diseases among individuals exposed inutero to 131I from Chernobyl fallout [54] as well as of that of non-cancer thyroid neoplasms[55] and autoimmune thyroiditis [56]. The results of this large-scale project are expected tofurther refine conclusions of the earlier, concurrent and ongoing studies.
Clean-up workers is a group exposed to radiation at the accident site. Their thyroid
doses are mostly attributed to external exposures although those who took part in
mitigation efforts during the first two months might have received internal doses frominhaled radioiodines.
In 1997, based on a survey of 167,862 liquidators registered in Russian National Medical
Dosimetric Registry, 47 verified thyroid cancers were reported. An excess relative risk (ERR)of thyroid cancer of 5.31 per 1 Gy and an excess absolute risk of 1.15 per 104 person-years/
Gy were found [57]. By the end of 1998 a total of 58 thyroid cancers were diagnosed in a
subset of 99,024 liquidators from 6 regions of Russia [58]. A statistically significant increaseof standardized incidence rate (SIR) of thyroid cancer of 4.33 was found in this group ascompared to the background rate in male population of Russia. However, dose-response
relationship could not be established with ERR of -2.23 per 1 Gy (95% CI, -4.67; 0.22).
In Belarus, based on the information from National Cancer Registry, for about 120,000
liquidators in the country the standardized index of incidence for the period from 1993 to2000 was reported to be 24.4 per 100,000 while in the adult population of the country aged
more 30 years this index in 2000 was 5.67 [59].
Together these data indicate that thyroid cancer incidence is elevated in liquidators but
radiation risk needs to be further clarified through continuous observations.
In exposed residents of all ages, which also include evacuated persons, an increased
radiation-related risk was found in a number of epidemiological studies, as pointed
above, for those who were exposed to radioiodines during very young ages. Descriptive
epidemiology data on current situation with regard to thyroid cancer for the three countries
is summarized below.
In Ukraine, as shown in a recent analysis of a sample set approaching in size to thewhole population of the country, in 1989-2008 age-adjusted thyroid cancer incidence
rate in female residents of highly exposed regions increased from 3.34 to 10.99 (3.3-fold),and from 2.51 to 5.69 (2.3-fold) in low-exposure regions per 100,000 individuals [60].
In males, age-adjusted incidence rate grew from 0.87 to 2.64 (3.0-fold) and 1.37 (1.6-fold) inhighly exposed and low-exposure regions, respectively. For the patients diagnosed duringchildhood and adolescence, the analysis adjusted for screening and technological effects
shows that incidence rate was significantly elevated in the residents of highly contaminatedregions born before the accident as compared to those born after the accident while nosimilar difference was found for low-exposure regions. The average annual increase in11

Chapter 1

incidence was also significantly higher in the highly-exposed regions in all age subgroups
in both males and females suggestive of the radiation excess of thyroid cancers not onlyin children and adolescents but also in adults. Interestingly, in 2006 mean incidence ratio
in highly-exposed and low- exposure regions decreased in all female age subgroups andmost male subgroups, which may imply that the peak of radiation excess of thyroid cancer
in the country has been passed. These observations are important and need further doseresponse and risk analysis for completeness.
Statistical data from the Clinico-morphological Registry at VP Komisarenko Instituteof Endocrinology and Metabolism (IEM) of the National Academy of Medical Sciences of
Ukraine in Kiev indicate that from 1986 to 2010 a total of 6,798 cases of thyroid cancer havebeen diagnosed, of which 5,044 (74.2%) in those who were children aged 0-14 years, and
1,642 (24.2%) adolescents aged from 15 to 18 years at the time of accident and also 112(1.6%) cases of exposure in utero [ref. 61 and Chapter 3 of this book].
In Belarus, during the period from January 1985 to December 2006, 14,147 patientswith primary thyroid cancer were diagnosed and treated in Thyroid Cancer Center in Minsk[62]. During over than 20 years of observations after the Chernobyl accident, the crude
standardized incidence of thyroid cancer increased from 1.3 to 8.8 per 105 individuals.
Within last five years, the number of primary thyroid cancers in patients aged 19-45 did
not grow significantly. In contrast, patients above 46 years old demonstrate an increasing
incidence. These tendencies are currently seen in both heavily and less contaminatedregions of the country.
In Russia, according to currents data from the National Radiation Epidemiological
Registry (former Russian National Medical Dosimetric Registry), a total of 9,120 thyroid
cancer cases were registered for the period from 1981 to 2008 in the population of allages from the four regions officially recognized as contaminated. In 1981-1986, 102
thyroid cancer cases were registered annually on average. By contrast, during 2002-2008
the number of detected thyroid cancer cases was growing with the maximum of 592
cases observed in 2008 thus displaying a 6-fold increase. During the pre-accident andlatent periods, the crude incidence rate of thyroid cancer was 7.7 for males and 37.8 forfemales while for 2002-2008 it was 36.1 and 170.4, respectively, per 106 individuals. In acohort of 309,130 residents of contaminated areas followed-up from 1991 to 2008 forwhom individual thyroid doses were reconstructed, 993 cases of thyroid cancer werediagnosed. Of them 978 cases were histologically verified; 247 cases were in children andadolescents and 746 cases in adults [63]. Of note, the analysis in children and adolescentsubgroup demonstrated a shift of the distribution functions towards the cases withthe higher doses which may be indicative of radiation-related risk. Indeed, calculations
indicated that a statistically significant ERR of thyroid cancer incidence is found in thissubgroup with an estimate of 3.22 per 1Gy.
The tendencies in thyroid cancer incidence in different age groups of the residents ofcontaminated territories for Ukraine [61] and Belarus [64] are shown in Fig. 1.4. Despite thepatterns between the countries may vary in details, common trends could be seen: peak
incidence in childhood patients occurred in 1995-97, in adolescents in 2001-2004, and in
adults a gradually increasing incidence is observed.
12

Overview of the Chernobyl accident and its consequences

Figure 1.4. Incidence of thyroid cancer in Ukraine, in 6 most contaminated and 21 lesscontaminated regions of the country, and in Belarus (for comparison) in different age groups ofpatients diagnosed during 1986-2006. Data for Ukraine are from ref. [61], for Belarus data are derived
from ref. [64]. Lines comprise polynomial best-fit of data for easier visualization.

Regarding radiation-related risk, it is well proven that such does exist in exposedchildren and adolescents while the question still remains open for exposed adults. It has
been proposed, with reservations, that radiation excess of thyroid cancers may be observedin the group of population exposed at older ages as well as that latency of thyroid cancer
may be proportional to age in adult cancer patients subjected to radiation therapy [65].
At present, however, there is no strong evidence of radiation-related excess risk in theresidents of contaminated territories exposed in adult age.
To summarize the chapter, here we overviewed the major aspects of the accident at the
CNPP, and its radiological and health consequences with a particular focus on thyroid cancer.
As a result of massive radioactive releases, large groups of population received radiation
doses. These include clean-up workers and general population which was either evacuatedfrom the settlements in the vicinity of CNPP shortly after the accident or continued tolive in the territories of Ukraine, Belarus and Russia which were contaminated by fallouts.
Health consequences were initially difficult to forecast. Besides of deterministic effects ofacute exposure to ionizing radiation in firemen, information about contamination levelsof the affected territories, spectrum of pollutant radionuclides and doses accumulated by
13

Chapter 1

the residents were completely unknown. That is why, after first several years of domestic
efforts, large scale international collaborations were initiated to address nearly any
related problem, involving many governmental and non-governmental organizations
from a number of countries and from the world-wide community. Through cooperative
investigations, health status and dosimetric data were obtained to provide a ground forassessing the consequences. First reports about the increase of thyroid cancer incidence
in children and adolescents in Belarus and in Ukraine [66,67] were met cautiously by theexperts because of doubts in the accuracy of diagnosis, too short period of latency (which
would expected to be about 10 years as seen from A-bombing of Hiroshima and Nagasaki)
and insufficient evidence of link between Chernobyl radiation and cancer outbreak. With
time, however, essential proofs were found and efforts of both health authorities in thethree most affected countries and of the international parties could be focused on thehigh-risk groups and through more specialized means.
The accident at CNPP allowed learning a number of lessons such as that a disaster in one
country may affect other, that appropriate handling of vital information about and better
preparedness to radiation-involving accidents may bring about less adverse consequences,that international collaboration even on delicate issues could be established and it canbe effective. In the medical area, a large experience has been accumulated, including theunderstanding of the possibility of very short period of latency for thyroid cancer after
internal exposure to radioiodine, and how to diagnose and treat young patients withthyroid cancer.
In conclusion, while major health effects of the Chernobyl accident have become clearer
after 27 years that passed, we are still far from understanding of all the consequences, evenapplicably to thyroid cancer. As shown recently in A-bomb survivors of Japan, the excess
thyroid cancer risk associated with irradiation in childhood remained detectable over 50
years after exposure [68]. It therefore is essential to continuously and consistently observeliquidators and exposed population to achieve higher level of knowledge of radiation
effects after Chernobyl.
This chapter is an updated and modified version of our review article published earlier[69].

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Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bank

Chapter2

I Likhtarov, L Kovgan, S Masiuk,
M Chepurny, O Ivanova, V Gerasymenko,
M Tronko, T Bogdanova, GA Thomas

Different levels of thyroid dose individualizationof the Ukrainian donors in Chernobyl tissue bankIn order to accumulate and centralize information on the radioinduced Chernobyl
thyroid cancers, an international Chernobyl Tissue Bank (CTB) has been established. By
2012, it comprised 2,267 specimens of thyroid tumoral tissues from residents of Ukraine
who had been operated on within the time period from 1990 to 2011 (see Chapter 6).
These specimens were verified by experts in the course of 20 international panel meetings.
The specimens accumulated in the CTB represent a material of paramount importance forvarious studies of the effects of ionizing radiation exposure at the molecular and genetic
levels.
Over the last 25 years elapsed after the Chernobyl catastrophe, substantial experience
was accumulated in the field of the individual thyroid and other organs doses reconstruction
due to the accidental exposure. At that, in the ecological-dosimetry models, the reliability
and adequacy of the resulting doses entirely depend on the available data (the levels
and dynamics) of radioactive fallout on the soil, vegetation, milk, and other foodstuffs indifferent regions, as well as the information on the life style of residents during the time
period of exposure (their movements over the radioactively contaminated area, dietcomposition, and amount of foodstuffs being consumed). The results of more than 150,000
direct measurements of 131I activity in the thyroid of children and adolescents, which were
performed in May-June of 1986 in the northern, most contaminated regions of Ukraine, areparticularly important for the development of thyroid reconstruction models.
The results of direct measurements of thyroid activity that were performed in May-June
1986 are very helpful both to estimate the individual thyroid doses for the subject underthe measurement and to development and parameterization of the reconstruction models.
Hence, the four-level system of thyroid dose reconstruction was developed so that to estimate
the internal thyroid doses for individuals or population groups of all regions of Ukraine. Thissystem has been applied for the CTB donors’ thyroid doses reconstruction. The decision on whichlevels of the four-level system is to be used for a CTB subject depends on the available informationon the existence of direct measurement in 1986 and place of living (settlement, raion and oblast)in 1986. In all cases, the thyroid dose estimates either directly used the result of measurement
performed for the subject, or indirectly used the results of thyroid measurements performed
for other inhabitants in the settlements of raion in the form of relationships between the resultof thyroid measurements in different age-gender groups and environmental characteristics.
19

Chapter 2

Individual thyroid doses were estimated in 2009-2011 for 1,933 of 2,267 Ukrainian CTB
subjects [1] in the framework of EU Contract 211712 “CTB - The Chernobyl Tissue BankCoordinating International Research on Radiation Induced Thyroid Cancer”. For each subject
the central (deterministic) value of the thyroid dose was estimated and also the uncertainty
of such estimates, which are due to different types of errors in the parameters of theecological and biokinetic models that were used.
The objectives of this chapter are to present:•• the subdividing CTB cohort over the Groups and subgroups depending on the available
individual data and characteristics;•• a brief description of the dosimetry models that were used for the reconstruction ofindividual thyroid doses of Ukrainian CTB subjects of different Groups and subgroups,
as well as a description of the approaches used to assess the uncertainties attached tothe dose estimates for the subjects of the different groups;•• the generalized results of the dose estimates provided for the Ukrainian CTB subjects.
Geographical distribution of the subjects
It was found that in May-June of 1986, the CTB subjects were distributed over 24 oblastsof Ukraine and Crimea autonomous republic (Fig. 2.1). At that about 60% of the exposed
UkrCTB subjects resided in areas of highly-contaminated northern oblasts (Kyiv, Chernihiv,
and Zhytomyr), whereas 16% of CTB-subjects resided in areas with moderate levels ofradioiodine fallout, and 23% of Ukrainian CTB subjects resided in areas with low levels ofradioiodine fallout. In addition, there were 9 subjects who did not reside in Ukraine at thetime of the accident.
Types of exposure condition
Ukrainian CTB cohort may be subdivided according to the following exposure conditions:•• Subjects aged one year or more at the time of the accident exposed as a result ofradioactivity-contaminated foods consumption in 1986.
•• Subjects aged less than one year at the time of the accident exposed as a result of breast
feeding in May-June 1986.
•• Subjects born in May-June 1986 who have been exposed partly in utero, and partly as aresult of breast feeding.
•• Subjects born within the time period from July 1986 to March 1987 exposed in utero.
•• Non-exposed subjects born after March 1987.
Distribution of the UkrCTB subjects by age at the time of the accident
For a unit of 131I intake due to the consumption of contaminated foods the dose to thechild’s thyroid exceeds the dose to adults. This is mainly because the significantly smaller
size of children’s thyroid gland, in comparison to that for adults [2]. Thus, the age at whichchild’s exposure occurred is one of the critical parameter in the dose reconstruction. Table
2.1 shows the distribution of the UkrCTB subjects by age at the time of accident.
20Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bankFigure 2.1. Geographical distribution of the Ukrainian CTB subjects over the settlementsof different types in the oblasts with high, moderate and low 131I Chernobyl grounddeposition.
Table 2.1
Distribution of Ukrainian CTB subjects by age at the time of the accident
Age, years

Number of UkrCTB subjects
boys

girls

<1

87

39

1–4

327

84

5–9

366

73

10 -14433

127

15 – 17

256

59

18

32

10

Total exposed

1501

392

Born after March 1987

294

80

Total for the UkrCTB cohort

1795

472

21

Chapter 2

In Ukrainian CTB cohort 64 subjects were exposed in utero. The thyroid dose to the fetus
depends to a large degree on the level of 131I intake by the mother due to consumption offood, as well as on the embryo and fetus gestational age (period of mother’s pregnancy)
during exposure. The greater was the gestational age during the exposure period (from 26
April to 30 June 1986), the higher was the fetal dose per unit of 131I intake by the mother[3]. Table 2.2 presents the distribution of the Ukrainian CTB subjects who were exposed inutero according to the period of mother’s pregnancy at the time of accident.
Table 2.2
Distribution of in utero exposed UkrCTB subjects according to the period of mother’s
pregnancy at the time of the accident
Period of mother’s pregnancy on 26 April 1986 (days)

Number of subjects

<0

9

1-30

5

31-60

7

61-90

5

91-120

4

121-150

6

151-1809181-200

2> 200 (subjects born before July 1986)

17

Total

64

Distribution of Ukrainian CTB subjects by method of thyroid dose reconstruction
In the thyroid dose system that is used for the СТВ (TDS-CTB) all CTB subjects were
subdivided into several groups depending on the availability of direct measurements in1986 performed either directly on the subject, or on other persons in the region of his (her)residence at the time of accident.
Group 1. CTB subjects who had a direct thyroid measurement performed in May-June
1986 and were administered a special interview concerning the consumption rate ofcontaminated foods (essentially cow milk and leafy vegetables), as well as their possible
changes of residence in May-June 1986 [4]. The interviews of these subjects were performedin framework of Ukraine-U.S. cohort study [4,5].
Group 2. CTB subjects who had individual direct thyroid measurements carried out in
May-June 1986 [6], but without personal interviews.
Group 3. CTB subjects with neither individual direct thyroid measurements in May-June
1986 nor personal interviews. These subjects are further subdivided into three subgroups
depending on their residence or non-residence in the raions of different oblasts where
direct measurements were performed among the local population.
Subgroup 3.1 CTB subjects who resided in May-June 1986 in the settlements where
direct thyroid measurements were performed on some inhabitants (settlement of type 1).
22

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bank

Subgroup 3.2 CTB subjects who resided in the settlements where no direct thyroid
measurements were performed, but such measurements were performed on someinhabitants of neighboring settlements of the raion (settlement of type 2).
Subgroup 3.3 CTB subjects who were residents of the regions (raions, oblasts) where
direct thyroid measurements were not carried out at all (settlement of type 3).
Group 4. CTB subjects who were exposed in utero. This group includes those born within
the period from April 26, 1986 to March 31, 1987.
The distribution of the CTB subjects into the four groups is presented in Table 2.3.
Table 2.3
Distribution of CTB subjects by the groups and subgroups
Description of dosimetry group

Number of UkrCTB
subjects*

Group 1

CTB subjects who had direct thyroid measurements and personal interviews

165Group 2

CTB subjects who had direct measurementsof 131I in the thyroid in May-June of 1986 but
had no personal histories

19

Group 3

CTB subjects who had neither personal histo-

1685

Dosimetry group andsubgroup

ries nor direct measurements ofSubgroup 3.1
Subgroup 3.2
Subgroup 3.3
Group 4

I activity in131

thyroid in April-June of 1986:- residents of settlementsof type 1- residents of settlementsof type 2- residents of settlementsof type 3

1029

CTB subjects who were exposed in utero

64

613
43

Non-irradiated

310

Total

2243

For 24 CTB-subjects the settlement of their residence in 1986 could not be identified*

Table 2.4 shows the distribution of the Ukrainian CTB subjects of four above-mentioned
groups according to date of birth: children, adults, and exposed in utero.
As shown in Tables 2.3 and 2.4, Group 3, consisting of 1,685 CTB subjects (mainly
children) is the most numerous.

23

Chapter 2

Table 2.4
Distribution of the CTB subjects of different groups according to date of birth
Date of birth
26.04.1968May-June 1986
26.04.1986
Exposed in utero +Childrenpostnatal

Dosimetrygroups of
CTB cohort

before26.04.1968

Group 1

-

165

-

-

165

Group 2

-

19

-

-

19

Group 3

43

1642

-

-

1685

Group 4

-

-

17

47

64

Total

43

1826

17

47

1933

AdultsJuly 1986 March 1987
Exposedin utero

Total
NumberMembers of Groups 1 and 2 (~9.5% of all irradiated Ukrainian CTB subjects), for whom
information on direct measurements of radioiodine activity in the thyroid in May-June
1986 is available, have the highest degree of dose individualization.
Because the members of Group 3 had no direct thyroid measurements in 1986, a mean
settlement-age-gender specific dose is assigned to subjects of these groups. The adequacyof estimate of mean group-specific dose depends whether the direct thyroid measurements
were provided in the settlement of residence of the subject or in a neighboring settlement.
Thus, the highest degree of adequacy of an individualized dose estimations have themembers of subgroup 3.1 residing in 52 settlements of type 1, and then, in the descendingorder, the members of subgroups 3.2 and 3.3 who were residents of 27 and 486 settlementsof types 2 and 3, respectively. The distribution of settlements of different types in which
CTB subjects were residing in 1986, for different oblasts of Ukraine, is shown on Figure 2.1.
Settlements of type 1 and 2 are located predominantly in the most contaminated northernoblasts, while settlements of type 3 are located in the less contaminated southern oblasts.
General structure of models in TDS-CTB
Figure 2.2 shows the structure of the four-level TDS-CTB used to calculate the thyroid
doses for the subjects of each of four groups as well as the common and group-specificinitial data sets used in the calculation models of each level.
As shown in Figure 2.2, the data on the daily fallouts of 131I on the ground in thesettlements of residence are used as input in the TDS-CTB models of each of four groups.
Daily fallouts over the 10 days of accidental release for each settlement are estimatedusing a model of atmospheric transfer [7, 8], allowing to calculate the daily dynamics of 131I
concentrations in vegetation and milk during May-June 1986.

24

I release andmeteorological
data

131

137
Cs depositionin the settlementsof residence of thesubject's mother(settlements oftype 3)25

Figure 2.2. General scheme of models and initial data sets used in the different dosimetry groups in TDS-CTB.

Figure 2.2. General scheme of models and initial data sets used in the different dosimetry groups in TDS-CTB

Individual direct
thyroid
measurement in
the surrounding
settlements(settlements oftype 2)

Individual direct
thyroid
measurement in thesettlements ofresidence of thesubject's mother(settlements oftype 1)

set of initial empirical data used as modifiers for the different dosimetry groups

Individual
instrumental
thyroid
dose

Ecologicaltimeintegrated
131
I
thyroidal
activity

Relative timeintegrated
thyroidal
activity for
different agegender groups
fa,sEntire set(150 000) of
directthyroid
measurements-

Cs depositionin the settlementsof residence of thesubject(settlements oftype 3)137

Subgroup 3.3

Individual direct
thyroid
measurement in
the surrounding
settlements(settlements oftype 2)Subgroup 3.2

Model ofdietGroup 3

Atmospherictransport model

set of calculation models

Individual
directthyroid
measurement

Individual direct
thyroid
measurement in thesettlements ofresidence of thesubject(settlements oftype 1)Subgroup 3.1

Time variationof 131I on the
ground andvegetation-

Individual
instrumental
thyroid
dose

Ecologicaltimeintegrated
131
I
thyroidal
activity

Individual
directthyroid
measurement

Ecologicaltimeintegrated
131
I
thyroidal
activity

Individual
instrumental
thyroiddose

Model ofdiet

Model ofdietGroup 2

Personal
interviewGroup 1Time variation of
131
I in milk andleafy vegetables

Individual
instrumental
thyroiddose of
CTBsubject

Timevariationof 131I
mother's
intakeModel of dietfor motherGroup 4

Transfercoefficientfrom 131I
mother’s
intake goembryo/fetus
dose(ICRP-88)

10

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bank

Chapter 2

Table 2.5
Reference daily consumption rates of milk and leafy vegetables used in the TDS-CTB forGroups 2, 3, and 4; AM and STD are the arithmetic mean and standard deviation, respectively
Rural areas
Age

Boys
AM

26

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

0.67
0.66
0.64
0.63
0.69
0.69
0.65
0.70
0.73
0.79
0.77
0.72
0.78
0.78
0.72
0.83
0.83
0.83

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

0.011
0.015
0.019
0.021
0.025
0.029
0.027
0.029
0.028
0.037
0.036
0.035
0.039
0.036
0.044
0.038
0.046
0.046

Urban areas

Girls
Boys
AM
STD
AM
STD
-1
Milk consumption rate (L d )
0.42
0.62
0.46
0.48
0.33
0.44
0.57
0.38
0.33
0.27
0.46
0.52
0.38
0.34
0.28
0.39
0.58
0.37
0.36
0.38
0.47
0.52
0.41
0.39
0.41
0.47
0.57
0.40
0.31
0.28
0.45
0.50
0.36
0.32
0.23
0.55
0.49
0.36
0.35
0.35
0.61
0.52
0.41
0.30
0.33
0.60
0.45
0.39
0.37
0.39
0.58
0.40
0.33
0.46
0.57
0.57
0.48
0.50
0.47
0.41
0.65
0.47
0.51
0.47
0.62
0.65
0.47
0.41
0.44
0.35
0.62
0.43
0.36
0.44
0.50
0.74
0.48
0.40
0.44
0.50
0.66
0.44
0.37
0.44
0.50
0.66
0.44
0.37
0.44
0.50
Consumption rate of leafy vegetables (kg d-1)
0.014
0.010
0.011
0.014
0.017
0.021
0.013
0.019
0.013
0.017
0.020
0.017
0.020
0.012
0.013
0.018
0.022
0.024
0.020
0.024
0.022
0.017
0.017
0.019
0.017
0.025
0.023
0.021
0.025
0.024
0.025
0.027
0.022
0.020
0.026
0.028
0.029
0.026
0.020
0.020
0.020
0.026
0.027
0.024
0.030
0.032
0.033
0.025
0.031
0.031
0.031
0.032
0.025
0.032
0.036
0.027
0.036
0.031
0.028
0.026
0.029
0.030
0.023
0.026
0.018
0.032
0.031
0.030
0.035
0.031
0.031
0.036
0.027
0.027
0.022
0.028
0.044
0.041
0.027
0.022
0.032
0.035
0.028
0.027
0.022
0.032
0.035
0.028
0.027
0.022
STD

Girls
AM

STD

0.40
0.33
0.29
0.30
0.30
0.29
0.30
0.29
0.21
0.21
0.25
0.23
0.27
0.20
0.20
0.20
0.20
0.20

0.32
0.28
0.28
0.25
0.22
0.21
0.25
0.35
0.16
0.18
0.28
0.21
0.23
0.19
0.29
0.29
0.29
0.29

0.007
0.015
0.014
0.017
0.017
0.024
0.025
0.018
0.023
0.020
0.037
0.034
0.038
0.042
0.033
0.033
0.033
0.033

0.006
0.017
0.018
0.020
0.016
0.028
0.021
0.017
0.019
0.018
0.038
0.028
0.037
0.036
0.032
0.032
0.032
0.032

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bank

The “ecological” time-integrated thyroid activity of 131I is calculated for the subjectsof Groups 1, 2 and 3 using the time-variation of 131I in leafy vegetables and milk and also
the model of diet.
For the subjects of Group 1 the model of diet was developed using the informationfrom the personal interviews [4] on the daily consumption of different components ofdiet: cow milk, goat milk, private milk, shop milk, sour milk, kefir, and leafy vegetables. The
information on the settlements of residence in May and June 1986, duration of his (her)stay in each residence, dates of arrival/departure from each settlement of residence wasalso clarified during the personal interviews of the CTB subjects of Group 1.
Due to the absence of personal dietary data for the subjects of Groups 2, 3, and 4, thereference age- and gender-dependent consumption rates of milk and leafy vegetables
were used for the calculation of the 131I daily intake (Table 2.5). It was also assumed thatthe subjects of Groups 2, 3, and 4 were not relocated from their settlements of residence
in April-June 1986.
Group-specific modifiers are established for the ecological time-integrated 131I thyroidal
activity are also shown in Figure 2.2 for each group.
The following initial data sets were used for establishing the modifiers:•• subjects of Group 1 and 2: the results of direct thyroid measurements of 131I activity for the
CTB subject in May-June 1986;•• subjects of subgroup 3.1: the results of direct thyroid measurements of 131I activity
performed in May-June 1986 among the inhabitants (not the CTB subjects) in thesettlement of staying of the CTB subject (settlement of type 1);•• subjects of subgroup 3.2: the results of direct thyroid measurements of 131I activity performed
in May-June of 1986 among the inhabitants in the settlements of the raion surrounding
the settlement of residence of the CTB subject in 1986 (settlement of type 2);•• subject of subgroup 3.3: data on 137Cs ground deposition in the settlement of residence of
the CTB subjects (settlement of type 3).
The modifiers of subgroups of Group 3 are developed by analyzing the results of~150,000 direct thyroid activity measurements taken in May-June 1986 in the Northernoblasts of Ukraine.
The model of thyroid dose reconstruction applied for the subjects of Group 4 (exposed
in utero) includes the calculation of time-variation of 131I intake for mother. At that themodifiers are dependent on the type of settlement of a CTB-subject’s mother’s residence in 1986.
Using the ecological time-integrated 131I thyroidal activity corrected by the correspondent
modifiers and age-gender dependent thyroid mass [9], the individual “instrumental”
thyroid doses (in deterministic and stochastic modes) are calculated for each CTB subjectof Groups 1, 2 and 3. The individual “instrumental” thyroid doses for the subjects of Group
4 are calculated using the transfer coefficients from 131I mother’s intake to embryo-fetus
dose, which are significantly changing with the period of mother’s pregnancy [3].
Parameters of models in TDS-CTB
The central estimates and uncertainty distributions that were selected for the main
parameters of the ecological and dosimetry models in TDS-CTB are presented in Table
2.6, with the exception of age-dependent lung ventilation rate and biological half-time ofiodine excretion from the thyroid, which are provided in Table 2.7.
27

Chapter 2

Table 2.6
Central estimates and statistical characteristics of the distributions of the main parameters
used in TDS-CTB. GM is the geometric mean; GSD is the geometric standard deviation [8,10-18]

28

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bankContinuation of Table 2.6

Table 2.7
Central estimates and ranges of age-dependent parameters in TDS-CTB: lung ventilation
rate and biological half-time of iodine excretion from the thyroid [2,12,19]
Lung ventilation rate

Age(years)
a
0
1
2
3
4
5
6
7
8
9
10
11

Biological half-time of iodine excretion from the thyroid (d)(m ·d )
3

AM
2.9
5.6
6.5
7.4
8.3
9.3
10.4
11.5
12.6
13.6
14.8
16

min
1.4
2.7
3.1
3.5
3.9
4.4
4.9
5.4
5.9
6.4
7.0
7.5

-1

max
5.4
10.6
12.3
14.0
15.6
17.5
19.6
21.7
23.7
25.8
28.0
30.2

AM
15
20
22
25
28
30
38
46
54
62
70
72

min
7.1
9.4
10.4
11.8
13.2
14.2
18.0
21.7
25.5
29.3
33.1
34.0

max
28
38
42
47
53
57
72
87
102
117
132
136

29

Chapter 2

Continuation of Table 2.7
Lung ventilation rate

Age(years)
a
12
13
14
15
16
17
18

Biological half-time of iodine excretion from the thyroid (d)(m3·d -1)
AM

min

max

AM

min

max

17.2
18.3
19.5
20.3
20.7
21.2
21.6

8.1
8.7
9.2
9.6
9.8
10.0
10.2

32.4
34.7
36.9
38.4
39.2
40.0
40.8

74
76
78
80
82
84
87

35.0
35.9
36.9
37.8
38.7
39.7
41.1

140
144
147
151
155
159
164

Main equations of TDS-CTB for the subjects of different groups
Groups 1 and 2
The following equation was developed to calculate the individual dose
i of dosimetry group 1 or 2:30

for subject

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bank

31

Chapter 2

Table 2.8
Parameters of the relative time-integrated thyroidal 131I activity function fa,s for different
age-gender groups. GM is the geometric mean; GSD is the geometric standard deviation

Age
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

Relative time-integrated thyroidal activity (fa,s)Urban areas
Rural areas
Girls
Boys
Girls
Boys
GM
GSD
GM
GSD
GM
GSD
GM
GSD
0.81
3.3
0.61
3.0
0.58
3.1
0.47
3.2
0.81
3.3
0.61
3.0
0.58
3.1
0.47
3.2
0.81
2.8
0.62
3.0
0.64
2.8
0.55
2.8
0.77
2.5
0.61
2.8
0.64
2.7
0.54
2.6
0.86
2.4
0.67
2.5
0.70
2.6
0.56
2.9
0.97
2.5
0.86
2.5
0.70
2.6
0.59
2.6
1.0
2.3
0.86
2.3
0.77
2.5
0.66
2.6
1.0
2.1
0.85
2.3
0.75
2.2
0.70
2.4
0.88
2.4
0.79
2.4
0.76
2.4
0.72
2.5
0.91
2.2
0.81
2.2
0.80
2.4
0.79
2.4
0.92
2.2
0.81
2.2
0.81
2.4
0.84
2.2
0.97
2.1
0.91
2.1
0.89
2.2
0.85
2.3
0.95
2.1
0.94
2.1
0.95
2.1
0.90
2.2
1.0
2.1
0.96
2.2
1.0
2.1
1.0
2.2
1.1
2.1
1.1
2.2
1.0
2.1
1.1
2.2
1.1
2.2
1.1
2.3
1.0
2.3
1.2
2.4
1.2
2.4
1.1
2.5
1.0
2.4
1.3
2.5
1.2
2.5
1.1
2.3
1.0
2.4
1.1
2.4
1.1
2.8
1.0
3.0
0.95
2.7
1.1
2.1

Subgroup 3.2 (Settlements of type 2, j**):32

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bank

Location

Rural
Urban

Gender

B

β

GM

GSD

AM

STD

Boys

0.59

1.1

0.36

1.03

Girls

0.47

1.1

0.36

1.03

Boys

0.36

1.5

0.61

1.10

Girls

0.34

1.5

0.58

1.10

33

Chapter 2

Estimation of thyroid dose uncertainties for the UkrCTB subjects
The uncertainties of the thyroid doses estimations in the CTB subjects of different
dosimetry groups were calculated using a Monte-Carlo procedure. For this purpose,probability distributions were assigned to most of parameter values. The types andcharacteristics of the distributions of some of the parameters are shown in Table 2.6. It
was assumed in the Monte-Carlo procedure that all parameters were independent. One
thousand values of the individual dose were calculated for every CTB subject. Finally, thearithmetic and geometric means of the 1,000 values of instrumental doses as well as thegeometric standard deviation minimum, maximum and 25%, 50%, 75% percentiles ofthese distributions were estimated for every CTB subject.
The Monte-Carlo procedure used for estimating the dose uncertainties differed in somerespect for the different groups and subgroups, since different parameters and functions
were applied.
Estimates of individual thyroid doses for the UkrCTB subjects
Individual thyroid doses were estimated for 1,933 Ukrainian CTB subjects. Doses havenot been reconstructed for 24 CTB subjects (because the settlements of their staying in
1986 could not be identified), and for 310 non-irradiated subjects born after March 1987.
For each of the subjects the thyroid dose and their uncertainties were estimated fromthe environmental transport and biokinetic models adapted to the information available forthe different groups and subgroups (Figure 2.2) using a Monte-Carlo simulation procedure
with 1,000 trials for every CTB subject.
Table 2.10 shows the arithmetic mean as well as the 50%, 25%, 75% percentiles and theminimum and maximum values of individual doses estimated for the subjects of different
34Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bankage-groups in different dosimetry groups. For 15 of the 64 subjects of Group 4, theindividual thyroid doses are estimated to be negligibly small, and taken to be equal to zero.
Table 2.10
General groups of individual thyroid doses estimated for the UkrCTB subjects of thedifferent groups and subgroups
Age intervals,
years

Individual thyroid doses, Gy
Percentiles
Min
50%
25%
75%

Number of
subjects

Mean

44
42
69
10
165

1.9
1.2
0.75
1.6
1.2

0.43
0.16
0.055
0.045
0.13

0.81
0.54
0.31
0.25
0.48

2.3
1.8
1.1
2.5
1.4

0.046
0.025
0.001
0.023
0.001

13
7.2
5.3
8.5
13

13
3
2
1
19

2.7
0.033
0.33
0.3
1.9

0.43
0.028
0.021
0.3
0.099

0.72
0.032
0.33
0.3
0.53

3.8
0.037
0.63
0.3
3.2

0.008
0.027
0.021
0.3
0.008

13
0.039
0.63
0.3
13

164
159
186
104
613

0.26
0.096
0.049
0.037
0.12

0.1
0.039
0.024
0.024
0.027

0.15
0.051
0.03
0.026
0.043

0.23
0.068
0.034
0.028
0.11

0.04
0.021
0.013
0.014
0.013

5.2
2.7
1.1
0.37
5.2

16
5
13
9
43

2
1.4
0.1
0.031
0.93

0.09
0.017
0.021
0.013
0.028

0.15
0.2
0.075
0.027
0.091

0.91
3
0.14
0.035
0.19

0.04
0.016
0.014
0.011
0.011

24
4.1
0.44
0.091
24

293
223
283
229
1029

0.3
0.061
0.033
0.029
0.09

0.036
0.014
0.008
0.008
0.012

0.11
0.034
0.017
0.017
0.031

0.21
0.068
0.037
0.031
0.08

0.001
0.002
0.001
0.001
0.001

1.9
0.8
0.45
0.59
1.9

49

0.1

0.001

0.014

0.08

<0.001

2.1

MaxGroup 1
0-4
5-9
10-14
15+
All ages
Group 2
0-4
5-9
10-14
15+
All ages
Subgroup 3.1
0-4
5-9
10-14
15+
All ages
Subgroup 3.2
0-4
5-9
10-14
15+
All ages
Subgroup 3.3
0-4
5-9
10-14
15+
All ages
Group 4
All ages

35

Chapter 2

The results presented in Table 2.10 indicate that the highest doses were estimated for
the CTB subjects of dosimetry groups 1 and 2, and also for the subjects of subgroup 3.2.
The high doses in the subjects of these groups and subgroups are the consequence of theirresidence in May-June 1986 in the most radioactively-contaminated areas (Figure 2.1). The
lowest doses are estimated for the subjects of subgroup 3.3 because these subjects werestaying in the areas with moderate and low radioactive contamination in 1986. As shownin Table 2.10, the younger children (aged 0 to 4 years) received higher thyroid doses thanany other age group in all dosimetry groups and subgroups.
The general characteristics of the uncertainties of the estimated individual thyroid doses
are presented in Table 2.11 in terms of mean, min, max and geometric standard deviation(GSD) of individual geometric standard deviation for the different groups and subgroups.
The data of Table 2.11 clearly show that the uncertainties in the reconstructed individual
thyroid dose estimates increase from Group 1 to Group 4. In dosimetry Group 3, the highest
uncertainties in the estimated individual doses were found for the subjects of subgroup
3.3. This is due to the fact that direct thyroid measurements of 131I activity are not used tojustify the ecological dose estimation for this subgroup. The substantial uncertainties in the
thyroid dose estimates for the CTB subjects exposed in utero (Group 4) are related to: (1) thecomplexity of modeling the iodine metabolism in the embryo/fetus and the transfer of 131I
from the mother to fetus at different stages of pregnancy, and (2) a number of difficulties inmodeling the mother’s diet in May-June 1986.
Table 2.11
Average values of geometric standard deviation (GSD) of individual geometric standard
deviation for the subjects of diferent groups and subgroups. N is the number of subjects
Dosimetry group andsubgroup

N

1
2
3-1
3-2
3-3
4

165
19
613
43
1029
49

GSD of individual thyroid doses
Mean
Min
Max
1.5
1.3
4.7
1.5
1.4
1.7
2.9
2.3
4.6
3.3
2.3
5.2
3.6
3.1
4.5
3.8
2.8
8.7

Table 2.12 presents the distribution of the Ukrainian CTB subjects of different dosimetrygroup/subgroup over the intervals of individual thyroid dose irrespectively of the age. As
shown in Table 2.12, the CTB members of Group 1 are distributed rather evenly by dosevalue within the interval up to 5 Gy. Individual doses for 17 of 19 members of Group
2 are also within the dose interval up to 5 Gy. In subgroup 3.1 for 99% of subjects theestimated individual thyroid doses do not exceed 1 Gy, and for about 55% of membersof this group the thyroid doses do not exceed 0.05 Gy. In the subgroup 3.2 the relative
distribution of the subjects by the dose interval is similar to that in subgroup 3.1. For
97% of members of subgroup 3.3 the individual thyroid doses were estimated to be lessthan 0.5 Gy, and for 79% as being less than 0.1 Gy. For 47 of 64 Ukrainian CTB members
36

Different levels of thyroid dose individualization of the Ukrainian donors in Chernobyl tissue bankof Group 4, i.e., those who were partly or entirely exposed in utero, individual thyroid doses
were estimated to be less than 0.05 Gy. For one subject of Group 4 the individual thyroid
dose estimation is greater than 0.5 Gy.
Table 2.12
Distributions of UkrCTB subjects according to the interval of estimated mean individual
thyroid doseGroup and Subgroup

Thyroid doseinterval, Gy

1

2

<0.05
0.05-0.1
0.1-0.2
0.2-0.5
0.5-1
1-2
2-5
5-10
>10
Entire cohort

23
12
15
36
24
22
27
4
2
165

5
4
4
4
1
1
19

3.1
3.2
Number of UkrCTB subjects
335
18
109
5
96
10
52
1
13
4
5
1
2
3
1
1
613
43

3.3

4

681
129
124
62
22
11
1029

47
9
2
5
1
64

References
1. Likhtarov I, Thomas G, Kovgan L, et al. Reconstruction of individual thyroid doses to the Ukrainian
subjects enrolled in the Chernobyl tissue bank. Rad Prot Dosim 2013; doi:10.1093/rpd/nct096 :1-17.
2. ICRP. Age-dependent Doses to Members of the Public from Intake of Radionuclides: Part 1 Ingestion dose coefficients. In: ICRP Publication 56. Oxford Pergamon Press; 1990.
3. Likhtarov I, Kovgan L, Chepurny M, et al. Estimation of the thyroid doses for Ukrainian children
exposed in utero after the Chornobyl accident. Health Phys 2011;100:583-593.
4. Likhtarev I, Bouville A, Kovgan L, et al. Questionnaire- and Measurement-Based Individual
Thyroid Doses in Ukraine Resulting from the Chornobyl Nuclear Reactor Accident. Radiat Res
2006;166:271–286.
5. Tronko M, Howe G, Bogdanova T, et al. A cohort study and other thyroid diseases after the
Chernobyl accident: thyroid cancer in Ukraine detected during first screening. J Natl Cancer Inst2006;98:897-903.
6. Likhtariov IA, Shandala NK, Gulko GM, Kairo IA and Chepurnoy NI. Exposure doses to thyroid of
the Ukrainian population after the Chernobyl accident. Health Phys 1993;64:594-599.
7. Talerko, N. Mesoscale modelling of radioactive contamination formation in Ukraine caused by
the Chornobyl accident. J Environ Radioact 2005;78:311-329.
8. Talerko, N. Reconstruction of 131I radioactive contamination in Ukraine caused by the Chornobyl
accident using atmospheric transport modeling. J Environ Radioact 2005;84:343-362.

37

Chapter 2

9. Likhtarov I, Kovgan L, Masiuk S, et al. Estimating thyroid masses for children, infants and fetuses
in Ukraine exposed to 131I from the Chornobyl accident. Health Phys 2013;104:78-86.
10. Cristy, M., Eckerman, K.F. Specific Absorbed Fraction of Energy at Various Ages from Internal
Photon Sources. ORNL/TM-8381/V1–7. Oak Ridge: Oak Ridge National Laboratory; 1987.
11. ICRP. Radionuclide Transformations: Energy and Intensity of Emissions. In: ICRP Publication 38.
Oxford Pergamon Press; 1983.
12. ICRP. Age-Dependent Doses to Members of the Public from Intake of Radionuclides: Part 2 Ingestion Dose Coefficients. In: ICRP Publication 67. Oxford Pergamon Press; 1992.
13. IAEA-TECDOC-857. Modelling of radionuclide interception and loss processes in vegetation andof transfer in semi-natural ecosystems. Second report of the VAMP terrestrial working group.
Vienna: IAEA; 1996.
14. IAEA-TECDOC-795. Validation of models using Chornobyl fallout data from the Central Bohemia
region of the Czech Republic. Scenario CB. First report of the VAMP Multiple Pathways Assessment
Working Group. Vienna: IAEA; 1995.
15. Barkhudarov RM, Gordeev KI, Dibobes IK, et al. Methodological principles for calculating levelsof external and internal exposure of the population used in taking strategic decisions. In:
Medical aspects of the Chernobyl accident. Proceedings of the conference in Kiev, 11-13 May
1988. Vienna: IAEA; 1989.
16. Simon S, Luckyanov N, Bouville A, VanMiddlesworth L and Weinstock RM. Transfer of I-131 into
human breast milk and transfer coefficients for radiological dose assessments. Health Phys
2002;82(6):796-806.
17. Prister BS. The problems of agricultural radioecology and radiobiology at radiation environmental
pollution by a young mixture of nuclear fission products. Kyiv: Chornobyl; 2008 (In Russian).
18. Izrael YA, Vakulovsky S M, Vetrov VA, et al. Chornobyl: Radioactive contamination of theenvironment. Gidrometeoizdat; 1990 (In Russian).
19. NRSU-97. Norms of radiation safety of Ukraine. Kyiv; 2003 (In Ukrainian).
20. Likhtarov I, Kovgan L, Vavilov S, et al. Post-Chornobyl thyroid cancers in Ukraine. Report 1.
Estimation of thyroid doses. Radiat Res 2005;163:125-136.
21. ICRP. Doses to the Embryo and Fetus from Intakes of Radionuclides by the Mother. In: ICRP
Publication 88. Oxford Pergamon Press; 2001.

38

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Chapter3

M Tronko, V Shpak, T Bogdanova, V Saenko,
S Yamashita

Epidemiology of thyroid cancer in Ukraine
after Chernobyl

Thyroid malignancies are relatively rare worldwide, yet their incidence has increased
over the last few decades [1,2]. Epidemiology of thyroid cancer in the population of Ukraine
exposed to radiation as a result of accident at the Chernobyl Nuclear Power Plant in April,
1986 is of a particular interest. Although the relationship between the Chernobyl radiationand increasing incidence of thyroid cancer among exposed children and adolescents in
Belarus, Russia, and Ukraine is established in a number of studies and is the main provenhealth consequence of the accident [3,4], a continued monitoring and analysis of temporal
trends of this disease have important medical and scientific impacts [5-7].
The purpose of this Chapter is to overview data on thyroid cancer incidence for theperiod from 1986 to 2010 in specific groups of population of Ukraine exposed in childhoodor adolescence and also prenatally (in utero). In addition, the group of subjects born after
the accident is included in the study because it provides important information on thyroid
cancer incidence in the population of Ukraine which had not experienced Chernobyl fallouts.
A tool for recording and storage of data on the incidence of any cancer are populationbased registries [8-11]; information can be used for subsequent analysis of morbidity andmortality in certain age groups and geographical areas. Domestic sources of data on thyroid
cancer incidence in Ukraine are the site-specific Clinico-morphological Registry (CMR) of
the State Institution “VP Komisarenko Institute of Endocrinology and Metabolism of the
National Academy of Medical Sciences of Ukraine” (IEM) [12], and a classic cancer registry,
which keeps records on all types of cancer, The National Cancer Registry of Ukraine (NCR)of the National Cancer Institute of the Ukraine Ministry of Public Health [13,14].
Specialized Clinico-morphological and National Cancer Registries of Ukraine
In the first half of the 1980-ies there were no personalized records of thyroid cancer cases
in Ukraine [15]. Statistical summary of thyroid cancer could be derived from the archivesof hospitals or from the reports of regional endocrinology services. After the Chernobyl
accident in 1986, the Ministry of Public Health of USSR recommended to establish
personalized registries of affected population and to improve recording system of patientswith thyroid diseases which were anticipated to be one of the possible health effects of theChernobyl accident [16,17]. In Ukraine, the collection of data on thyroid cancer incidence
39Chapter 3

was coordinated by the Institute of Endocrinology and Metabolism (IEM) with participationof regional endocrinology services.
In 1992, a personalized Clinico-morphological Registry was established at the IEM forthe first time in Ukraine, into which all cases of thyroid cancer in patients whose age at thetime of accident did not exceed 18 years (i.e., born in 1968 and later) were entered. Creationof the Registry was promoted by the initiative of the Ukraine Ministry of Public Health in
the Order No. 12 dated January 20, 1992 “On the improvement of endocrinological care
to children and adults with thyroid diseases” in which the need for an increased attention
to thyroid disorders after the Chernobyl accident and compulsory referral of children
and adolescents with such diseases for surgical treatment to the Clinic of the IEM wasformally stated. In addition, regional and municipal endocrinology and oncology clinics
were imposed to collect and report complete information about thyroid cancer cases incorresponding age group to IEM, and to provide histological slides of tumors for additional
expertise of the quality of pathomorphological diagnosis. Thus, IEM managed to collectthe necessary data for comprehensive registry functioning.
In the post-Chernobyl period, the CMR has been continuously providing statistics on thenumber of cases and incidence of thyroid cancer among children and adolescents to the
Ministry of Public Health and Academy of Medical Sciences of Ukraine, and also served as asource of data for a number of analytical studies on thyroid cancer incidence and assessmentof radiation risks of thyroid cancer in the younger age groups of Ukraine [3,5,6,12].
Statistical records of thyroid cancer as of a separate entity in the structure of oncologicalservices of Ukraine were started in 1989 [14,18]. At the same time, the Institute of Oncologyof the Academy of Medical Sciences of Ukraine launched an automated National Cancer
Registry (NCR) that covered all regions of Ukraine. NCR was based on a network of specialized
cancer institutions and a State system of cancer registration. Practical realization andimplementation of the information system in oncology at the regional level began in the
mid-’90-s receiving governmental support according to the Order of the Ukraine Ministryof Public Health “On the establishment of a National Cancer Registry of Ukraine” dated
December 30, 1996 [14]. In 2001, the creation of the system was completed by including all
regions of Ukraine in the Registry [13,14].
A close cooperation between the CMR and NCR began in 2005. Today, the CMR is insome way a part of NCR [19-21]. Note however, that cross-check of the registries reveals
some discordances. The CMR is a specialized Clinico-morphological Registry that includes
particular age group (at high risk for developing thyroid cancer) and only operated caseswith pathologically confirmed diagnosis. In contrast, besides the CMR records, National
Cancer Registry also includes cases that had not been operated with only preoperative
cytological conclusion about the possibility of thyroid cancer available. Moreover, thecalculation of cases at the regional level in the CMR is based on the patient’s place ofresidence at the time of Chernobyl accident, while the NCR system is based on the patient’s
place of residence at surgery. In other words, these differences should always be taken into
account when comparing the two data Registries or analyzing the incidence according todata of one or another registry.
Pathological verification of diagnosis is essential for the case to be included in the CMR.
The detailed pathological report including tumor type, subtype, invasive properties and40

Epidemiology of thyroid cancer in Ukraine after Chernobyl

tumor size is mandatory ​​for cases operated at the Department of Surgery of Endocrine
Glands of the IEM, and for the material (paraffin blocks, histological specimens) frompatients operated elsewhere in Ukraine yet receiving radioactive iodine therapy at the
Department of Clinical Radiology of the IEM (see Chapter 4).
Sources of information for the CMR are currently the reports of regional endocrinology
services, data of regional oncological institutions (via the NCR of Ukraine), and clinicalmedical information system (MIS) of the IEM (www.therdep.com.ua). The principles ofinclusion and recording of personal data coming from different sources correspond tothe classical rules and procedures of cancer registries [22-24]. Automated procedures andcontrol of completeness and quality of personal data play an important role [25].
Software realization of Clinico-morphological RegistryEntering and storage of Registry data is implemented using MS SQL Server software.
This•• ensures data integrity;•• allows the use of a standard relational model for designing data structures and typical
SQL for queries;•• provides a reliable import/export of data from most databases;•• allows performing application tasks using typical software tools (MS Access, Delphi,
C + +, *. net , etc.).
The upgraded structure of registry databases provides some additional features:•• supports both Ukrainian and Russian versions of patient’s surname and first name;•• implements a mechanism of saving changes or multiple patient’s attributes’ values ​​(e.g.
name, location, diagnosis);•• formalizes the place of residence according to the standard administrative territorial
codifier “KOATO”.
In addition, links have been established with databases with the geographicalcomponent at the regional, district and settlement level (MapInfo format), which extend
the capabilities of data analysis and allow building various thematic maps. Today, the logicalstructure of the Registry includes three functional components: CaseRegist, CaseManager,
and CaseReport.
•• CaseRegist is a module of primary registration of data reported by the regional
endocrinologists and IEM patients.
•• CaseManager is a module of analysis, linkage, and verification of the Registry information.
With this component, a comparative analysis of information from multiple sources
is conducted including the search for and removal of duplicate records. A verified
analytical version of the Registry record is generated that remains active for the year.
A list of problematic cases to be verified by an expert morphologist and/or refined
through queries to regional services could be created. The module also stores archivesof the versions of analytical tables of the Registry from previous years; information aboutchanges or refining of certain attributes of patients to be included in the next version of
the Registry is accumulated.
41

Chapter 3•• CaseReport component contains the current version of analytical tables of the Registry
and a set of typical queries to generate standard numerical tables, charts and graphsthat describe the available data for particular time and can be used for the preparationof reports, presentations, and publications.
The demographic component of the Clinico-morphological Registry
The demographic component of the Registry is based on a series of periodic publicationsof the State Statistics Committee of Ukraine; publications of regional statistics departments
may be also involved detailing certain parameters for a specific region.
Census data represent the most reliable and detailed source of information on Ukrainian
population. Our study period (from 1986 to 2010) includes two censuses: Ukrainian SSR
census of 1989 and the All-Ukrainian census of 2001 [26, 27].
Primary sources of demographic data also include publications on the distribution of
population by age and sex [28-33], the number of current and permanent population of
Ukraine at the regional level, and annual demographic data records.
General statistical collections and the official website of the State Statistics Committee(www.ukrstat.gov.ua) [34] may also be used as sources of current demographic information.
The demographic component of the Registry includes data on the population of Ukraine
for the period 1986 to 2010, and the following age groups are selected for monitoring:
••
••
••
••
••
••
••

children under 14 years old (born before 1987);
children under 14 years old (born in 1987 or later);adolescents aged 15 to 18 years (born before 1987);
adolescents aged 15 to 18 years (born in 1987 or later);adults aged over 19 years (born before 1987, beginning from 1968);
adults aged over 19 years (born in 1987 or later);in utero cohort (born from April 27 to December 31, 1986).

Population in the Registry (i.e., population size for which cases are registered) is growing
from year to year: while for the first year of study (1986) it was slightly less than 14 million
people, in 2010 it includes over 26 million subjects.
The demographic base of the Registry by attained age and ratio between exposed andunexposed subjects varies from year to year. The proportion of children and adolescents ismonotonically decreasing (only that of born after Chernobyl remain practically unchanged),
while the proportion of adults in the Registry is increasing (including those born both
before and after Chernobyl).
The demographic base of the Registry allows assessing:•• annual dynamics of the age group from 0 to 14 years (born before and after Chernobyl
separately);•• annual dynamics of the age group from 15 to 18 years (born before and after Chernobyl
separately);•• annual dynamics of the age group over 19 years who were aged from 0 to 18 years at
the time of the accident or born after Chernobyl;•• annual dynamics in the in utero cohort.
42

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Since the size of groups in each region and in the whole of Ukraine is known, it is possible
to make arbitrary combinations of regions and to compare the indices for the regions with
the Ukraine as a whole.
To calculate the incidence, the most adequate determination of the number of personyears in a given cohort for a particular year is to use the average population size. It should
be taken into account that we are not dealing with an exact number but with estimatescharacterized by some uncertainty. Some worsening of the quality of demographic
estimates by the end of the study period (1986-2010) could be expected due topostponement of the next census of Ukraine to 2014 or later. A very informative overview
of the problems of quality of demographic data, uncertainties in population parameters,
and possible problems of their interpretation was recently published [35].
Methodology of descriptive analysis of the incidence
Current analysis of thyroid cancer incidence in younger age groups of the populationof Ukraine represents methodologically, in general, a continuation of a series of previous
publications [36-41]. By age at the time of accident and conditions of exposure, the study
subjects are divided into the following three groups:•• exposed as children, aged 0-14 years at the time of accident (0-14 AE);•• exposed as adolescents, aged 15-18 years at the time of accident (15-18 AE);•• exposed in utero, born in May-December 1986 (EIU).
The first group (0-14 AE) is the largest and includes about 11.2 million subjects; thesecond group (15-18 AE) about 2.2 million persons, and the size of the cohort exposed
prenatally is estimated to be about 0.52 million. It should be noted that, according to theconditions of CMR establishment, registered population includes those born beginningfrom December 1, 1968, i.e. actually the second group includes the subjects aged from 15
to <18.32 years at exposure (the population aged 18.32-18.99 belongs to the age cohortborn in 1967).
Subdivision of population into these three groups, besides general medical
considerations, has dosimetric rationale as well. Radiation doses to the thyroid have strong
age dependency [42-46]. Under similar radioecological conditions, the maximal radiationdose is received by the population of younger age. For regional estimates of mean radiationdose [43], the relative exposure dose (normalized to the dose in adults) for children aged
one year is 4.5-6; for children aged 5 years – 3-4; for children aged 10 years – 1.7-2; and forchildren aged 14 – about 1.5.
Similar age relationships are also inherent to risk coefficients (ERRD, EARD) of developing
radiogenic cancer per exposure unit [4,47]. These patterns, taken together, indicate thehighest expected radiogenic effects in the younger age groups of 0-4 years old and 5-9
years old compared with those aged 10 years and older.
Effects of thyroid exposure in utero are markedly different from those of postnatal
irradiation, and information on risks is very limited [4,48,49].
The group born from 1987 was also used in later analyses as a control because it was not
exposed to Chernobyl fallout and therefore does not include Chernobyl radiogenic cancers.
43

Chapter 3

For the analysis by age at diagnosis, cases are subdivided into those diagnosed inchildren (aged 0-14 years at diagnosis), adolescents (aged 15-18 years at diagnosis), andadults (aged ≥19 years at diagnosis). Such subdivision is traditional for oncoepidemiologythat recons childhood cancers a particular category [50,51]. A relatively new trend is toconsider the group of adolescents and young adults (AYA) as patients requiring specific,
tailored diagnostic procedures and streamlined procedures for cancer treatment [51-53].
Current analysis used a partition of 28 regions of Ukraine into two groups according to
the level of thyroid exposure in children and adolescents [44,45, Chapter 2]:•• 6 most contaminated regions (Zhytomyr, Kyiv, Rivne, Chernihiv, Cherkasy regions andKyiv City; average thyroid exposure dose in the group 0-18 years old at the time of theaccident >35 mGy);•• 21 regions with relatively lower levels of contamination (average thyroid exposure dosein the group 0-18 years old <35 mGy).
Childhood and adolescent population of the 6 most contaminated regions accounted
for 19-20% of the total population of corresponding age of Ukraine (Tables 3.1 and 3.2). It
should be stressed that Zhytomyr, Kyiv, and Chernihiv regions are located at a distance up
to 200 km from Chernobyl Nuclear Power Plant; the residents of northern areas of theseregions received the highest thyroid doses [3,54].
Table 3.1
Thyroid cancer cases in selected groups of Ukrainian population in 1986-2010(by periods of diagnosis)

0-14 years at
exposure
6 regions
21 regions
15-18 years at
exposure
6 regions
21 regions
Subjects exposed
in utero
6 regions
21 regions
Subjects born in1987 and later6 regions
21 regions
Total casesaPopulation amillion19861989

19901994

19951999

20002004

20052010

19862010

11.1

59

383

827

1221

2554

5044

2.2
8.9

15
44

191
192

384
443

574
647

1019
1535

2183
2861

2.2

45

162

291

411

733

1642

0.4
1.8

9
36

41
121

89
202

156
255

269
464

564
1078

0.5

0

3

5

26

78

112

0.1
0.4

0
0

1
2

2
3

9
17

32
46

44
68

12.0 b

0

0

11

103

392

506

2.5 b
9.5 b

0
0
104

0
0
548

3
8
1134

32
71
1761

123
269
3757

158
348
7304

- exposed population on 1 January 1987; b - estimation of unexposed population on 1 January 201144

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Table 3.2
Thyroid cancer cases in selected groups of Ukrainian population in 1986-2010(by age at surgery)
Population amillionAged 0-14 years
at surgery

Aged 15-18 years
at surgery

Aged 19+ years
at surgery

0-14 years at
exposure

11.1

453

496

4095

5044

6 regions

2.2

275

244

1664

2183

21 regions

8.9

178

252

2431

2861

15-18 years at
exposure

2.2

-

31

1611

1642

6 regions

0.4

-

5

559

564

21 regions

1.8

-

26

1052

1078

Subjects
exposed in utero

0.5

13

27

72

112

6 regions

0.1

5

11

28

44

21 regions

0.4

8

16

44

68

Subjects born in1987 and later

12.0 b

177

183

146

506

6 regions

2.5 b

57

58

43

158

21 regions

9.5 b

120

125

103

348

643

737

5924

7304

Total
cases
a

Total

- exposed population on 1 January 1987; b - estimation of unexposed population on 1 January 2011

In this work, the period of study is 1986-2010. The annual dynamics of cases and disease
incidence are shown in Tables 3.3 and 3.4, respectively. In the analysis of time trends,
the two-year intervals are used. Also, periods under comparison are subdivided into fiveintervals: 1986-1989 – the period shorter than the minimal duration of latency of radiationinduced thyroid cancer [4,47] when only sporadic thyroid cancers were diagnosed, and four
subsequent intervals (1990-1994, 1995-1999, 2000-2004, 2005-2010) when both sporadic
and radiogenic thyroid cancers are diagnosed in the population.
Analysis of thyroid cancer incidence in 1986-2010 according to the dataof Clinico-morphological Registry
Tables 3.1 and 3.2 summarize data on thyroid cancer in the defined groups, and show
population size in the 6 and 21 regions. Table 3.1 shows the number of cases for the fivestudy periods. Table 3.2 shows the distribution of cases by age at diagnosis, depicting
cancers diagnosed in childhood, adolescence, and adulthood.
Thus, the current analysis involves 6,798 cases in the exposed population, including
45

Chapter 3

5,044 exposed as children, 1,642 cases in irradiated adolescents, and 112 cases of prenatal
exposure. In subjects born after Chernobyl, i.e. in the unexposed population, 506 cases
were diagnosed.
Detailed data on the number of cases, overall incidence for the whole of Ukraine, and forthe 6 contaminated regions and 21 control regions are presented in Tables 3.3-3.7.
Data analysis for the groups by age at exposure takes into account that in every calendar
year we are dealing with a virtual cohort with fixed characteristics of exposure that lived
certain period after exposure. Thus, for a selected population group, over time, from year
to year, the parameters of attained age change (increase) (minimum, maximum, median),as well as does the time after exposure. Attained age significantly affects the sporadic
and radiogenic risks; time elapsed after exposure can also be an important parameter for
calculating radiogenic risk. The attained age and time after exposure uniquely determine
the age at exposure.
Detailed data on thyroid cancer cases and trends in the incidence among those exposed
as children are shown in Table 3.3 and Figure 3.1. During the study period (1986-2010) in
this group, the age varied from 0 to 14 years old in 1986 and from 24 to 38 years old in2010. Table 3.3 shows the cases for the whole of Ukraine, as well as for 6 and 21 regions.
Population size of this group was estimated to be 11.1 million persons at the beginning of
1987. This group showed the maximal number of cases (5,044) with about 43% of these(2,183 cases) registered in the 6 most contaminated regions. A significant increase in theincidence was observed in the first postlatent period (1990-1994) and continued until theend of the study (2010). Ascending trends are common to all four groups represented inFig. 3.1 (males in 6 regions, females in 6 regions, males in 21 regions, females in 21 regions),
although the growth rate and incidences are different for each group. For the low-dose
regions, the increasing incidence is largely determined by the attained age; in the highdose regions, there is an additional influence of radiogenic component and of the factor
of intensive screening. The maximal ​​incidence is expectedly observed in females from
6 contaminated areas (about 15 cases per 100,000 person-years). Incidence rates in themost contaminated areas are significantly higher than those in low-contaminated regions,although their ratio tends to be lower.
Rates in individuals exposed in adolescence are presented in Table 3.4 and Figure 3.2.
The population size of this group was 2.2 million. In 2010, the age of this group reached 3942 years old. The cumulative number of cases is 1,642, of which 564 (34%) were diagnosed
in 6 regions with maximal thyroid doses. The main trends of incidence for males andfemales, in general, are similar to those in exposed during childhood. Due to differencesin median attained age (about 9 years), the absolute values of​​ the incidence for all four
categories (males in 6 regions, females in 6 regions, males in 21 regions, and females in
21 regions) are somewhat higher than the corresponding values in exposed at childhood
age. The incidence in females from 6 most contaminated regions reached 16-18 cases per
100,000 person-years at the end of the study period.
Figure 3.3 demonstrates incidence trends for those exposed at the age from 0 to 18
years old for different periods of study. Areas with the highest incidence (Kyiv, Chernihiv,
Zhytomyr, and Kyiv-City) are located around the Chernobyl Nuclear Power Plant. Of note,46

Epidemiology of thyroid cancer in Ukraine after Chernobyl

there was a pronounced increase in the incidence in this group in low-contaminated regions
during the last time period (2005-2010). Figure 3.4 presents ranked values ​​of cumulative
incidence [55] for those exposed at the age 0-18 years in postlatent period (1990-2010).
High-dose regions, except for Rivne, demonstrate a value above the average for Ukraine.
Also, an increased incidence was noted in Kherson and Vinnitsa regions. It should be
mentioned that a number of studies [56-59] found Polisya (Rivne, Volyn, Zhytomyr regions)
to be an area with low incidence of sporadic thyroid cancer. The contribution of radiogenic
cancers led to the increase in incidence in this region, but the values were found to beslightly below the average for Ukraine (Rivne region) or below the extreme values for Kyiv​​
and Chernihiv regions (Zhytomyr region). The increased incidence in the industrial regionsof Ukraine (Kherson, Dnipropetrovsk, and Zaporizhya regions) was mostly observed in
2000-2010, and does not seem to be associated with radiation factor.
An estimate of the proportion of cases due to radiation among the total number ofcases in the study population is of particular interest. Since thyroid cancers induced byradiation do not have definite markers and cannot be isolated from the whole group, theestimate can only be obtained within a particular statistical model describing the dynamics
of the disease depending on exposure doses (risk assessment model). So, the proportionof radiogenic cancers for the Ukrainian population aged from 0 to 18 years at the time of
accident and for the study period 1990-1997 was estimated to be 30% [56]. A comparative
analysis at the level of regions of the country for the period of 1990-2001 [59] resulted
in an estimate of the proportion of thyroid cancers attributable to Chernobyl radiation of
30% for the whole population of Ukraine and about 50% for the residents of the 3 mostcontaminated areas (Kyiv, Zhytomyr, and Chernihiv regions). Similar analysis performed in
the individual cohort study for the residents (at the time of accident) of the 8 radiationcontaminated areas adjacent to the Chernobyl Nuclear Power Plant, yielded an estimateof excess cancer cases diagnosed during 1998-2000 of about 80% [60], and for the cases
operated in 2001-2007 from 50 to 60% [61].
For individuals exposed in utero, data are presented in Tables 3.1, 3.2, and Figure 3.5.
The population size of this group was estimated to be 0.52 million people. The numberof diagnosed cases is 112. For the purpose of easier interpretation of data, Figure 3.5 also
shows incidence trends for the cohort exposed at the age of 0-4 years old, and for the cohortof unexposed subjects born in 1987-1989 which could be considered a rough estimate ofsporadic thyroid cancer incidence. The in utero group displayed an extremely low incidence
for the period 1990-1999. During 2000-2010, however, the incidence increased sharply andreached values characteristic to the exposed subjects aged 0 to 4 years. If the increase
in incidence in the in utero group was of radiogenic nature, it should be noted that theperiod of latency was substantially longer. Excess incidence for the in utero group waslargely observed in the 6 contaminated regions where 44 cases were diagnosed (39%).
Recently started, a study of radiation effects from in utero exposure is now actively carriedout [48,49] in the framework of prospective observations. Since the number of cases ofthyroid cancer registered in these studies so far is very low (<10), it would be promising toanalyze the risks for this group in well-designed analytical ecologic or case-control studies
using cases from the 6 contaminated areas.
47

48

Cases (F)
Cases (M)Cases (Both)
Incidence
6 regions.
Cases (Both)
21 regions,Cases (Both)
6 regions,
Incidence
21 regions,
Incidence

5

9

1.1

0.5

1

10

0.2

0.6

0.6

0.0

10

0

0.4

0.7

7

3

0.8

1.1

15

5

0.8

1.8

14

8

1.3

1.6

24

7

1.9

2.3

34

10

1.9

2.5

34

11

2.2

4.5

40

20

1.8

2.9

32

13

2.3

3.4

41

15

2.3

5.9

42

26

2.6

3.4

47

15

2.3

5.9

42

26

3.0

7.0

53

31

3.0

7.7

54

34

2.8

7.9

50

35

3.1

6.8

56

30

3.8

9.1

68

40

70

46

83

50

90

44

94

44

3.3

3.9

4.6

5.0

5.2

10.2 10.4 11.3 10.0 10.059451986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 201089
8
6
18 17 23 37 36 54 37 48 59 54 57 70 64 72 79 95 86 95 114 111 106
3
5
2
4
2
5
8
7
9
6
8
8
9
8
11 14 24 137
13 18 21 19 23 32
11 14 10 10 20 22 31 44 45 60 45 56 68 62 68 84 88 85 86 108 104 116 133 134 138
0.5 0.6 0.4 0.4 0.9 1.0 1.4 2.0 2.0 2.7 2.0 2.5 3.0 2.8 3.0 3.8 3.9 3.8 3.9 4.8 4.7 5.2 6.0 6.0 6.2

Table 3.4
Thyroid cancer cases and incidence per 100,000 adolescent population in 1986 (15-18 years old at exposure)1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010Cases (F)47822 29 31 64 59 82 92 108 108 143 170 145 214 213 180 228 241 308 331 386 407 446
Cases (M)434717 16 27 31 27 33 43 33 41 56 39 55 51 52 44 60 65 69 74 72 95
Cases (Both) 8
10 12 29 46 47 91 90 109 125 151 141 184 226 184 269 264 232 272 301 373 400 460 479 541
Incidence
0.1 0.1 0.1 0.3 0.4 0.4 0.8 0.8 1.0 1.1 1.4 1.3 1.7 2.0 1.7 2.4 2.4 2.1 2.5 2.7 3.4 3.6 4.1 4.3 4.9
6 regions,Cases (Both) 303
918 24 49 45 55 61 72 58 85 108 98 131 129 103 113 121 157 165 173 198 205
21 regions,Cases (Both) 510920 28 23 42 45 54 64 79 83 99 118 86 138 135 129 159 180 216 235 287 281 336
6 regions,
Incidence
0.1 0.0 0.1 0.4 0.9 1.1 2.3 2.1 2.6 2.9 3.4 2.8 4.0 5.1 4.7 6.2 6.1 4.9 5.4 5.8 7.5 7.9 8.2 9.4 9.8
21 regions,
Incidence
0.1 0.1 0.1 0.2 0.3 0.3 0.5 0.5 0.6 0.7 0.9 0.9 1.1 1.3 1.0 1.5 1.5 1.4 1.8 2.0 2.4 2.6 3.2 3.1 3.7

Table 3.3
Thyroid cancer cases and incidence per 100,000 childhood population in 1986 (0-14 years old at exposure)

Chapter 3

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Figure 3.1. Time trends of thyroid cancer incidence in 6 and 21 regions of Ukraine for cohort
aged 0-14 years at exposure. AE – age at exposure; 6R – 6 northern regions; 21R – other 21 regions;
F – female; M – male.

Importantly, the interpretation of the number of cases and incidence in the groups
defined by age at diagnosis (at surgery) should take into account that the compositionof such groups changes from year to year as the cohorts become older. Both the size ofthe population and the proportion of exposed and unexposed subjects in the group arechanging.

Figure 3.2. Time trends of thyroid cancer incidence in 6 and 21 regions of Ukraine for cohort
aged 15-18 years at exposure. AE – age at exposure; 6R – 6 northern regions; 21R – other 21 regions;
F – female; M – male.

49

50

7

0.2

0.1

9

0.0

0.1

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

3

0

Cases (F)
Cases (M)
Cases
(Both)
Incidence
6 regions,cases (Both)
21 regions,cases (Both)
6 regions,
Incidence
21 regions,
Incidence

10
0.1

9
0.1

Cases (F)
Cases (M)
Cases
(Both)
8
Incidence
0.1
6 regions,cases (Both) 3
21 regions,cases (Both) 5
6 regions,
incidence
0.1
21 regions,
0.1
Incidence

-

-

-

-

-

-

0.1

0.2

7

4

11
0.1

-

-

-

-

-

-

0.3

0.7

18

12

30
0.4

-

-

-

-

-

-

0.1

1.0

8

15

23
0.3

-

-

-

-

-

-

0.3

2.8

17

37

54
0.8

3.0

19

31

50
1.0

3.8

15

34

49
1.1

4.9

18

37

55
1.4

4.1

11

25

36
1.2

5.7

16

26

42
1.8

4.6

9

14

23
1.5

4.6

9

7

16
2.1

2.0

1

1

2
0.7

-

-

-

-

-

-

-

-

-

-

-

2

-

0.02 0.04

-

1

-

-

0.08

-

1

0.04

-

2

-

1
2
1
2
0.02 0.03 0.02 0.03

0.1

0.1

3

2

5
0.1

0.2

0.1

11

2

13
0.2

0.1

0.4

9

6

15
0.2

0.4 0.4 0.6 0.4 0.9 0.7 1.5 0.5
Born in 1987 and in subsequent years
1
0
1
1
2
10
8
0
2
0
1
3
3
7

0.3

2.6

17

31

48
0.8

0.2

0.7

14

11

25
0.3

19
6

-

-

-

0.1

0.2

6

3

9
0.1

7
2

-

-

-

0.1

0.1

7

2

9
0.1

6
3

-

-

-

0.3

0.3

17

4

21
0.3

18
3

-

-

-

0.1

0.2

5

3

8
0.1

7
1

-

-

-

0.2

0.4

12

5

17
0.3

14
3

-

-

-

0.2

0.2

8

2

10
0.2

8
2

-

-

-

0.2

0.5

9

7

16
0.2

11
5

-

-

-

0.3

0.7

14

9

23
0.4

18
5

-

-

-

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Born before 1987
4
7
7
7
17 15 35 28 30 35 35 29 31 15 10
0
4
2
3
4
13
8
19 20 20 14 20
7
11
8
6
2
-

Table 3.5
Thyroid cancer cases and incidence per 100,000 childhood population (0-14 years old at surgery:born before 1987, and in 1987 and later)

Chapter 3

Cases (F)Cases (M)Cases (Both)
Incidence
6 regions,cases (Both)
21 regions.
cases (Both)
6 regions,
incidence
21 regions,
incidence

Cases (F)
Cases (M)Cases (Both)
Incidence
6 regions,cases (Both)
21 regions,cases (Both)
6 regions,
incidence
21 regions,
incidence

-

-

-

-

-

-

-

0.4

0.5

-

0.7

0.2

-

9

10

-

4

1

-

-

-

-

-

0.3

0.0

8

0

-

-

-

-

-

0.6

0.9

15

5

-

-

-

-

-

0.4

1.0

9

6

-

-

-

-

-

0.6

1.2

13

7

-

-

-

-

-

0.7

1.2

17

7

3.3

11

19

1.4

20

8

2.6

23

15

2.1

11

12

3.1

24

18

4.8

31

29

4.9

10

30

5.2

21

32

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

0.5 0.9 1.0 0.5 1.0 1.3 0.4 0.9
Born in 1987 and in subsequent years
-

0.6

1.6

13

9

0.5

0.7

3

1

1
3
4
0.5

0.8

6.29

19

29

0.6

1.3

7

4

11
0
11
0.7

1.1

6.5

14

20

0.8

0.7

14

3

11
6
17
1.0

2.1

3.3

13

5

1.1

1.7

22

9

28
3
31
1.4

1.4

8.2

3

4

0.9

1.7

19

9

21
7
28
1.1

-

-

-

-

0.7

1.4

14

7

20
1
21
0.8

-

-

-

-

0.8

1.0

16

5

17
4
21
0.9

-

-

-

-

0.8

2.9

15

13

22
6
28
1.3

-

-

-

-

0.9

1.6

15

7

15
7
22
1.1

-

-

-

-

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Born before 1987
8
7
6
17 11 14 20 14 23
20 27 15 25 43 29 36 32 23
13 4
3
6
2
3
4
6
4
8
7
8
11 8
17 17 11 17 16 11 5
3
11 13
8
20 15 20 24 22 30 28 38 23 42 60 40 53 48 34 18
7
0.4 0.5 0.3 0.7 0.5 0.7 0.8 0.8 1.0 1.0 1.3 0.8 1.4 2.0 1.3 1.7 2.1 2.2 2.3 2.8-

Table 3.6
Thyroid cancer cases and incidence per 100,000 adolescent population (15-18 years old at surgery:born before 1987, and in 1987 and later)

Epidemiology of thyroid cancer in Ukraine after Chernobyl

51

Chapter 3

Figure 3.3. Region (oblast) specific time trends of thyroid cancer incidence in the cohort aged
0-18 years at exposure, both sexes.

Table 3.5 and Figure 3.6 demonstrate the statistics of cases and incidence trends forthe age group 0-14 years at diagnosis. The incidence in this group was approximately 0.1
case per 100,000 person-years of childhood population during the period of latency (19861989), and then displayed a sharp increase already noticeable in the early postlatent period(1990-1992). Incidence in females from the 6 most contaminated regions increased in 19921998 more than 20-fold as compared to the period of latency. The increased incidence infemales and males from the 6 regions started to decline synchronously after 1998, withtransition of the most exposed group (aged 0-4 years at the time of the accident) to older
age categories.
Since 2001, this group does not include exposed subjects (even those potentially
irradiated in utero) any more. Incidences in males from the 6 and 21 regions are notsignificantly different, while that in females from the 6 most contaminated regions isapproximately 2-fold higher than in less contaminated regions. Incidence rate for the groupaged 0-14 years is widely used in cancer statistics, and the observed values (0.2-0.4 cases
per 100,000 person-years) for unexposed Ukrainian population can be compared with datafrom other countries and other registries. Such a comparison with the ranked data from 28
European countries [11] suggests that the incidence in Ukraine for the group 0-14 years in
the period 2003-2010 was about the European average.
52

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Figure 3.4. Ranking plot of region (oblast) specific cumulative incidence x 100 000 in 1990-2010
for the cohort aged 0-18 years at exposure, both sexes.

In the age group of 15-18 years old at diagnosis, the increasing incidence in the 6 highdose regions was more gradual compared to the childhood group and reached maximal
values ​​both in females and males in 1998-2002 (Table 3.6 and Figure 3.7). Exposed
population was not in the group since 2006, after which the incidence in males and females
in the 6 and 21 regions became closer.
In the age group of 19+ years old at diagnosis, incidence trends were markedly different
from the younger groups (Figure 3.8). This group has no upper age limit, and its size, medianage, and age structure change every year. Incidence rates in the four categories (males in
6 regions, females in 6 regions, males in 21 regions, females in 21 regions) show increasing
trends. The maximal rates were observed in females from the 6 most contaminated regions,followed by that in females from 21 regions, then in males from the 6 regions and theminimal was in males from 21 regions. It should be noted that in the “adult cohort”, theexposed and unexposed populations are “mixed” beginning from 2006 (Table 3.7).
53

54

Cases (F)
Cases (M)
Cases
(Both)
Incidence
6 regions,cases (Both)
21 regions,cases (Both)
6 regions,
incidence
21 regions,
incidence

6 regions,cases (Both)
21 regions,cases (Both)
6 regions,
incidence
21 regions,
incidence

Cases (F)
Cases (M)
Cases
(Both)
Incidence

-

-

-

-

-

-

-

-

-

-

-

-

0.4

-

-

1.5

-

-

1

-

0.6

-

1

2

0

-

2
0

0
0

-

-

-

-

-

-

-

0.5

-

4

0

0.4

4

3
1

-

-

-

-

-

-

-

0.4

0.9

5

3

0.5

8

4
4

-

-

-

-

-

-

-

0.9

1.1

16

5

0.9

21

19
2

-

-

-

-

-

-

-

0.7

1.6

16

10

0.8

26

19
7

-

-

-

-

-

-

-

1.0

1.7

32

13

1.2

45

33
12

-

-

-

-

-

-

-

1.4

1.6

51

15

1.4

66

54
12

83
21

113 148 166 165 253 246 233 300 338 400 431 511 531 570
26 22 40 34 53 59 54 50 73 85 92 96 100 131

1.4

3.2

69

39

1.8

1.3

2.4

71

33

1.5
68

2.1
80

2.3
88

2.1

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

2.7

2.4

2.8

3.0

3.7

3.9

4.5

4.7

5.2

133 134 119 141 161 208 213 229 249 256

2.9

1.7

2.5
1.6

4.1
1.8

4.5
1.4

4.5
2.1

6.4

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

1.9

6.0

-

-

-

-

-

-

-

1.8

5.0

-

-

-

-

-

-

-

2.1

5.5

-

-

-

-

-

-

-

2.4

6.0

0.5

1.5

4

3

0.7

7

6
1

2.6

7.8

0.5

0.6

7

2

0.5

9

7
2

2.9

8.0

0.9

1.9

16

9

1.1

25

20
5

3.5

8.5

1.4

2.4

32

14

1.6

46

38
8

3.6

9.2

1.6

2.1

44

15

1.7

59

49
10

4.1

9.5

102 102 126 111 173 171 168 209 250 277 310 378 382 445

37

1.9

108 104 139 170 206 199 306 305 287 350 411 485 523 607 631 701

91
17

Born in 1987 and in subsequent years

1.4

1.5

58

16

1.5

74

65
9

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Born before 1987

Table 3.7
Thyroid cancer cases and incidence per 100,000 in subjects aged 19+ years at surgery (born before and after Chernobyl)

Chapter 3

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Figure 3.5. Thyroid cancer incidence in 3 birth cohorts, both sexes: aged 0-4 years at exposure(ATA – age at exposure; B – both sexes); exposed in utero (EIU – exposed in utero, Ukraine – whole
Ukraine, B – both sexes); born in 1987-1989 (BY – year of birthday; Ukraine – whole Ukraine, B – both
sexes).

Figure 3.6. Time trends of thyroid cancer incidence among children aged 0-14 years at surgery.
AS – age at surgery; 6R – 6 northern regions of Ukraine; 21R – other 21 regions of Ukraine; F – female;M – male.

55

Chapter 3

Figure 3.7. Time trends of thyroid cancer incidence among adolescents aged 15-18 years atsurgery. AS – age at surgery; 6R – 6 northern regions of Ukraine; 21R – other 21 regions of Ukraine;F – female; M – male.

Figure 3.8. Time trends of thyroid cancer incidence among adults aged 19+ years at surgery. AS– age at surgery; 6R – 6 northern regions of Ukraine; 21R – other 21 regions of Ukraine; F – female;M – male.

56

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Figure 3.9. Time trends of thyroid cancer incidence in 21 less contaminated regions of Ukraine
among 3 exposed and 1 unexposed birth cohorts. AE – age at exposure; 6R - 6 northern regions of
Ukraine; B – both sexes; BY – year of birthday; Ukraine – whole Ukraine.

As the next step, we consider in a descriptive analysis the birth cohort effect for exposed
and unexposed populations by comparing the incidence trends in the three exposedcohorts (0-4, 5-9, and 10-14 years old at the time of exposure), and in the unexposed cohort(nearest by age to the exposed cohorts) born in 1987-1989. Time trends are consideredseparately for the 6 regions and 21 regions without subdivision by sex. The size of cohorts(0-4, 5-9, and 10-14 years old at exposure) were 0.75, 0.71 and 0.73 million for high-dose
regions, respectively, and about 3 million in each age group for the 21 low-dose regions.
The size of the unexposed cohort born in 1987-1989 for the whole of Ukraine was about
2.2 million.
Figure 3.9 presents incidence trends in the postlatent period for these four cohorts inthe 21 low-dose regions. At the beginning of the study period (1990-1992), the incidence
in each cohort did not exceed 0.5 case per 100,000 person-years. In subsequent years, thecohorts showed a gradual growth of incidence, and at the end of the study incidence rates
ranged from 2.2 to 4.1 cases per 100,000 person-years. It is noteworthy that during theanalyzed period of time the incidences displayed a strictly ordered character according
to attained age. For each fixed period, the cohort born in 1987-1989 showed the lowest
incidence; the next higher value of incidence was observed in the cohort aged 0-4 years at
exposure (the difference in the attained age with the previous cohort was about 4 years);
then in the cohort aged 5-9 years at exposure, and the maximal value was in the cohortof 10-14 years at exposure. The shapes of trends for all cohorts are similar and close to the
exponential curves.
Figure 3.10 presents incidence trends in postlatent period for similar four cohorts in the
6 high-dose regions. The trend in the cohort of subjects born in 1987-1989 is the same as inFig. 3.9, and exponentially increases from 0 to 2.2 cases per 100,000 person-years.
57

Chapter 3

Figure 3.10. Time trends of thyroid cancer incidence in 6 northern regions of Ukraine among 3
exposed, and 1 unexposed birth cohorts. AE – age at exposure; 6R - 6 northern regions of Ukraine;B – both sexes; BY – birtnday year; Ukraine – whole Ukraine.

In the exposed cohorts, the sporadic incidence is supplemented by the radiogenic
component and possibly by the factor of screening [58,62]. The trends in the exposedcohort are less “smooth”, the values vary within the wide range ​​(from 1 to 10.5 cases per
100,000 person-years) and do not show the “natural” ordering by attained age. Moreover, inthe period of 1990-1998, the highest incidence was observed in the youngest cohort of 0-4
years old at exposure, which had accumulated maximal thyroid doses. From 1998 to 2006,
the incidence in this cohort was almost stable: about 5 cases per 100,000 person-years,
after which it continued to increase.
In the cohort aged 5-9 years old at exposure the incidence began to grow as rapidly
as in the younger cohort in 1990, but until 2004 it was lower. The incidence in the older
age group (10-14 years old at exposure) was slowly increasing until 1996, after which thegrowth accelerated and, beginning from 2000, it occupied a “natural” position with thehighest incidence rate.
At the end of the study period (2010), the rate ratios in the groups of 0-4, 5-9, and 10-14
years old at exposure for 21 regions to the cohort born in 1987-1989 were 1.4, 1.7, and 1.9(Fig. 3.9), respectively. The ratios for the 6 high-dose regions are remarkably higher: 3.3, 4.7,
and 4.8, respectively.

58

Epidemiology of thyroid cancer in Ukraine after Chernobyl

Thyroid cancer incidence at the level of the whole population according to the dataof National Cancer Registry
Finally, we will briefly discuss the incidence and mortality rates for the whole populationof Ukraine in the period 1999-2010 according to the National Cancer Registry data [13].
During this period of time, the number of newly reported cases of thyroid cancer increased
steadily from 2,093 (360 males and 1,733 females) cases in 2001 to 2,869 (508 males and2,361females) in 2010. The annual increase in the incidence was 77.6 cases; it was faster infemales (62.8 cases) compared to 14.8 cases in males. The sex ratio (the ratio of the numberof cases in females to the number of cases in males) was 4.7 on average for the period 20012010 ranging from 4.2 to 5.3.
Figures 3.11 and 3.12 represent the trends of thyroid cancer incidence and mortality,
respectively, due to thyroid cancer for the whole population of Ukraine for the period 19992010 according to the NCR [13]. During this period, the incidence showed an ascending
trend both in females (from 6.5 to about 9 cases per 100,000) and males (from 1.9 to 2.5
cases per 100,000). At the same time, mortality rates vary within the ranges 1-1.2 per
100,000 in females and 0.5-0.6 in 100,000 in males with a tendency to a slow decrease. A
similar relationship between the incidence and mortality is typical for the registries of othercountries [1,8,9]. Such a ratio (declining trend of mortality and increasing incidence) reflects
the fact that the increase in incidence is largely due to the growing number of curable welldifferentiated tumors, and also due to improvements in the quality of diagnosis over time.

Figure 3.11. Age-adjusted incidence rates of thyroid cancer per 100,000 general population of
Ukraine in 2000-2010. Data from ref. [13].

59Chapter 3

Figure 3.12. Age-adjusted mortality rates of thyroid cancer per 100,000 general population of
Ukraine in 2000-2010. Data from ref. [13].

In summary, this chapter demonstrates that among the exposed population of children
and adolescents (aged 0-18 years at the time of accident), there has been a significant
increase in thyroid cancer incidence after the minimal period of latency; this tendency
persists for the period of 20 years (1990-2010). At the same time, incidence rate in the 6
most contaminated regions exceeded that in 21 low-contaminated regions for all postlatent
periods of study. However, in both high- and low-contaminated regions, incidence rate
displays a descending tendency, perhaps indicating a gradual decrease in the contributionof radiation factor in the increased thyroid cancer incidence in the cohort aged 0-18 years
at the time of Chernobyl accident. Among those exposed in utero, a significant growth ofincidence started after 15 years since accident and continued to grow during the further
period.
By age at diagnosis, peak incidences in childhood and adolescent groups were observedin 1995-1997 and 2000-2002, respectively. Since 2002 there are no exposed subjects(including the in utero cohort) in the childhood group and since 2006 in the adolescentgroup. Thus, in these age categories all childhood and adolescent cases of radiogenic
thyroid cancer have been realized. In the corresponding groups of unexposed subjects
aged 0-14 and 15-18 years at the time of diagnosis, thyroid cancer incidence is comparable
to the average rate in European countries.
Incidence of sporadic thyroid cancer markedly increases from the age of 25-30 years old; itmay, therefore, be expected that the proportion of radiogenic cancers in Ukraine will decline,
even in the regions with relatively high levels of radiation exposure. On the other hand, as
shown in a recent study [63], a statistically significant contribution of radioinduced thyroid
cancers developing after acute external irradiation can be observed even 50-60 years after
exposure. This fact justifies the need for continuous monitoring and analysis of the incidenceof thyroid cancer in the population groups exposed as a result of Chernobyl catastrophe.
60

Epidemiology of thyroid cancer in Ukraine after Chernobyl

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64Thyroid cancer pathology in Ukraine after Chernobyl

Chapter

4

T Bogdanova, L Zurnadzhy, VA LiVolsi,
ED Williams, M Ito, M Nakashima,
GA Thomas

Thyroid cancer pathology in Ukraine
after Chernobyl

Two main types of thyroid carcinomas may arise from the cells of follicular epithelium:
papillary and follicular. These two types differ by their structure (though follicles are often
present in papillary carcinomas), molecular-biological characteristics, and clinical behaviour.
Besides, medullary thyroid carcinomas (derived from parafollicular neuroendocrine
С-cells), as well as poorly differentiated and anaplastic carcinomas may occur in thegland. The two latter types of tumors may develop from preexisting well-differentiatedtumors. Nonepithelial tumors developing from lymphoid cells (thyroid lymphoma) or frommesenchymal tissue components (thyroid sarcomas) are also known [1-4].
The following are definitions of the main types of thyroid carcinomas based on the WHO
Histological classification [5]:•• papillary thyroid carcinoma (PTC) is a malignant epitheliаl tumor derived from follicular
cells, with characteristic changes in the nuclei (increased size, “ground glass” clearing,
pseudo-intranuclear inclusions and grooves);•• follicular thyroid carcinoma (FTC) is an encapsulated or partly encapsulated malignant
epitheliаl tumor, derived from follicular cells, with signs of marked invasion into tumor
capsule and/or tumor capsule vessels, without changes in tumor cell nuclei characteristic
for PTC;•• medullary thyroid carcinoma (MTC) is a malignant tumor derived from С-cells;•• poorly differentiated thyroid carcinoma (PDTC) is a malignant tumor derived fromfollicular cells, with signs of decreased differentiation and being an intermediary
between well-differentiated (PTC and FTC) and undifferentiated (anaplastic) thyroid
carcinoma, both by histological structure, aggressiveness and clinical behaviour;•• anaplastic (undifferentiated) thyroid carcinoma (ATC) is the most malignant epitheliаlthyroid tumor derived from follicular cells, partly or completely consisting ofundifferentiated cells.
According to the above-mentioned classification, the present chapter describes
and analyses the main types of thyroid carcinomas which were detected in the group65

Chapter 4
at increased risk for development of radiation-induced thyroid cancer in the period of asignificant rise in its incidence after Chernobyl: 1990-2010 (see Chapter 3). A total of 2,960
cases diagnosed in children and adolescents of Ukraine (aged 0 to 18 years at the time of
the Chernobyl accident) as well as in those who were born after the accident are reviewed(Table 4.1).
Morphological characteristics of 2,658 thyroid carcinomas in individuals born before
Chernobyl are considered for three age groups: children operated on at the age from 4
to 14 years old, adolescents operated on at the age from 15 to 18 years old, and adults
operated on at the age from 19 to 42 years old. Also, a comparative analysis of morphologicalchanges is carried out for four time periods: 1990-1994, 1995-1999, 2000-2004, and 20052010 (Table 4.2). Overall, 287 thyroid cancers in children (out of 453 detected in Ukraine,
63.4%), 244 carcinomas in adolescents (out of 527 detected in Ukraine, 46.3%), and 2,127
carcinomas in adults (out of 5,706 detected in Ukraine, 37.3%) were studied for the period
1990-2010. Practically all cancers in children and adolescents included in the analysis havebeen additionally verified by the international experts, Professors VA LiVolsi and ED Williams,
in the framework of joint international projects. Furthermore, 1,512 thyroid carcinomas
in children, adolescents and adults operated in 1998-2010 included in the international
Chernobyl Tissue Bank have been additionally verified by a Panel of experts-pathologistsof the Project (see Chapter 6). It should be noted that since 2001, children born before
Chernobyl were no longer registered because they naturally moved over to the age groupof “adolescents” who, in turn, moved to the group of “adults” beginning from 2005.
Table 4.1
Total number of thyroid cancer cases under study

Type
PTC
FTC
MTC
PDTC
Total

Born before Chernobyl
number
%
2478
93.2
137
5.1
39
1.5
4
0.2
2658
100
2960

number
264
32
6
302

Born after Chernobyl
%
87.4
10.6
2.0
100

PTC – papillary thyroid carcinoma; FTC – follicular thyroid carcinoma; MTC – medullary thyroid carcinoma;
PDTC – poorly differentiated thyroid carcinoma

As shown in Table 4.2, among all cancers, papillary thyroid carcinoma was mostprevalent, and accounted for more than 90% of cases in all age groups and for all time
periods. This fully corresponds to the previously obtained numerous data published byscientists from Ukraine, Belarus, and Russian Federation [6-15], and to the findings of joint
scientific projects carried out in cooperation between the affected countries and leading
research centres of the world [16-25].
It has been established that PTC was the most common malignant thyroid tumor not
only after internal radiation exposure, but also after external exposure of head and neck66

Thyroid cancer pathology in Ukraine after Chernobyl
area, especially in childhood [1-4,26-30]. Thyroid cancers that had been detected after
Hiroshima and Nagasaki A-bombings [31-35] or the hydrogen bomb test in the MarshallIslands were also mainly PTCs [36].
Table 4.2
Number of thyroid cancer cases in patients born before Chernobyl
Children aged up to 14 years at surgery
2005-2010

1990-2010Type

number1990-1994%

number

1995-1999%

number2000-2004%

number %number %

PTC

127

97.0

135

93.1

10

90.1

-

-

272

94.8

FTC

2

1.5

6

4.1

-

-

-

-

8

2.8

MTC

2

1.5

4

2.8

1

0.9

-

-

7

2.4

PDTC

-

-

-

-

-

-

-

-

-

Total

131

100

145

100

11

-

-

287

100

100

Adolescents aged from 15 to 18 years at surgery
1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

number%number%number%number %number %

PTC

27

96.4

81

92.0

117

91.4

-

-

225

92.2

FTC

1

3.6

7

8.0

10

7.8

-

-

18

7.4

MTC

-

-

-

-

1

0.8

-

-

1

0.4

PDTC

-

-

-

-

-

-

-

-

-

-

Total

28

100

88

100

128

100

-

-

244

100

Adults aged from 19 to 42 years at surgery
1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

number%number%number%number %number %

PTC

13

92.9

149

96.8

605

91.5

1214

93.5

1981

93.1

FTC

1

7.1

4

2.6

45

6.8

61

4.7

111

5.2

MTC

-

-

1

0.6

10

1.5

20

1.6

31

1.5

PDTC

-

-

-

-

1

0.2

3

0.2

4

0.2

Total

14

100

154

100

661

100

1298

100

2127

100

All age groups
1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

number%number%number%number %number %

PTC

167

96.5

365

94.3

732

91.5

1214

93.5

2478

93.2

FTC

4

2.3

17

4.4

55

6.9

61

4.7

137

5.1

MTC

2

1.2

5

1.3

12

1.5

20

1.6

39

1.5

PDTC

-

-

-

-

1

0.1

3

0.2

4

0.2

Total

173

100

387

100

800

100

1298

100

2658

100

67

Chapter 4
PTCs in Ukrainian patients varied in size from 0.3 to 75 mm. The analysis shows that theprevalence of tumors sized up to 10 mm (Table 4.3) - when combining all time periods was increasing significantly and succesively in the age series: children (10/272, 3.7%) –adolescents (27/225, 12.0%) – adults (458/1981, 24.2%), p=0.0001 (here and hereafter, theChi-square test for trend or Fisher’s Exact text are used for comparison of subgroups).
A significant ascending linear trend (р=0.0001) in the frequency of “small” PTCs was also
noted for the combined age groups in time elapsed after Chernobyl, i.e. by time periods:
1990-1994 (5/167, 3.0%) – 1995-1999 – (21/365, 5.7%) – 2000-2004 (95/732, 13.0%) – 2005-2010 (374/1214, 30.8%). An inverse linear relationship was observed in the analysis of thefrequency of carcinomas sized more than 40 mm (Table 4.3). The frequency was decreasing
gradually and significantly (р=0.0001) both in age series: children (57 out of 272 cases, 20.9%) –adolescents (23 out of 225 cases, 10.2%) – adults (181 out of 1981 cases, 9.1%),
and by time periods: 1990-1994 (33/167, 19.8%) – 1995-1999 (60/365, 16.5%) –2000-2004 (70/732, 9.5%) – 2005-2010 (98/1214, 8.1%).
Analysis of small encapsulated tumors versus non-encapsulated or partly encapsulated
did not reveal significant differences in age or time series. By contrast, significant ascending
linear age and time trends (р=0.0001) were found for fully encapsulated large tumors(sized more than 40 mm): children (3 out of 57 cases, 5.3%) – adolescents (5 out of 23 cases,
21.7%) – adults (84 out of 181 cases, 46.4%); 1990-1994 (1/33, 3.0%) – 1995-1999 (8/60,
13.3%) – 2000-2004 (26/70, 37.1%) – 2005-2010 (56/98, 57.1%).
For the combined encapsulated tumors of any size, significant ascending linear trends
were also noted (р=0.0001): children (21 out of 272 cases, 7.7%) – adolescents (35 out of
225 cases, 15.6%) – adults (582 out of 1981 cases, 29.4%); 1990-1994 (9/149, 6.0%) – 19951999 (91/365, 24.9%) – 2000-2004 (172/732, 23.5%) – 2005-2010 (363/1214, 29.9%).
PTC is generally known to display varying histological structures and therefore it is further
subdivided into subtypes or variants. According to the WHO Histological classification,these variants include classic papillary, follicular, macrofollicular, solid, oxyphilic-cell,
clear-cell, diffuse-sclerosing, tall-cell, columnar-cell, cribriform-morular, and Warthin-likevariants. Papillary microcarcinoma is also considered to be a separate variant [5].
With regard to the classic papillary variant, at least 80% of tumors featured typical
papillary formations with characteristic fibrovascular core and optically clear (“groundglass”) nuclei (Fig. 4.1 A) containing intranuclear grooves and pseudo-cytoplasmic
inclusions. Most of the tumor cells showed positive immunohistochemical staining withantithyroglobulin antibodies (Fig. 4.1 B).
In the follicular variant of PTC, typical papillary structures are scarce or absent (Fig.
4.2 A). Cleared nuclei with chromatin localized at the periphery is the main distinctive
feature of this subtype. Positive immunohistochemical reaction with antithyroglobulin
antibodies, similarly to the classic papillary variant, was observed in most tumor cells(Fig. 4.2 B).
In the solid variant of papillary thyroid carcinoma, tumors with alveolar-solid growth
pattern were most prevalent (Fig. 4.3 A). Areas with solid-trabecular structures wereoccasionally observed (Fig. 4.3 B). Papillary structures were generally absent, but smallfollicular areas could occur. The fact that tumors of this subtype are PTCs is substantiatedby the structure of tumor cell nuclei. Intranuclear grooves and nuclear pseudoinclusions
were best seen on electron microscopy (Fig. 4.3 D, E). Thyroglobulin in tumor cells, unlike inthe classic papillary and follicular variants, was detected only focally (Fig. 4.3 C).
68

Thyroid cancer pathology in Ukraine after Chernobyl
Table 4.3
Size of papillary thyroid carcinomas in patients born before Chernobyl
Children aged up to 14 years at surgery
Size, mm1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

number%number %number%number %number %up to 5

1

0.8

-

-

-

-

-

-

1

0.4

6-10

2

1.6

7

5.2

-

-

-

-

9

3.3

11-20

41

32.3

71

52.6

3

30.0

-

-

115

42.3

21-30

41

32.3

17

12.6

5

50.0

-

-

63

23.2

31-40

15

11.8

10

7.4

2

20.0

-

-

27

9.9

41-50

15

11.8

18

13.4

-

-

-

-

33

12.1

51-60

9

7.0

6

4.4

-

-

-

-

15

5.5

> 60

3

2.4

6

4.4

-

-

-

-

9

3.3

Total

127

100

135

100

10

100

-

-

272

100

Adolescents aged from 15 to 18 years at surgery
1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

number%number %number%number %number %up to 5

-

-

-

-

6

5.1

-

-

6

2.7

6-10

1

3.7

7

8.6

13

11.1

-

-

21

9.3

11-20

10

37.0

38

46.9

51

43.6

-

-

99

44.0

21-30

7

25.9

19

23.5

28

23.9

-

-

54

24.0

31-40

5

18.6

7

8.7

10

8.6

-

-

22

9.8

41-50

1

3.7

6

7.4

8

6.8

-

-

15

6.7

51-60

-

-

3

3.7

-

-

-

-

3

1.3

>60

3

11.1

1

1.2

1

0.9

-

-

5

2.2

Total

27

100

81

100

117

100

-

-

225

100

Adults aged from 19 to 42 years at surgery
1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

number%number %number%number %number %up to 5

-

-

-

-

20

3.3

98

8.1

118

6.0

6-10

1

7.7

7

4.7

56

9.3

276

22.7

340

17.2

11-20

3

23.0

67

43.0

289

47.8

439

36.2

798

40.3

21-30

5

38.5

45

30.2

130

21.5

215

17.7

395

19.9

31-40

2

15.4

10

6.7

49

8.1

88

7.2

149

7.5

41-50

1

7.7

12

8.0

33

5.4

53

4.4

99

5.0

51-60

1

7.7

3

2.0

20

3.3

28

2.3

52

2.6

>60

-

-

5

3.4

8

1.3

17

1.4

30

1.5

Total

13

100

149

100

605

100

1214

100

1981

100

69

Chapter 4

Continuation of Table 4.3

up to 5
6-10
11-20
21-30
31-40
41-50
51-60
>60
Total

1990-1994
number %
1
0.6
4
2.4
54
32.3
53
31.7
22
13.2
17
10.2
10
6.0
6
3.6
167
100

1995-1999
number %
21
5.7
176
48.2
81
22.2
27
7.4
36
9.9
12
3.3
12
3.3
365
100

All age groups
2000-2004
number
%
26
3.6
69
9.4
343
46.9
163
22.3
61
8.3
41
5.6
20
2.7
9
1.2
732
100

2005-2010
number %
98
8.1
276
22.7
439
36.2
215
17.7
88
7.2
53
4.4
28
2.3
17
1.4
1214
100

1990-2010
number %
125
5.0
370
14.9
1012
40.8
512
20.6
198
8.0
147
5.9
70
2.8
44
1.8
2478
100

Figure 4.1. Classic papillary carcinoma. (A) Typical papillary structures with well-developed
fibrovascular core and cleared tumor cell nuclei. Haematoxylin and eosin, original magnification
x100. (B) Strong diffuse cytoplasmic immunostaining for thyroglobulin, original magnification x200.

These three subtypes accounted for more than 50% of all PTCs under study for all age
groups and all periods of time (Table 4.4).
Of note, PTCs were not always monomorphic histologically which is a difficulty whenascribing tumors to one of the three main variants. In many cases tumors had a mixed
growth pattern (herein referred to as “mixed variant”) (Fig. 4.4), comprising a combinationof papillary, follicular or solid components (Table 4.5).
Diffuse sclerosing variant was rather rare, 8.7% cases in children in the first period of time
(Table 4.4). The frequency of this variant was significantly decreasing (р=0.0001) both inage and time series (Table. 4.4). Tumors with this structure were characterized by:•• diffuse extension of tumoral foci throughout the thyroid•• fibrous-sclerotic changes•• marked thyroiditis•• abundance of psammoma bodies•• foci of squamous-cell metaplasia.

70

Thyroid cancer pathology in Ukraine after Chernobyl

Figure 4.2. Follicular variant of papillary thyroid carcinoma. (A) Diffuse nuclear features ofpapillary carcinoma. Haematoxylin and eosin, original magnification x100. (B) Strong diffuse
cytoplasmic immunostaining for thyroglobulin, original magnification x100.

Figure 4.3. Solid variant of papillary thyroid carcinoma. (A) Alveolar-solid growth pattern.
Haematoxylin and eosin, original magnification x100. (B) Trabecular growth pattern. Haematoxylin
and eosin, original magnification x100. (C) Focal immunostaining for thyroglobulin, original
magnification x50. (D) Intranuclear inclusions on electron microscopy, original magnification x5,000.
(E) Nuclear grooves on electron microscopy, original magnification x7,000.

71

Chapter 4Tumoral foci had generally solid or papillary-solid structure. A marked invasion of tumor
tissue and psammoma bodies to lymphatic vessels was characteristic (Fig. 4.5).

Figure 4.4. Mixed variant of papillary thyroid carcinoma. (A) Papillary-follicular growth pattern.
Haematoxylin and eosin, original magnification x100. (B) Papillary-solid growth pattern. Haematoxylin
and eosin, original magnification x50. (C) Solid-follicular growth pattern. Haematoxylin and eosin,
original magnification x100.

Figure 4.5. Diffuse sclerosing variant of papillary thyroid carcinoma. (A) Diffuse tumor growth,numerous psammoma bodies, marked fibrosis, lymphocytic infiltration. Haematoxylin and eosin,
original magnification x20. (B) Tumor aggregates inside lymphatic vessels. Haematoxylin andeosin, original magnification x100. (C) Squamous-cell metaplasia. Haematoxylin and eosin, original
magnification x200.

72

Thyroid cancer pathology in Ukraine after Chernobyl
Table 4.4
Subtypes of papillary thyroid carcinomas in patients born before Chernobyl
Children aged up to 14 years at surgery
1995-1999
2000-2004
2005-2010
1990-2010
Subtypenumber %number %number %number %PV
1914.1 220.0 3011.0
FV
1712.6 220.0 65
23.9
SV
17
12.6 220.0 57
21.0
Mixed V76
56.3 440.0 103
37.9
DSV
6
4.4
17
6.2
Warthin
Cribriform
Total
135
100 10100 272
Adolescents aged from 15 to 18 years at surgery
1990-1994
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %number %PV
4
14.8 2125.9 23
19.6 4821.3
37.0 1316.0 24
20.5 47
20.9
FV
10
SV
5
18.5 810.0 119.4
24
10.7
Mixed V8
29.7 3543.2 58
49.6 101
44.9
DSV
4
4.9
4
1.8
Warthin
1
0.9
10.4
Cribriform Total
27
100 81
100 117100 225
Adults aged from 19 to 42 years at surgery
1990-1994
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %number %PV
2
15.4 5436.2 223
36.9 388
32.0 667
33.7
FV6
46.1 30
20.1 10216.9 19416.0 332
16.8
SV2
15.4 12
8.1
25
4.1
79
6.5
118
5.9
42.3
Mixed V3
23.1 5134.3 242
40.0 541
44.6 837
DSV
2
1.3
2
0.3
2
0.1
6
0.3
Warthin
11
1.8
8
0.7
19
0.9
Cribriform 2
0.1
2
0.1
Total
13
100 149
100 605
100 1214
100 1981
100
All age groups
1990-1994
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %number %
PV
15
9.0
94
25.8 248
33.9 388
32.0 74530.0
FV
6237.1 60
16.4 12817.5 19416.0 44417.9
SV4526.9 37
10.1 38
5.2
79
6.5
199
8.1
Mixed V34
20.4 162
44.4 304
41.5 541
44.6 1041
42.0
DSV
11
6.6
12
3.3
2
0.3
2
0.1
27
1.1
Warthin
12
1.6
8
0.7
20
0.8
2
0.1
2
0.1
Cribriform Total
167
100 365
100 732
100 1214
100 2478100
PV – classic papillary variant; FV – follicular variant; SV – solid variant; Mixed V – mixed variant;
DSV – diffuse sclerosing variant; Warthin – Warthin-like variant; Cribriform – cribriform-morular variant
1990-1994
Number %
9
7.1
46
36.2
38
29.9
23
18.1
11
8.7
127
100

73

Chapter 4
Table 4.5
Structural components of mixed variant of papillary thyroid carcinoma in patientsborn before Chernobyl

Structure
PF
PS
PFS
SF
Total

1990-1994
Number %
3
13.0
4
17.4
2
8.7
14
60.9
23

PF
PS
PFS
SF
Total

1990-1994
Number %
1
12.5
7
87.5
8

PF
PS
PFS
SF
Total

1990-1994
Number %
2
75.0
1
25.0
3
100

PF
PS
PFS
SF
Total

1990-1994
Number %
6
17.6
4
11.8
2
5.9
22
64.7
34
100

Children aged up to 14 years at surgery
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %12
15.8 125.0 16
15.5
7
9.2
11
10.7
1
1.3
3
2.9
56
73.7 375.0 7370.9
764
100 103100
Adolescents aged from 15 to 18 years at surgery
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %12
34.9 2543.1 3837.6
720.0 1119.0 18
17.8
5
8.6
5
5.0
16
45.7 1729.3 4039.6
35
100 58100 101100
Adults aged from 19 to 42 years at surgery
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %20
39.2 148
61.2 252
46.6 42250.4
1121.6 32
13.2 100
18.5 143
17.1
5
9.8
10
4.1
34
6.2
49
5.9
15
24.4 52
21.5 155
28.7 223
26.6
51
100 242100 541
100 837100
All age groups
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %44
27.2 174
57.2 252
46.6 476
45.7
2515.4 43
14.1 100
18.5 172
16.5
6
3.7
15
5.0
34
6.2
57
5.5
87
53.7 72
23.7 155
28.7 336
32.3
162
100 304
100 541
100 1041

PF – papillary-follicular variant; PS – papillary-solid variant; PFS – papillary-follicular-solid variant;
SF – solid-follicular variant

According to the literature, the development of PTC with diffuse-sclerosing structure
has been associated with previous radiation exposure [1,2,37,38]. However, studies of«post-Chernobyl» carcinomas did not confirm this notion as such tumors were observed in
not more than in 7.0-9.0% cases and mostly in children [10,11,16].

74

Thyroid cancer pathology in Ukraine after Chernobyl
In less than 1% of cases, the Warthin-like variant (Table 4.4) was found in later periods(2000-2004 and 2005-2010, mostly in adults). Its distinctive feature is a profoundintratumoral thyroiditis (Fig. 4.6). Tumors were represented by oxyphilic cells and generally
had papillary or papillary-solid structure; they were also characterized by the very strong
diffuse immunohistochemical reaction for thyroglobulin (Fig. 4.6 D) and TTF-1 (Fig. 4.6
E). Referring the Warthin-like variant to PTC is justified by enlarged and cleared nuclei(Fig. 4.6 C). The proliferative activity of tumor cells (immunohistochemical reaction with
anti-Ki67 antibodies) was not high, less than 5% (Fig. 4.6 F), which is, again, characteristicof PTC in general [3,4]. The lesions ranged in size from 5 to 42 mm, all of them were
non-encapsulated. Lymph node metastases were identified in 7 out of 19 cases (36.8%),

Figure 4.6. Warthin-like variant of papillary thyroid carcinoma. (A, B) Papillary-solid andpapillary growth pattern, profound intratumoral thyroiditis. Tumors are represented by oxyphilic
cells. Haematoxylin and eosin, original magnification x100. (C) Nuclear features of Warthin-likevariant. Haematoxylin and eosin, original magnification x200. (D) Strong diffuse cytoplasmic
staining for thyroglobulin, original magnification x100. (E) Strong nuclear reactivity for TTF-1,
original magnification x100. (F) Focal nuclear reactivity for Ki67, original magnification x100.

75

Chapter 4
but none showed distant metastases (Table 4.9). Our data are in agreement with the opinionof other authors [39] that these tumors behave similarly to conventional PTCs. The impact
of radiation on the development of this subtype is not established yet.
In two cases (female patients aged 26 and 27 years), an even more rare variant of PTC,
the Cribriform-morular, was identified (0.1%). Tumors were represented by the nodulelike lesions localized between markedly sclerosed stroma (Fig. 4.7 A, 4.7 B). An essential
difference between this and other subtypes was the presence of numerous morulas (Fig.
4.7 C, 4.7 D). Tumor areas had solid or follicular structure with the colloid being practicallyabsent in all follicles. In the solid areas, cells were of polygonal shape; nuclei were more
dense than in other subtypes and contained a small number of intranuclear inclusions.
Immunohistochemical reaction with antithyroglobulin antibodies was practically negative,
while the reaction with anti-TTF-1 antibodies was highly intensive and diffuse in tumor
cell nuclei but virtually absent in the nuclei of the cells within morulas (Fig. 4.7 E). A
highly intensive reaction to ß-catenin was revealed in the nuclei and cytoplasm of tumor
cells; staining in morulas was rather weak and had a diffuse pattern (Fig. 4.7 F). Nuclei
positive for Ki67 were rare both in tumor and in morular cells (Fig. 4.7 G); weakly positive
for TP53 (p53) nuclei were detected in 3-5% of tumor and morular cells (Fig. 4.7 H). The
described tumors fully correspond to the data available in the literature [3,4] not only bymorphological characteristics, age and gender of patients, but also by the diagnosis offamilial adenomatous polyposis (FAP) in these individuals as stated in their medical records.
No impact of radiation on the development of this subtype of PTC has been found.
The most aggressive variants according to the literature [1,3,4,37,40], the Tall-celland Columnar-cell variants, were not observed among PTCs under study. In three casesin adults (0.3%), only isolated tall-cell areas were noted in the tumors with papillarytrabecular architecture. Columnar-cell areas were detected in an adult patient only in one
tumor (0.1%) which was, again, of papillary-trabecular structure. Such areas demonstrated
pseudostratified columnar cells with subnuclear and supranuclear cytoplasmic vacuoles(Fig. 4.8 A). Thyroglobulin in such areas was expressed at the apical part of cells and in the
narrowed fine intrapapillary space (Fig. 4.8 B); practically all nuclei of tumor cells expressed
TTF-1 (Fig. 4.8 C), and only few (2-3%) expressed Ki67 (Fig. 4.8 D). The reaction with antiTP53 antibodies was negative.
Further, we analyse three main subtypes of PTC (classic papillary, follicular, and solid
variants) and tumors with mixed growth pattern for age and time related changes.
In the first five years of a significant rise in thyroid cancer incidence (1990-1994), PTCs
in children operated at under 15 years of age (127 out of 167 cases, 76.0%) were the mostprevalent. 66.1% of these tumors had follicular and solid structure (Table 4.4). Of note, thefollicular variant differed from that described in adults by more roundish nuclei and thepresence of solid component (up to 20.0%) in all cases, commonly in the areas of intrathyroidal
or extrathyroidal extension. Besides, in the tumors with mixed growth pattern (“mixed
variant”) in this age group (Table 4.5), the prevalence of the solid-follicular architecture wassignificantly higher than those of other structural combinations (p<0.0018 vs papillaryfollicular; p<0.0058 vs papillary-solid, and p<0.0001 vs papillary-follicular-solid).
Such architectural particularities of tumors in children prompted the introduction of
the special solid-follicular “childhood variant” of PTC [38], which combines tumors of solid,
follicular, and solid-follicular variants.

76Thyroid cancer pathology in Ukraine after Chernobyl

Figure 4.7. Cribriform-morular variant of papillary thyroid carcinoma. (A, B) Nodule-like lesions,marked stromal sclerosis. Haematoxylin and eosin, original magnification x10-panoramic; x50. (C,D) Numerous morulas and empty follicles. Haematoxylin and eosin, original magnification x50;
x200. (E) Diffuse strong nuclear reactivity for TTF-1, original magnification x200. (F) Diffuse strong
cytoplasmic and nuclear staining for ß-catenin in tumor cells; diffuse and weakly positive staining inmorulas. Original magnification x200. (G) Focal nuclear reactivity for Ki67 in tumor and morular cells,
original magnification x200. (H) Focal weak nuclear reactivity for TP53 in tumor and morular cells,
original magnification x200.

77

Chapter 4

Figure 4.8. Columnar-cell areas of papillary thyroid carcinoma. (A) Papillary-trabecular growth
pattern, prominent subnuclear vacuoles, and moderate pseudostratification. Haematoxylin andeosin, original magnification x100. (B) Strong apical cytoplasmic thyroglobulin staining, original
magnification x100. (C) Diffuse strong nuclear reactivity for TTF-1, original magnification x100. (D)Focal nuclear reactivity for Ki67, original magnification x100.

During the first decade after Chernobyl, tumors of “childhood variant” accounted for
up to 80% in patients operated at the age under 15 years in Ukraine and Belarus. These
PTCs were characterized by marked intrathyroidal and extrathyroidal extension, invasionof lymphatic and blood vessels, and very frequent regional metastases [11,17,18,20,41,42].
It should be noted that such a “combined” solid-follicular variant of PTC was much moreprevalent among children of Ukraine and Belarus affected by the Chernobyl accident
compared to nonexposed children of England and Wales [11,17].
In addition, it has been established in Ukraine that the relative risk of development of“childhood variant” PTC was increasing with thyroid exposure dose: 2.2-fold at the dose
0.05 to 0.2 Gy, 5.2-fold at 0.2 to 1.0 Gy, and 6.7-fold at >1.0 Gy. Overall, the relative risk ofdevelopment of such tumors at thyroid exposure dose exceeding 0.05 Gy was 3.7 [43].
In children of Russia, the follicular variant of PTC [44] was most common in postChernobyl years. No correlation between morphological structure and thyroid exposure
dose was found [14].
78Thyroid cancer pathology in Ukraine after Chernobyl
It has been claimed that the presence of a marked solid component determined theaggressiveness of biological behaviour of PTC in children [16,17,18,20,38,45,46]. In thiscontext, of interest are data obtained later by a group of experts-pathologists (which also
included representatives of Ukraine, Belarus and Russia) in the framework of an international
project for establishment of the Chernobyl Tissue Bank. The group performed an analysisof the histological structure of PTCs and their latency [47]. Three groups of children havebeen selected differing by age at exposure, age at surgery, and by the period of latency(defined as time interval between the Chernobyl accident and date of surgery). A significant
difference was found in the prevalence of less differentiated (solid) and more differentiated(papillary and follicular) structural components depending on latency. PTCs developing after
a short latency were characterized by the more prominent solid component and by more
pronounced intrathyroidal and extrathyroidal extension as compared to those occurring after
a longer latency. The latter tumors generally displayed papillary-follicular growth pattern andperitumoral fibrosis, which are usually considered to be less aggressive pathological features.
It needs to be emphasized that PTCs with architecturally less differentiated solid areas
should not be erroneously assimilated into the poorly differentiated thyroid tumors group[1,3,4,25,30,37,48] as these are different in both histological structure and prognosis.
The same group of pathologists proposed later that the abundance of the solid
component in “post-Chernobyl” childhood PTCcould also be influenced by a moderate
iodine deficiency observed in the affected countries as compared to England and Wales,and especially to Japan [49].
Since 25 years have already passed after the Chernobyl accident, children who had
experienced the strongest impact of radioactive iodine from fallout have already moved
over to the age category of “adults” for a long time. Therefore, it appears inappropriate tocontinue using the term “childhood variant” today; for this reason, our analysis was based on
generally accepted PTC subtypes. The highest percentage of tumors with a solid structure,
which, as mentioned above, are architecturally less differentiated, was observed in children(21.0%). This is in line with the results of other studes of radiation-induced or sporadic PTC
in children [3,4,25,29,46]. The frequency of tumors with classic papillary structure was, on
the contrary, the highest in adults (33.7%), with a highly significant age trend (р=0.0001).
The ratio of PTC subtypes significantly changed with time after Chernobyl, i.e. withincreasing period of latency. In all age groups the percentage of tumors with solid structure
was gradually decreasing while that of classic papillary and, especially, mixed structure wasincreasing (Table 4.4). Similarly to the age-related changes, time-related linear trends werealso highly significant (р=0.0001). Besides, in all age groups combined, the frequency of thesolid variant decreased from 26.6% in the first period of observation (1990-1994) to 6.5% in
the last period (2005-2010) while the frequency of the classic papillary variant increased from
9.0 to 32.0%. Structural combinations of the mixed variant also markedly changed with time
(Table 4.5). The frequency of tumors with solid-follicular structures gradually decreased (from64.7% in 1990-1994 to 28.7% in 2005-2010), and the percentage of tumors with papillaryfollicular structure increased (from 17.6% в 1990-1994 to 46.6% in 2005-2010).
Invasive features of PTCs under study (extrathyroidal extension to soft tissues adjacentto the thyroid, regional and distant metastases), and their relationship to tumor size andmultifocality as assessed according to the seventh edition of TNM Classification [50], alsochanged significantly with time after Chernobyl (Table 4.6).
79

Chapter 4
Table 4.6
Size of papillary thyroid carcinomas and the prevalence of lymph node and distantmetastases in patients born before Chernobyl
1st period: surgery in 1990-1994
All age groups
N0

N1a

N1b

Total pT

M0

M1

numbernumbernumbernumber %numbernumberpT1a (up to 5 mm) 1

1

0.5

1

pT1a (6-10 mm)

3

1.8

3

23

13.8

23

pT/tumor size3

pT1am (1-5 mm)
pT1am (6-10 mm)
pT1b (11-20 mm)

176

pT1bm (11-20 mm)
pT2 (21-40 mm)

1
23

4

2

29

17.4

28

8

2

2

12

7.2

11

1

pT2m (21-40 mm)
pT3 (>40 mm)*
pT3m (>40 mm)*
pT3 (any size)**

30
11

13

pT3m (any size)**Total

63 (37.7%)

25 (15.0%)

61

85

50.9

55

14

14

8.4

1

13

79 (47.3%)

167

100

122 (73.1%)

45 (26.9%)

2nd period: surgery in 1995-1999
All age groups
pT/tumor size

N0

N1a

N1b

Total pT

M0

M1

numbernumbernumbernumber %numbernumber

16

1

17

4.7

17

70

22

96

26.3

95

3

0.8

3

pT1a (up to 5 mm)
pT1a (6-10 mm)
pT1am (1-5 mm)
pT1am (6-10 mm)
pT1b (11-20 mm)

4

pT1bm (11-20 mm) 3
pT2 (21-40 mm)

28

pT2m (21-40 mm)

214

pT3 (>40 mm)*

10

2

39

34

3
1

45

12.3

45

2

0.5

2

13

3.6

13

1

pT3m (>40 mm)*
pT3 (any size)**
pT3m (any size)**
Total

80

168 (46.0%) 73 (20.0%)

92

165

45.2

115

50

24

24

6.6

3

21

124 (34.0%) 365

100

293 (80.3%) 72 (19.7%)

Thyroid cancer pathology in Ukraine after Chernobyl

3rd period: surgery in 2000-2004
N0
pT/tumor size
numberpT1a (up to 5 mm) 24
pT1a (6-10 mm)
40
pT1am (1-5 mm)
1
pT1am (6-10 mm) 6
pT1b (11-20 mm) 181
pT1bm (11-20 mm)
pT2 (21-40 mm)
75
pT2m (21-40 mm) 7
pT3 (>40 mm)*20
pT3m (>40 mm)* 1
pT3 (any size)**
56
pT3m (any size)** 5
Total

All age groups
N1aN1b
numbernumber
6
1
2
51
24
1
1
42
6

2
1
17
2
13
1
128
18

Continuation of Table 4.6

Total pT
number %
24
3.3
48
6.6
2
0.3
9
1.2
249
34.0
2
0.3
112
15.3
8
1.0
21
2.9
2
0.3
226
30.9
29
3.9

416 (56.8%) 134 (18.3%) 182 (24.9%) 732

100

M0
number
24
48
2
9
247
1
110
8
21
2
196
23

M1
number691 (94.4%)

41 (5.6)

M0
number
83
206
13
38
310
43
189
25
55
11
176
43

M1
number

2
1
2

30
6

4th period: surgery in 2005-2010
N0
pT/tumor size
numberpT1a (up to 5 mm) 79
pT1a (6-10 mm)
173
pT1am (1-5 mm)
11
pT1am (6-10 mm) 30
pT1b (11-20 mm) 228
pT1bm (11-20 mm) 32
pT2 (21-40 mm)
150
pT2m (21-40 mm) 16
pT3 (>40 mm)*44
pT3m (>40 mm)* 9
pT3 (any size)**70
pT3m (any size)** 13

All age groups
N1aN1b
numbernumber
1
3
24
9
1
1
6
2
62
20
8
3
25
16
3
6
11
2
34
88
8
26

Total

185 (15.3%) 174 (14.3%) 1214

855 (70.4%)

Total pT
number %
83
6.8
206
17.0
13
1.1
38
3.1
310
25.5
43
3.6
191
15.7
25
2.1
55
4.5
11
0.9
192
19.8
47
3.9
100

2

16
4

1192 (98.2%) 22 (1.8%)*- no extrathyroidal extension; ** - extrathyroidal extension

While during the first period of observation (1990-1994), the signs of extrathyroidal
extension were identified in 59.3% cases, their frequency gradually decreased
with increasing latency to 23.7% in 2005-2010. Such a tendency was also noted in
the analysis of the frequency of regional and distant metastases. The percentage
of cases with metastases to lymph nodes decreased from 62.3 to 29.6%, and that of
distant metastases to the lung (detected during postoperative treatment of patients withradioiodine), decreased from 26.9 to 1.8%. All the above changes were characterized bysignificantly descending linear trends (р=0.0001).
81

Chapter 4
The frequency of tumor foci detected in the form of separate lesions in contralaterallobe or sometimes in the affected lobe as well (Tm) in the first three time periods, i.e. during
1990-2004, practically did not differ (Table 4.7): 8.4% (14/167), 7.9% (29/365), and 7.1%
(52 cases out of 732). Only in 2005-2010, the frequency of multifocal tumors significantly
increased as compared with the first period of time (р=0.0309).
Also, it should be noted that before 2000, the “additional” tumoral foci which did not
differ structurally from the main tumor were mostly seen among cases of “aggressive”
PTCs sized more than 10 mm with signs of extrathyroidal extension and regional as well as
distant metastases (Table 4.6, 4.7 and Fig. 4.9).

Figure 4.9. Multifocal papillary thyroid carcinoma. (A) Nonencapsulated main tumor sized
15 mm in the left lobe, follicular variant with the solid growth pattern. Haematoxylin and eosin,
original magnification x10. (B) Multifocal lesion in the right lobe sized 5 mm with the solid-follicular
structure. Haematoxylin and eosin, original magnification x20.

In 2000-2004, and especially in 2005-2010, different foci of multifocal tumors werecharacterized by variations in size, including microtumors (Table 4.7), by the degree of
encapsulation, and by structural and invasive features. For an instance, in the same patient,
there might be an encapsulated tumor of mixed structure sized more than 10 mm, and aseparate nonencapsulated microtumor of mixed structure in one lobe (Fig. 4.10 A-E). In thecontralateral lobe there might be, again, an encapsulated tumor of mixed structure sized
more than 10 mm, and a nonencapsulated oxyphilic-cell tumor of the solid structure withsigns of marked intratumoral and peritumoral thyroiditis (Fig. 4.10 F-H). In this example
tumors are likely to be multiple PTCs developing independently.
Invasive features of PTCs also depended on patients’ age. The highest frequency oftumors displaying intrathyroidal and extrathyroidal extension, vascular invasion, regional
metastases to cervical lymph nodes and distant metastases to the lung was found inchildren (Table 4.8). For all these features, significantly descending linear age trends were
found (р=0.0001).
Morphological signs of aggressiveness (extrathyroidal extension, vascular invasion,
regional metastases) were revealed in all histological subtypes, mostly in nonencapsulated
tumors (Table 4.9). In encapsulated PTCs (Fig. 4.11), tumor capsule invasion was observedin most cases, intrathyroidal extension in not more than 40.0%, and was limited only toisolated tumoral foci outside the tumor in adjacent thyroid tissue (Fig. 4.11 D).
82

Thyroid cancer pathology in Ukraine after Chernobyl

Figure 4.10. Multiple papillary thyroid carcinomas revealed in the same patient. (A) Encapsulated
tumor in the right lobe sized 22 mm with the mixed growth pattern. Haematoxylin and eosin, original
magnification x10-panoramic. (B) High-power image of the same tumor. Macrofollicular growth
pattern. Haematoxylin and eosin, original magnification x100. (C) High-power image of the same
tumor. Microfollicular growth pattern. Haematoxylin and eosin, original magnification x100. (D)High-power image of the same tumor, different area. Solid-follicular component between fibrotic
stroma. Haematoxylin and eosin, original magnification x200. (E) Nonencapsulated tumor in the rightlobe sized 6 mm with the solid-follicular growth pattern and small papillary loci. Marked stromal fibrosis.
Haematoxylin and eosin, original magnification x20-panoramic. (F) Encapsulated tumor in the left lobe
sized 11 mm with the papillary-solid growth pattern. Evident tumor capsule invasion. Haematoxylin
and eosin, original magnification x20. (G) Nonencapsulated oxyphilic-cells tumor in the left lobe sized
9 mm with the solid and trabecular growth pattern. Evident intratumoral and peritumoral thyroiditis.
Haematoxylin and eosin, original magnification x20. (H) High-power of the same tumor. Intranuclear
pseudoinclusions in oxyphilic tumor cells. Haematoxylin and eosin, original magnification x200.

83

Chapter 4
Extrathyroidal extension was registered only in 1.2% cases in adults among fully
encapsulated tumors with subcapsular localization; regional metastases were found inisolated cases in each age group. Regional lymph node metastases in adults were more
frequently seen in the classic papillary variant than in follicular or solid variants (Table
4.10). A higher rate of lymph node metastases in encapsulated classical papillary thyroid
carcinomas was also reported in an independent study [51]. No distant metastases to thelung in patients with encapsulated РТС were found during the whole period of observation(Table 4.10). This is in excellent agreement with the opinion of J. Rosai: “Papillary thyroid
carcinoma totally surrounded by a capsule may still be associated with nodal metastases,
but the incidence of distant metastases or tumor death is nearly zero” [4].
Table 4.7
Size of multifocal papillary thyroid carcinomas in patients born before Chernobyl
Children aged up to 14 years at surgery

Biggestlesion,mm

1990-1994

1995-1999

2000-2004

2005-2010

number %number %number %number %number%up to 5

-

-

-

-

-

-

-

-

-

-

6-10

-

-

-

-

-

-

-

-

-

-

11-20

3

23.1

1

11.1

-

-

-

-

4

18.2

21-30

4

30.7

-

-

-

-

-

-

4

18.2

31-40

1

7.7

-

-

-

-

-

-

1

4.5

41-50

3

23.1

1

11.1

-

-

-

-

4

18.2

51-60

1

7.7

4

44.5

-

-

-

-

5

22.7

>60

1

7.7

3

33.3

-

-

-

-

4

18.2

Total

13

100

9

100

0

-

-

22

100

1990-2010

Adolescents aged from 15 to 18 years at surgery
1990-1994

1995-1999

2000-2004

2005-2010

number %number %number %number %number%up to 5

-

-

-

-

-

-

-

-

-

-

6-10

-

-

-

-

1

10.0

-

-

1

5.2

11-20

-

-

4

50.0

4

40.0

-

-

8

42.1

21-30

-

-

1

12.5

3

30.0

-

-

4

21.1

31-40

1

100

2

25.0

1

10.0

-

-

4

21.1

41-50

-

-

1

12.5

1

10.0

-

-

2

10.5

51-60

-

-

-

-

-

-

-

-

-

-

>60

-

-

-

-

-

-

-

-

-

-

Total

1

100

8

100

10

100

-

-

19

100

84

1990-2010

Thyroid cancer pathology in Ukraine after Chernobyl
Continuation of Table 4.7

up to 5
6-10
11-20
21-30
31-40
41-50
51-60
>60
Total

1990-1994
number %0-

up to 5
6-10
11-20
21-30
31-40
41-50
51-60
>60
Total

1990-1994
number %
3
21.4
4
28.7
2
14.3
3
21.4
1
7.1
1
7.1
14
100

Adults aged from 19 to 42 years at surgery
1995-1999
2000-2004
2005-2010
number %number %number %
2
4.8
15
8.5
11
26.2 4424.8
5
41.7 1023.8 6235.0
216.7 819.0 21
11.9
2
4.8
17
9.6
5
11.9 10
5.6
1
8.3
4
9.5
4
2.3
4
33.3 42.3
12100 42100 177100
All age groups
1995-1999
2000-2004
2005-2010
number %number %number %
2
3.8
15
8.5
12
23.1 4424.8
1034.5 1426.9 6235.0
3
10.3 1121.2 21
11.9
2
6.9
3
5.8
17
9.6
2
6.9
6
11.5 105.6
517.3 47.7
4
2.3
7
24.1 4
2.3
29
100 52100 177
100

1990-2010
number %
17
7.4
55
23.8
77
33.3
31
13.4
19
8.2
15
6.5
9
3.9
8
3.5
231
100
1990-2010
number %
17
6.3
56
20.6
89
32.7
39
14.3
24
8.8
21
7.7
14
5.1
12
4.5
272
100

In nonencapsulated PTCs, the most pronounced intrathyroidal extension was notedin the diffuse-sclerosing variant (Fig. 4.5A) apparently stemming from its definition. For
patients of all ages with diffuse sclerosing variant of PTC, a high frequency of extrathyroidal
extension and metastases to lymph nodes was registered as well (Table 4.9). Metastases
most commonly had papillary-solid structure with marked signs of oxyphilic-cell andsquamous-cell metaplasia (Fig. 4.12). In children and adolescents with diffuse sclerosing
variant of PTC, distant metastases to the lung were also found in 23.5 and 25.0% cases,
respectively. These data additionally attest to the aggressive behaviour of this variant of
PTC [1,3,4,29], but, as already mentioned above, the small number of cases does not allow
establishing a link between such a tumor structure and exposure to Chernobyl fallout.
Our review of the three main subtypes of PTC (classic papillary, follicular and solid)
and of the mixed-type PTC shows that the identification of the (formerly) “childhood
variant” [17,38] which combines - as already pointed out - tumors with solid, follicular,
and solid-follicular structures, was pathologically justified. All signs of aggressiveness:
vascular invasion, multifocality, extrathyroidal extension, regional lymph node and distantmetastases were most pronounced namely in children who had nonencapsulated tumors
with such structure (Table 4.9).
85

Chapter 4

Figure 4.11. Fully encapsulated papillary thyroid carcinomas. (A) Tumor with the follicular
growth pattern. Evident tumor capsule invasion and central fibrosis. Haematoxylin and eosin, original
magnification x20-panoramic. (B) Tumor with the solid-follicular growth pattern. Haematoxylin andeosin, original magnification x20-panoramic. (C) Tumor with the papillary growth pattern. Tumor capsuleinvasion. Haematoxylin and eosin, original magnification x50. (D) Tumor with solid-follicular growth
pattern. Intrathyroidal extension of the tumor. Haematoxylin and eosin, original magnification x50.

Figure 4.12. Lymph node metastases of the diffuse-sclerosing variant of papillary thyroid
carcinomas. (A) Papillary-solid growth pattern. Haematoxylin and eosin, original magnification x10panoramic. (B) Papillary growth pattern. Cystic changes, numerous psammoma bodies, extra-lymph
node extension. Haematoxylin and eosin, original magnification x20. (C) Papillary-solid growth
pattern. Evident oxyphilic-cell metaplasia. Haematoxylin and eosin, original magnification x20.

86

Intrathyroidal
extension
number %
21
70.0
32
49.2
33
57.9
8
56.0
5
45.5
2
66.7
50
68.5
17
100
168
61.8

Intrathyroidal
extension
number %
26
54.2
24
51.1
17
70.8
17
44.7
12
66.7
3
60.0
26
65.0
4
100
129
57.3

Subtype(number)PV (30)FV (65)
SV (57)PFV (16)
PSV (11)
PSFV (3)
SFV (73)
DSV (17)Warthin (0)Cribriform (0)Total (272)PV (48)FV (47)
SV (24)PFV (38)
PSV (18)
PSFV (5)
SFV (40)
DSV (4)Warthin (1)Cribriform (0)Total (225)

Lymphatic
invasion
number %
20
66.7
40
61.5
43
75.4
9
56.3
5
45.5
1
33.3
54
74.0
17
100
189
69.5

Children aged up to 14 years at surgery
Vascular
Extrathyroidal
invasion
Multifocality
extension
number %number %number%1
3.3 1446.7
25
38.5 4
6.2
43
66.2
23
40.4 812.3 50
87.7
1
6.3 1
6.3
8
50.0
2
18.2 1
9.1
4
36.4
2
66.7
31
42.5 811.0 58
79.5
7
41.2
83
30.5 22
8.1
186
68.4
Adolescents aged from 15 to 18 years at surgery
Lymphatic
Vascular
Extrathyroidal
invasioninvasion
Multifocality
extension
number %number %number %number%2245.8 3
6.3 3
6.3
18
37.5
21
44.7 1123.4 1
2.1
19
40.4
11
45.8 1145.8 312.5 1562.5
1334.2 513.2 410.5 1642.1
633.3 2
11.1 316.7 950.0
360.0 120.0 360.0
2076.9 922.5 5
12.5 21
52.5
4
100
4
100
100
44.4 4218.7 19
8.4
105
46.7

Table 4.8
Invasive properties of papillary thyroid carcinoma in patients born before Chernobyl

Regional mts
number %
22
45.8
22
46.8
10
41.7
20
52.6
13
72.2
5
100
22
55.0
4
100
118
52.4

Regional mts
number %
16
53.3
38
58.5
45
78.9
11
68.8
9
81.8
3
100
53
72.6
9
52.9
184
67.6

Distant mts
number %
5
10.4
6
12.8
4
16.7
5
13.2
4
22.2
2
40.0
12
30.0
1
25.0
39
17.3

Distant mts
number %
4
13.3
21
32.3
19
33.3
4
25.0
1
9.1
23
31.5
4
23.5
76
27.9

Thyroid cancer pathology in Ukraine after Chernobyl

87

88

Lymphatic
invasion
number %
203
30.4
58
17.5
39
33.1
129
30.6
65
45.5
20
41.7
50
22.4
6
100
6
31.6
1
50.0
577
29.1

Adults aged from 19 to 42 years at surgery
Vascular
Extrathyroidal
invasion
Multifocality
extension
number %number %number %29
4.3
69
10.3 13319.9
4914.8 38
11.4 6319.0
37
31.4 17
14.4 4134.7
4711.1 45
10.7 13632.2
2114.7 20
14.0 4732.9
1632.7 714.3 1428.6
49
22.0 32
14.3 48
21.5
5
83.3
3
15.8 315.8 421.1
150.0 252
12.7 231
11.7 491
24.8
Regional mts
number %
225
33.7
79
23.6
35
29.7
192
45.5
59
41.3
17
34.7
63
23.8
6
100
7
36.8
1
50.0
674
34.0

Distant mts
number %
10
1.5
8
2.4
6
5.1
19
4.5
9
6.3
4
8.2
9
4.0
65
3.3

Subtype(number)PV (26)
FV (57)
SV (54)PFV (14)
PSV (11)
PSFV (3)
SFV (69)
DSV (17)Warthin (0)Cribriform (0)Total (251)Intrathyroidal
extension
number %
18
69.2
31
54.4
31
57.4
7
50.0
5
45.5
2
66.7
49
71.0
17
100
160
63.7

Lymphatic
invasion
number %
17
65.4
38
66.7
42
77.8
9
64.3
5
45.5
1
33.3
53
71.0
17
100
182
72.5

Children aged up to 14 years at surgery
Vascular
Extrathyroidal
invasion
Multifocality
extension
number %number %number %
1
3.8
14
53.8
21
36.8 4
7.0 4375.4
2240.7 814.8 50
92.6
1
7.1
1
7.1 8
57.1
2
18.2 1
9.1 4
36.4
2
66.7
30
43.5 8
11.6 58
84.1
7
41.2
77
30.7 22
8.8 186
74.1

Regional mts
number %
15
57.7
37
64.9
44
81.5
10
71.4
9
81.8
3
100
53
76.8
9
52.9
180
71.7

Distant mts
number %
4
15.4
21
36.8
19
35.2
4
28.6
1
9.1
23
33.3
4
23.5
76
30.3

Table 4.9
Invasive properties of nonencapsulated and partly encapsulated papillary thyroid carcinoma in patients born before Chernobyl

Subtype(number)PV (667)
FV (332)
SV (118)
PFV (422)
PSV (143)
PSFV (49)
SFV (223)
DSV (6)Warthin (19)
Cribriform (2)Total (1981)

Intrathyroidal
extension
number %
200
30.0
100
30.1
40
33.9
170
40.3
61
42.7
25
51.0
65
29.1
6
100
5
26.3
2
100
674
34.0

Continuation of Table 4.8

Chapter 4

Intrathyroidal
extension
number %
22
55.0
21
52.5
16
69.5
15
48.4
11
73.3
3
60.0
23
74.2
4
100
115
60.5

Intrathyroidal
extension
number %
145
29.1
73
41.0
33
44.6
39.9
134
53
41.4
18
54.5
45
36.3
6
100
5
26.3
2
100
514
36.7

Subtype(num)
PV (40)FV (40)SV (23)
PFV (31)
PSV (15)
PSFV (5)
SFV (31)
DSV (4)Warthin (1)Cribriform (0)Total (190)PV (499)
FV (178)
SV (74)PFV (336)
PSV (128)
PSFV (33)
SFV (124)
DSV (6)Warthin (19)
Cribriform (2)Total (1399)

Adolescents aged from 15 to 18 years at surgery
Vascular
Extrathyroidal
invasion
Multifocality
extension
number %number %number %
3
7.5
3
7.5
18
45.0
11
27.5
1
2.5
19
47.5
11
47.8
3
13.0
15
65.2
5
16.1
3
9.7
16
51.6
2
13.3
3
20.0
9
60.0
1
20.0
3
60.0
7
22.6
5
16.1
21
67.7
4
100
40
21.1
18
9.5
105
55.3
Adults aged from 19 to 42 years at surgery
Lymphatic
Vascular
Extrathyroidal
invasioninvasion
Multifocality
extension
number %number %number %number %170
34.1 214.2
57
11.4 12925.9
4827.0 24
13.4
16
9.0
63
35.4
36
48.6 2432.4
1332.4 4054.1
113
33.6 3711.0
3610.7 13640.5
6147.7 1612.5
20
15.6 4535.2
1751.5 1339.4
4
12.1 1442.4
4637.1 2419.4
2419.4 48
38.7
6
100 5
83.3
6
31.6 315.8
315.8 421.1
150.0 150.0
504
36.0 163
11.7 173
12.4 484
34.6

Lymphatic
invasion
number %
21
52.5
19
47.5
10
43.5
12
38.7
6
40.0
3
60.0
18
58.1
4
100
93
48.9

Regional mts
number %
210
42.1
72
40.4
33
44.6
185
55.0
58
45.3
17
51.5
52
41.9
6
100
7
36.8
1
50.0
641
45.8

Regional mts
number %
20
50.0
21
52.5
10
43.5
20
64.5
13
86.7
5
100
22
71.0
4
100
115
60.5

Distant mts
number %
10
2.0
8
4.5
6
8.1
19
5.7
9
7.0
4
12.1
9
7.3
65
4.6

Distant mts
number %
5
12.5
6
15.0
4
17.4
5
16.1
4
26.7
2
40.0
12
38.7
1
25.0
39
20.5

Continuation of Table 4.9

Thyroid cancer pathology in Ukraine after Chernobyl

89

90

Tum capsule
Subtypeinvasion(number) number %PV (4)
4100
FV (8)7
87.5
SV (3)
3100
PFV (2)2100
PSV (0)
PSFV (0) SFV (4)1
25.0
Total (21) 17
81.0

Intrathyroid
extension
number %
3
75.0
1
12.5
2
66.7
1
50.0
1
25.0
8
38.1

Children aged up to 14 years at surgery
Lymphatic
Vascular
Extrathyroid
invasioninvasion
Multifocality
extension
Regional mts Distant mts
number %number %number %number %number %number %3
75.0 125.0 225.0 450.0 1
12.5 133.8 133.3 133.3 150.0 125.0 125.0 733.3 6
28.6 00
4
19.0 0Adolescents aged from 15 to 18 years at surgery
Tum capsule
Intrathyroid
Lymphatic
Vascular
Extrathyroid
Subtypeinvasion
extension
invasioninvasion
Multifocality
extension
Regional mts Distant mts(number) number %number%number %number %number %number % number %number %PV (8)
8100 450.0 1
12.5 225.0 FV (7)7100 3
42.9 228.6 114.8 SV (1)
1
100 1
100 1
100 PFV (7)7
100 2
28.6 1
14.3 1
14.3 PSV (3)3
100 1
33.3 PSFV (0)SFV (9)9100 3
33.3 222.2 222.2 Total (35) 35
100 1440.0 720.0 2
5.7 1
2.9
0
3
8.6 0
Adults aged from 19 to 42 years at surgery
Tum capsule
Intrathyroid
Lymphatic
Vascular
Extrathyroidal
Subtypeinvasion
extension
invasioninvasion
Multifocality
extension
Regional mts Distant mts(number) number %number %number %number %number %number %number %number %PV (168)167
99.4 55
32.7 33
19.6 84.8
12
7.1
4
2.4 15
8.9
FV (154)129
83.8 2717.5 10
6.5 2516.2 2214.3 7
4.5
SV (44)39
88.6 715.9 3
6.8 1329.5 4
9.1
1
2.3 2
4.5
PFV (86)82
95.3 3641.9 16
18.6 10
11.6 910.5 7
8.1
PSV (15)
13
86.7 853.3 426.7 533.3 2
13.3 1
6.7
PSFV (16) 14
87.5 743.8 318.8 318.8 318.8 SFV (99)82
82.8 20
20.2 4
4.0 2525.3 88.1
1
1.0
Total (582) 531
91.2 160
27.5 73
12.5 89
15.3 58
10.0 7
1.2 33
5.7
0-Table 4.10
Invasive properties of fully encapsulated papillary thyroid carcinoma in patients born before Chernobyl

Chapter 4

Thyroid cancer pathology in Ukraine after Chernobyl
By contrast, in adolescents and adults with tumors of such structural “combination”, nosigns of the higher aggressiveness were found. This may probably be due to the fact that thearchitecture of the follicular variant in adolescents and adults differs from that in children.
In older patients, the solid component is absent or confined to very small foci in the areasof invasive growth. On the other hand, when combining tumors with the solid and solidfollicular structure in adolescents and adults, the frequency of extrathyroidal extension was
significantly higher (р<0.05) as compared to other subtypes: in adolescents 66.7% (36/54
cases of the solid and solid-follicular subtypes) vs 50.7% (69/136 cases of other subtypes),and 44.4% (88/198 cases of the solid and solid-follicular subtypes) vs 33.0% (396/1201
cases of other subtypes) in adults. In addition, in the adult group, such a pooling showeda significantly higher frequency, as compared to other subtypes, of vascular invasion(р<0.001), multifocality (р<0.01) and distant metastases (Table 4.9). Thus, despite the findingthat the prevalence of РТСs with the solid and solid-follicular structure was significantly
declining with increasing patients’ age and latency, morphological signs of aggressivenessin such tumors were still preserved.
According to the WHO classification [5], papillary microcarcinoma represented by thetumors sized up to 10 mm is considered to be an independent subtype. We already notedthat the prevalence of microcarcinomas in the groups under study was significantly risingwith increasing age of patients and latency (Table 4.3), i.e. time elapsed after Chernobyl.
The presence of the “full” capsule (Fig. 4.13 A) was found in 20.8% tumors sized up to 5
mm (26/125) and in 22.4% (83/170) sized from 6 to 10 mm, i.e. most “small” tumors were
nonencapsulated (Fig. 4.13 B-C).

Figure 4.13. Papillary microcarcinomas. (A) Fully encapsulated tumor sized 7 mm with thepapillary growth pattern. Haematoxylin and eosin, original magnification x20-panoramic. (B)Nonencapsulated tumor sized 7 mm with the solid growth pattern. Tumoral extension to the thyroid
capsule and adjacent thyroid tissue. Haematoxylin and eosin, original magnification x20. (C) Tumor
sized 5 mm with the papillary-solid growth pattern. Extrathyroidal extension, marked intratumoral
fibrosis. Haematoxylin and eosin, original magnification x10.

91

Chapter 4
Microcarcinomas, similarly to large size РТСs, may have different structure: classic
papillary (Fig. 4.13 A), follicular, solid (Fig. 4.13 B) or mixed (Fig. 4.13 C). No statisticallysignificant predominance of any histological variant – among both encapsulated andnonencapsulated tumors – was found in microcarcinomas (Table 4.11, 4.12).
The invasive features of microcarcinoma depended on tumor size and encapsulation.
Encapsulated tumors sized up to 5 mm, regardless of architecture, were minimally invasivein all 26 cases. Although tumor cells might display signs of invasion into the tumor capsule,
not a single case showed spread outside its limits; there were no signs of vascular invasion
or metastases to lymph nodes. In three cases (11.5%) diagnosed during the last period of
observation microtumors were multiple, as was mentioned above.
Table 4.11
Subtypes of fully encapsulated micro-PTC in patients born before Chernobyl

Subtype
PV
FV
SV
PFV
PSV
PSFV
SFV
Warthin
Cribriform
Total

PV
FV
SV
PFV
PSV
PSFV
SFV
Warthin
Cribriform
Total

1990-1994
number %-sized from 1 to 5 mm
All age groups
1995-1999
2000-2004
number %number %
2
40.0
1
20.0
1
20.0
1
20.0
5
100

2005-2010
number %
7
33.3
7
33.3
1
4.8
2
9.5
1
4.8
1
4.8
2
9.5
21
100

1990-2010
number %
9
34.7
8
30.8
1
3.8
2
7.7
2
7.7
1
3.8
3
11.5
26
100

1990-1994
number%-sized from 6 to 10 mm
All age groups
1995-1999
2000-2004
2005-2010
number %number %number %3
30.0 535.7 1525.0
220.0 428.6 1220.0
1
10.0 915.0
220.0 321.5 1016.7
220.0 1
7.1 2
3.3
5
8.3
1
7.1 7
11.7
10
100 14100 60100

1990-2010
number %
23
27.4
18
21.4
10
11.9
15
17.8
5
6.0
5
6.0
8
9.5
84
100

Encapsulated microcarcinomas sized from 6 to 10 mm were also minimally invasive in
general. However, in two cases out of 84 (2.4%), in the presence of follicular or papillaryfollicular structures, there were metastases to lymph nodes (N1a); in 7 cases (8.3%) signs oflymphatic invasion, and in 7 cases (8.3%) multiple microtumors were seen.
92

Thyroid cancer pathology in Ukraine after Chernobyl
Nonencapsulated microcarcinomas, similarly to the tumors of larger size, werecharacterized by the more pronounced invasive features as compared to encapsulated ones.
Even very small tumors (up to 5 mm) of the follicular, solid, and mixed structure displayedsigns of moderate intrathyroidal spread in 11.1% cases (11/99), lymphatic invasion in 8.1%
(8/99), vascular invasion in 1.0% (1/99), extrathyroidal extension in 2.0% (2/99, Fig. 4.13C),
and metastases to lymph nodes (N1a) in 6.1% of cases (6/99).
Table 4.12
Subtypes of nonencapsulated and partly encapsulated micro-PTC
in patients born before Chernobyl
sized from 1 to 5 mm
Subtype

PV
FV
SV
PFV
PSV
PSFV
SFV
Warthin
Cribriform
Total

PV
FV
SV
PFV
PSV
PSFV
SFV
Warthin
Cribriform
Total

All age groups
2000-2004
number %
7
33.3
6
28.5
1
4.8
3
14.3
1
4.8
1
4.8
2
9.5
21
100

1990-1994
number %
1
100
1
100

1995-1999
number %-2005-2010
number %
10
13.0
17
22.1
9
11.7
13
16.9
9
11.7
18
23.3
1
1.3
77
100

1990-2010
number %
18
18.2
23
23.2
10
10.1
16
16.2
10
10.1
1
1.0
20
20.2
1
1.0
99
100

1990-1994
number
%
1
25.0
2
50.0
1
25.0
4
100

sized from 6 to 10 mm
All age groups
1995-1999
2000-2004
2005-2010
number %number %number %2
18.2 2138.2 75
34.7
1
9.1
8
14.5 28
13.0
1
9.1
1
1.8
10
4.6
2
18.2 15
27.3 47
21.8
2
18.2 5
9.1
26
12.0
9
4.2
3
27.2 5
9.1
20
9.2
1
0.5
11
100 55100
216
100

1990-2010
number %
98
34.3
38
13.3
14
4.9
64
22.4
33
11.5
9
3.1
29
10.1
1
0.4
286
100

Invasiveness of the tumors sized from 6 to 10 mm was significantly higher comparedto that of microcarcinomas sized up to 5 mm: intrathyroidal extension was observed in
22.0% (63 out of 286 cases, р=0.0178); lymphatic invasion in 24.8% (71/286, р=0.0003);
extrathyroidal extension in 16.1% (46/286, р=0.0001); lymph node metastases in 23.3%(67/286, р=0.0001). However, all these were significantly lower than in nonencapsulated
93

Chapter 4
carcinomas sized more than 10 mm for all age groups (Table 4.9). It should be emphasizedthat not in a single case of PTC sized up to 10 mm distant metastases to the lung weredetected in the course of postoperative follow-up of patients.
In Belarus, by contrast with Ukraine, the prevalence of post-Chernobyl microcarcinomas
was much higher: 39.2% just in children operated on at the age under 15 years [52,53];
in some cases distant metastases to the lung were identified [54]. Thus, tumor size alone
cannot be a determinant of the choice of treatment tactics.
Table 4.13
Concomitant thyroid diseases in patients with micro-PTC born before Chernobyl
sized from 1 to 5 mm
1990-1994
Pathology number %
FTC
MTC
FA
Nodule
MNG
1/1
Graves’Chronic
thyroiditis Total
1/1
-

FTC
MTC
FA
NoduleMNG
Graves’Chronic
thyroiditis
Total

1995-1999
number %-All age groups
2000-2004
2005-2010
number %number %5/26
19.2 19/98
19.4
6/26
23.1 15/98
15.4
4/26
15.4 18/98
18.4
4/26
15.4 22/98
22.4

0

4/26
23/26

-

15.4 6/98
88.5 80/98

sized from 6 to 10 mm

6.1 10/125 8.0
81.6 104/125 83.2

1990-1994
number %-All age groups
1995-1999
2000-2004
2005-2010
number %number %number %8/69
11.6 16/276 5.8
3/21
14.3 7/69
10.1 29/276 10.5
2/21
9.5 3/69
4.3 20/276 7.2
2/276
0.7

0/4

3/21
8/21

-

14.3 3/69
38.1 21/69

1990-2010
number %24/125 19.2
21/125 16.8
23/125 18.4
26/125 20.8

1990-2010
number %24/370
6.5
39/37010.5
25/370
6.8
2/370
0.5

4.3 62/276 22.4 68/370
30.4 129/276 46.6 158/370

18.4
42.7

Modern diagnostic methods allow detection of tumors even of minimal size. Our analysisof the presented material shows that thyroid nodule, multiple nodules, and Graves’ disease
were the reason for surgical intervention in 75.2% of cases of microcarcinoma sized up to
5 mm, and only in 24.3% cases sized from 6 to 10 mm. In the rest of cases, the papillary
microcarcinoma was the main thyroid disease, and the main reason for surgery (Table 4.13).
Concomitant chronic thyroiditis (presented in Table 4.13) was not the reason for surgery.
Undoubtedly, tumors sized up to 1-2 mm could be detected incidentally only on microscopic
examination of histological specimens from operated patients. If surgery was performed94

Thyroid cancer pathology in Ukraine after Chernobyl
for benign thyroid disease, e.g. multinodular goiter or Graves’ disease (Fig. 4.14 A-B),
such microcarcinomas are considered to be “occult”. The presence of microcarcinomas
sized 2 mm and larger may be suspected at a thorough examination of surgical material
and during sample selection for subsequent microscopic analysis as demonstrated in thecase of follicular adenoma (Fig. 4.14 C).

Figure 4.14. Occult papillary microcarcinomas. (A, B) Nonencapsulated micro-PTCs sized 2 mm
and 0.3 mm with the follicular growth pattern revealed in patients with Graves’ disease. Haematoxylin
and eosin, original magnification x20, x100. (C) Nonencapsulated micro-PTCs sized 3 mm with thepapillary-follicular growth pattern revealed in patients with follicular adenoma (FA). Haematoxylin
and eosin, original magnification x20.

As a whole, our analysis of 2,478 cases of PTC showed the presence of concomitant
thyroid disease in children in 11.0%, in adolescents in 16.9%, and in adults in 33.1% cases(Table 4.14). There was a significant ascending age-related linear trend (р=0.0001). The
frequency of concomitant thyroid disease was also increasing in time from the first (19901994) to the last (2005-2010) period of observation (р=0.0001 for trend).
Besides the concomitant benign thyroid disease, additional coexisting thyroid cancers
of smaller size than the PTC were noted in several cases; for this reason such tumors werereferred to as “concomitant”. In 2 cases these were FTCs and in 2 cases MTCs (Table 4.14). One
MTC in a boy who underwent hemithyroidectomy at the age of 7 years for a PTC with the solid
structure, was diagnosed at repeated surgery (completion thyroidectomy, neck dissection atlevel VI) two years later [11,42]. The second MTC, sized 7 mm, was identified in the left lobe ofa female patient aged 25 years with a PTC sized 11 mm in the right lobe (Fig. 15 A-C).
Follicular adenomas were concomitant to PTC only in adults, beginning from the period
2000-2004 (2.8%), and their frequency somewhat increased, though insignificantly, in thelast period of observation (4.4%).
Solitary and multiple (MNG) hyperplastic nodules were identified in all groups; theirfrequency significantly increased in a pairwise comparison: from 1.2% in children to 10.2%
in adults (р=0.0001), and from 0.6% in 1990-1994 to 12.7% in 2005-2010 (р=0.0001); theascending linear age and time trends were also significant (р=0.0001).
95

Chapter 4

Figure 4.15. Two types of thyroid cancer coexisting in the same patient. (A) Nonencapsulated
PTC with the papillary-solid growth pattern. Pronounced oxyphilic-cell metaplasia, Warthin-like loci.
Haematoxylin and eosin, original magnification x20. (B) Nonencapsulated micro-medullary thyroid
carcinoma with the solid growth pattern. Haematoxylin and eosin, original magnification x20. (C)Immunostaining of same area for calcitonin, original magnification x20.

PTCs in patients with Graves’ disease were detected in a small number of cases (1.6%),
only in adults and only beginning from 2000, i.e. from the age of 32 years old. These weremainly “occult” cancers or those detected at visual examination of surgical material. PTCs
sized more than 10 mm in patients with Graves’ disease were identified only in two cases.
The frequency of concomitant marked chronic thyroiditis of grade 3+/4+ (focal
thyroiditis of grade 1+/2+ was not taken into account) practically did not differ between
children and adolescents (9.6% and 10.7%, respectively) but was significantly increased in
adults in a pairwise comparison with both children (р=0.0011) and adolescents (р=0.0105).
A significant increasе over time was observed between the first and last periods ofobservation (р=0.0007); the corresponding linear trend was also significant (р=0.0001).
Thus, most morphological characteristics of PTC in children, adolescents and adults who
were aged up to 18 years during Chernobyl accident, have two main patterns: age-related
and time-related, which displayed significantly descending or ascending linear trends.
Considering other types of thyroid cancer, it should be noted that follicular thyroid
carcinoma (FTC) was detected in Ukraine in a small percentage of cases: 2.8% in children,
7.3% in adolescents, and 5.2% in adults (Table 4.2), similarly to other countries affected by
the Chernobyl catastrophe [7,10,14].
The tumors under study represented encapsulated solitary nodules exceeding 2 cm inmore than 70% of cases (in all age groups). Tumors sized less than 1 cm were detected
in 1 out of 18 cases in adolescents (5.6%) and in 7 out of 111 cases in adults (6.3%). Most
FTCs had microfollicular-solid structure. The oxyphilic-cell variant of FTC was not foundin children, but was identified in 2 cases in adolescents (11.1%) and in 11 cases (9.9%) in
adults. The diagnosis of “follicular thyroid carcinoma” was based on generally accepted
criteria: marked ”hook-like” or “mushroom-like” expansion through the tumor capsule and/or in blood vessels of the tumor capsule (Fig. 4.16).
96

Thyroid cancer pathology in Ukraine after Chernobyl
Table 4.14
Сoncomitant thyroid diseases in patients with PTC born before Chernobyl
Children aged up to 14 years at surgery
1990-1994
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number%number %Pathology number %FTC
MTC
1/127* 0.8 1/272
0.4
FA
Nodule
1/135
7.4
1/272
0.4
MNG
1/127
0.8 1/135
7.4
2/272
0.8
Graves’Chronic
thyroiditis 8/127
6.3 16/135 11.9 2/10
20.0 26/272
9.6
Total
10/127 7.9 18/135 13.3 2/10
20.0 30/272
11.0* - MTC, 12 mm, n/encaps, sol,T3N0M0
Adolescents aged from 15 to 18 years at surgery
1990-1994
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number%number %FTC
1/117* 0.9
1/225
0.4
MTC
FA
2/81
2.5
4/117
3.4
6/225
2.7
Nodule
2/81
2.5
3/117
2.6
5/225
2.2
MNG
1/81
1.8
1/117
0.9
2/225
0.9
Graves’Chronic
thyroiditis 1/27
3.7 9/81
11.1 14/117 12.0 24/225
10.7
Total
1/27
3.7 14/81
17.3 23/117 19.7 38/225
16.9* - FTC, 12 mm, microfol, T1bN0M0
Adults aged from 19 to 42 years at surgery
1990-1994
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number%number %FTC
1/1214*0.1 1/1981
0.05
MTC
1/1214** 0.1 1/1981
0.05
FA
17/605 2.8
53/1214 4.4 70/1981 3.5
Nodule3/149
2.0
30/605 5.0
89/1214 7.3 122/1981 6.2
MNG
2/149
1.3
12/605 2.0
66/1214 5.4 80/1981 4.0
Graves’
6/605
1.0
26/1214 2.1 32/1981 1.6
Chronic
thyroiditis 1/13
7.7 21/149 14.1 104/605 17.2 224/1214 18.5 350/1981 17.7
Total
1/13
7.7 26/149 17.4 169/605 27.9 460/1214 37.9 656/1981 33.1
* - FTC, 10 mm, T1aN0M0; ** - MTC, 7 mm, encaps, sol, T1aN0M097

Chapter 4
Continuation of Table 4.14

FTC
MTC
FA
NoduleMNG
Graves’Chronic
thyroiditis
Total

1990-1994
number %
1/167
0.6
1/167
0.6
-

1995-1999
number %
2/365
0.5
6/365
1.6
4/365
1.1
-

10/167
12/16746/36558/365

6.0
7.2

All age groups
2000-2004
2005-2010
number %number%
1/732
0.1
1/121401
1/12140.1
21/732 2.9
53/1214 4.4
33/732 4.5
89/1214 7.3
13/732 1.8
66/1214 5.4
6/732
0.8
26/1214 2.1

1990-2010
number %2/24780.1
2/24780.1
76/2478 3.0
128/2478 5.2
84/2478 3.4
32/2478 1.3

12.6 120/732 16.4 224/1214 18.5 400/2478 16.1
15.9 194/732 26.5 460/1214 37.9 724/2478 29.2

Invasion of two and more capsular vessels was found in 108 out of 137 cases (78.8%);
therefore, 21.2% of FTCs in children and adolescents born before Chernobyl were minimallyinvasive. An aggressive widely invasive FTC with extension to extrathyroidal connective
tissue and the trachea, with regional metastases to lymph nodes and distant metastases tothe lung (pT4aN1aM1) was observed only in one case in an adolescent female patient aged
15 years whom we described earlier [42].

Figure 4.16. Follicular thyroid carcinomas. (A) Mushroom-like expansion through the capsule.
Haematoxylin and eosin, original magnification x10. (B) Capsular invasion in a hook-like fashion.
Haematoxylin and eosin, original magnification x50. (C, D) Vascular invasion. Aggregates oftumor cells are seen within the vessel lumen attached to the wall and covered by endothelium.
Haematoxylin and eosin, original magnification x100, x50.

98

Thyroid cancer pathology in Ukraine after Chernobyl
Among thyroid diseases concomitant to FTC, PTC (represented mostly by
microcarcinomas sized up to 10 mm) was detected in 5 adults (Table 4.15). In 1 case, an
encapsulated PTC sized 21 mm was smaller than the coexisting FTC nodule (35 mm), andtherefore it was referred to the category of “concomitant disease”. Solitary and multiple
hyperplastic nodules were identified in 5.1%, chronic thyroiditis in the extratumoral tissue
in 10.2% of cases.
There are different opinions regarding the impact of radiation exposure on thedevelopment of FTC. Some authors suggest the existence of such [3,26,55] while other [56]have not revealed significant link between FTC and previous exposure.
Our analysis of the frequency of FTC in Ukraine after Chernobyl in the group at high risk forradiation-induced thyroid cancer showed no significant differences between different age
groups. However, a comparison of the frequency of FTC for different time periods after theaccident revealed a significantly increasing linear trend (р=0.0334). Undoubtedly, 137 FTCs
comprise too small number as compared to 2,478 PTCs, and further special investigations areneeded to draw valid conclusions regarding association with thyroid dose.
Medullary thyroid carcinoma (MTC) in the cohort under study was diagnosed even lessfrequently: 2.4% in children, 0.4% in adolescents, and 1.5% in adults (Table 4.2). Tumor size
varied from 4 to 75 mm; in 84.6% cases (33 out of 39) tumors were nonencapsulated, 87.2%
carcinomas (34 out of 39) had the solid structure (Fig. 4.17), and only 12.8% displayed“spindle cell-solid” growth pattern. In all cases there was a positive immunohistochemical
reaction with anti-calcitonin antibodies which confirmed the diagnosis of MTC. Sevenout of 8 MTCs in children and adolescents (87.5%) were characterized by extrathyroidal
extension, metastases to lymph nodes (T3N1bМ0); 2 of these patients had distantmetastases to the liver and brain (T3N1bM1). In adults, tumor aggressiveness was lesspronounced: extrathyroidal extension and regional metastases were found in 12 out of 31(38.7%) cases, distant metastases to the liver were detected in 1 female patient (3.2%). In
the latter patient with MEN 2A syndrome (she had been operated for pheochromocytoma
before), a papillary microcarcinoma sized 0.2 cm was identified (Fig. 4.18).
Here we do not analyze MTC in greater detail since many studies of post-Chernobyl
thyroid cancer have not revealed any effect of radiation on the risk for development oftumors of this type [7,10,11,14].
Poorly differentiated thyroid carcinoma (PDTC) was diagnosed in 4 cases, all in adultfemale patients, accounting for 0.2% of all cancers under study (Table 4.2). Two of themwere encapsulated, sized 26 and 35 mm, with trabecular-solid structure and invasion into
tumor capsule and capsular vessels (T2N0M0). Both carcinomas developed in the presenceof PTC as certain tumor areas displayed characteristic nuclear features. Two PDTCs were
nonencapsulated, sized 50 and 52 mm, were of the insular and solid structure (T3N1bM0). In
case of PDTC with the solid structure, the tumor was widely invasive (Fig. 4.19) with marked
intrathyroidal and extrathyroidal extension, and necrotic areas. Tumor cells had signs of
oxyphilic-cell metaplasia, were sometimes multinuclear, with marked nucleoli (Fig. 4.19
B). In some tumor areas, a focal positive reaction with anti-thyroglobulin antibodies was
revealed (Fig. 4.19 C); the reaction with anti-TTF-1 antibodies was diffuse and strong (Fig.
4.19 D). A high proliferative activity of the tumor was confirmed by the reaction with antiKi67 antibodies. In many areas there were more than 50.0% of positively stained nuclei (Fig.
4.19 E). In such areas up to 20.0% of nuclei were also positive for TP53 (Fig. 4.19 F).
99

Chapter 4

Figure 4.17. Medullary thyroid carcinoma. (A) Tumor with the solid growth pattern, marked
stromal fibrosis, extrathyroidal extension and central necrosis. Haematoxylin and eosin, original
magnification x10-panoramic. (B) Immunostaining for calcitonin of the same area, original
magnification x20. (C) Tumor with the solid growth pattern and vascular invasion. Haematoxylin
and eosin, original magnification x10. (D) Immunostaining for calcitonin of the same area. Marked
C-cell hyperplasia in peritumoral areas, original magnification x10.

Table 4.15
Concomitant thyroid diseases in patients with FTC born before Chernobyl
Children aged up to 14 years at surgery
1990-1994

1995-1999

2000-2004

2005-2010

1990-2010

Pathology number %number %number %number%number %

PTC

-

-

-

-

-

-

-

-

-

-

MTC

-

-

-

-

-

-

-

-

-

-

FA

-

-

-

-

-

-

-

-

-

-

Nodule

-

-

-

-

-

-

-

-

-

-

MNG

-

-

-

-

-

-

-

-

-

-

Graves’

-

-

-

-

-

-

-

-

-

-

Total

0/2

-

0/6

-

-

-

-

-

0/8

-

100

Thyroid cancer pathology in Ukraine after Chernobyl
Continuation of Table 4.15

PTC
MTC
FA
NoduleMNG
Graves’Chronic
thyroiditis
Total

1990-1994
number %-Adolescents aged from 15 to 18 years at surgery
1995-1999
2000-2004
2005-2010
1990-2010
number %number %number %number %2
20.0 211.1
1
10.0 15.6
114.3 1
5.6
-

1
1/1

1/7

-

1
14.3 4/10

10.0 40.0 -

-

2
6/18

11.1
33.3

1990-1994
number %-Adults aged from 19 to 40 years at surgery
1995-1999
2000-2004
2005-2010
number %number %number %
2*
4.4
3*
4.9
1
2.2
1
2.2
5
8.2
2
4.4
4
6.6
1
1.6

1990-2010
number %
5*
4.5
1
0.9
6
5.4
6
5.4
1
0.9

1990-1994
number %-All age groups
2000-2004
2005-2010
number %number %
2
3.6
3
4.9
3
5.5
5
8.2
2
3.6
2
3.6
4
6.6
1
1.6

1990-2010
number %
5
3.6
3
2.2
7
5.1
7
5.1
1
0.7

PTC
MTC
FA
NoduleMNG
Graves’Chronic
thyroiditis 48.9
813.1 12
10.8
Total
0/1
0/4
10/45
22.2 21/61
34.4 31/111 27.9
* - PTCs: 21 mm, encaps, FV, T2N0M0; 8 mm, partly encaps, FV, T1aN0M0; 7, 6, mm, n/encaps, FV,
T1aN0M0; 5 mm, n/encaps, PFV, T1aN0M0

PTC
MTC
FA
NoduleMNG
Graves’Chronic
thyroiditis
Total

1
1/4

1995-1999
number %-25.0 125.0 1/17

5.9
5.9

5
14/55

9.1
8
25.5 21/61

13.1 1434.4 37/137

10.2
27.0

101

Chapter 4

Figure 4.18. Coexistence of two different types of thyroid carcinomas in one patient. (A)Encapsulated papillary microcarcinoma sized 2 mm with the classic growth pattern and cystic
changes seen in vicinity to the nonencapsulated medullary thyroid carcinoma with the solid growth
pattern. Haematoxylin and eosin, original magnification x100. (B) Immunostaining for calcitonin of
the same area, original magnification x100. (C) Immunostaining for thyroglobulin of the same area,
original magnification x100.

In the most aggressive among all 4 PDTCs case, microfoci of PTC were also identified(Fig. 4.20). They were characterized by a strong reaction with antibodies to thyroglobulin(Fig. 4.20 D) and TTF-1 (Fig. 4.20 E), but unlike PDTC areas there were only isolated Ki67
positive nuclei (Fig. 4.20 F). TP53 expression was not detected in the PTC areas.
Tumor metastases completely replaced lymphatic nodes, and their structure andimmunohistochemical characteristics did not differ from those of the main tumor (Fig. 4.21).
The only difference was the lower frequency of nuclei positive for TP53: 5-10% (Fig. 4.21 F).
Modern handbooks of thyroid pathology do not consider the role of radiation in thedevelopment of PDTC [3,4]. However, at least some tumors may develop from preexistingwell-differentiated PTC or FTC. It could not be ruled out that radiation may promote
dedifferentiation of PTC cells. In our series, patients’ age was 21 and 24 (encapsulated
tumors) and 35 and 38 years old (nonencapsulated tumors), while typical mean age ofpatients with PDTC specified in handbooks is 55-60 years old. This issue, from our pointof view, deserves particular attention in future, because 3 out of 4 cases of PDTC weredetected in the last period of follow-up, namely, in 2008-2010.
Summarizing our data on pathology of thyroid cancer in Ukraine in the cohort aged
from 0 to 18 years at the time of the Chernobyl accident, it should be noted that for thewhole study period (1990-2010) the relative frequency of PTC exceeded 90.0% despite
patients’ age at surgery increased over this period from 4 (the youngest children operated
in 1990) to 42 years old (the oldest adults operated in 2010). Thus, PTC is undoubtedly thetype of radiogenic «Chernobyl» cancer; this may be considered a proven fact.
At the same time, a unique “structural portrait” of radiogenic Chernobyl PTC could
not been established either by our group in Ukraine, or other authors [14,23,53,57]. Most
likely, the development of PTC in patients of the group at risk (0 to 18 years at Chernobyl)
followed the common mechanisms of thyroid carcinogenesis (yet displaying a higher orlower frequency of certain genetic abnormalities which correlate with structural changes
in the tumor) that presumably underlie sporadic thyroid carcinogenesis.
102

Thyroid cancer pathology in Ukraine after Chernobyl

Figure 4.19. Poorly differentiated thyroid carcinoma. (A) Widely invasive nonencapsulated
tumor with the solid growth pattern. Marked fibrosis, necrotic foci, extrathyroidal extension.
Haematoxylin and eosin, original magnification x10-panoramic. (B) High-power image of the same
tumor. Numerous nuclei with prominent nucleoli. Haematoxylin and eosin, original magnification
x100. (C) Focal immunostaining for thyroglobulin, original magnification x100. (D) Diffuse strong
nuclear reactivity for TTF-1, original magnification x100. (E) Diffuse strong nuclear reactivity for Ki67.
Original magnification x100. (F) Moderate nuclear reactivity for TP53, original magnification x100.

Morphological characteristics of PTC are significantly changing with patients’ age
at surgery and over time after Chernobyl, i.e. with latency. Our analysis provides theevidence for two major patterns (age-related and time-related) seen for most pathologicalcharacteristics under study: “ascending” in some cases or “descending” in other linear trends.
Significantly descending age and time trends are found for the frequency of architecturally
less differentiated solid and solid-follicular subtypes of РТС, and invasive characteristics:
intrathyroidal and extrathyroidal extension, vascular invasion, regional metastases tolymph nodes and distant metastases to the lung, which are important and favorable forthe postoperative prognosis and patients’ quality of life.

103

Chapter 4

Figure 4.20. Microfoci of papillary thyroid carcinoma in poorly differentiated thyroid carcinoma.
(A) Fibrotic area with the papillary-follicular growth pattern. Haematoxylin and eosin, original
magnification x50-panoramic. (B) Microfoci with the follicular growth pattern. Haematoxylin andeosin, original magnification x100. (C) Microfoci with the follicular growth pattern and numerous
psammoma bodies in lymphatic vessel. Haematoxylin and eosin, original magnification x50. (D)Strong thyroglobulin immunostaining of PTC foci, original magnification x100. (E) Diffuse strong
nuclear reactivity for TTF-1 in both PTC and PDTC areas, original magnification x50. (F) Isolated Ki-67
positive nuclei in PTC foci. Original magnification x50.

Ascending linear trends are established for the frequency of structurally more differentiatedpapillary and papillary-follicular subtypes of РТС, for the prevalence of tumors sized up to 10
mm, and encapsulated tumors. These, again, may be considered as favorable, since “small” andencapsulated РТСs are characterized by significantly weaker invasive features compared withtumors of larger size and nonencapsulated ones. Thus, with increasing time after Chernobyl,
PTC, based on its morphological characteristics, clearly becomes less aggressive. It would be
difficult, however, to unambiguously determine if this is due only to the increasing patients’age or also to the increasing with age frequency of sporadic PTC.
104

Thyroid cancer pathology in Ukraine after Chernobyl

Figure 4.21. Lymph node metastasis of poorly differentiated thyroid carcinoma. (A) Metastasisof PDTC with the solid growth pattern completely replacing lymph node. Haematoxylin and eosin,
original magnification x10-panoramic. (B) High-power image of the same section. Numerous nuclei
with prominent nucleoli similar to those observed in the primary tumor. Haematoxylin and eosin,
original magnification x100. (C) Focal immunostaining for thyroglobulin, original magnification
x100. (D) Diffuse strong nuclear reactivity for TTF-1, original magnification x100. (E) Diffuse strong
nuclear reactivity for Ki67. Original magnification x100. (F) Focal nuclear reactivity for TP53 showing
labeling of 5% of the nuclei, original magnification x100.

As an attempt to at least partly answer this question, a comparative analysis ofmorphological characteristics of PTCs detected in age-matched groups of patients born
before Chernobyl (radiogenic РТСs) and after Chernobyl (sporadic, non-radiogenic РТСs)will be performed. The next chapter describes the results of such analysis.

105

Chapter 4
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108

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Chapter5

T Bogdanova, V Saenko, L Zurnadzhy,
I Likhtarov, L Kovgan, S Masiuk,
V Kashcheev, VA LiVolsi, ED Williams, M Ito,
M Mine, GA Thomas, M Tronko, S Yamashita

Comparative pathological analysis
of papillary thyroid carcinoma in age-matchedgroups of patients born before and after Chernobyl

The aim of this chapter is to comparе structural characteristics and invasive features ofpapillary thyroid carcinomas (PTCs) between the groups of patients who were children at
the time of the Chernobyl accident and thus were exposed to radioactive iodine in fallout(the radiogenic cancers) and those who were born since 1987 and were not irradiated (socalled sporadic cancers). We recognize that the radiogenic group will inevitably include
some cases of non-radiation aetiology, and attempted to minimize these through theprocess of selection described below.
In Chapter 3 and our previous papers [1-5] it has been shown that thyroid cancer
incidence was significantly higher in the six northern Ukraine regions with high levels ofcontamination by radioactive iodine. Among these, three areas are the most affected: Kiev,
Zhytomir, and Chernigov regions. A simple calculation of the number of cases per 1,000
residents in relevant populations for 25 years (from 1986 to 2010) demonstrates evident
difference: it is about 3 times higher in those exposed as children and 2 times higher inthose exposed as adolescents as compared with less contaminated regions (Table 5.1).
Table 5.1
Number of cases and prevalence per 1,000 of population of thyroid cancer cases in Ukraine
in subjects who were children and adolescents at the time of Chernobyl accidentChildren

Adolescents

5044/11100000=0.5/1000

1642/2200000=0.8/1000 6686/13300000=0.5/1000

21 less or notcontaminatedregions
2861/8900000=0.3/1000

1078/1760000=0.6/1000 3939/10660000=0.4/1000

3 out of 6 mostcontaminatedregions
1098/1025000=1.1/1000

254/195000=1.3/1000

Whole ofUkraineTotal

1352/1220000=1.1/1000

109

Chapter 5

Also, as was reported earlier [6-9], the highest dose-dependent additional incidence wasobserved in children whose age in 1986 did not exceed 4 years. It therefore is reasonable
to assume that the fraction of papillary carcinomas attributable to radiation would be thelargest among those whose age at exposure ranged from 0 to 4 years and who at the timeof accident were residents of the three most affected regions of Ukraine (Kiev, Chernigov,
and Zhytomir regions).
For this reason, for the present investigation we selected pathological data for theperiod from 1990 to 2010 (see Chapter 4), and included in the analysis only cases diagnosed
in residents of the three most contaminated regions who were aged up to 4 years at
Chernobyl. These are: 114 out of 272 PTCs in children aged up to 14 years at surgery, 66
out of 225 in adolescents aged from 15 to 18 years at surgery, and 59 out of 361 РТСs inadults aged 19-23 years. Age at surgery in adults was limited from 19 to 23 years sinceamong patients born after Chernobyl no one was older than 23 years in 2010. All 264 PTCs
detected in subjects born after the accident were included in the analysis regardless of
their place of residence because all these cases are sporadic. Characterstics of the agematched groups are specified in Table 5.2.
Table 5.2
Age-matched groups of radiogenic and sporadic PTC in the study
Number of cases
Radiogenic Sporadic
Children
114
111
Adolescents
66
97
Adults59
56

Mean ageRadiogenic
Sporadic
11.6
12.0
16.8
16.8
21.2
20.8

F:M
Radiogenic
68:46=1.5:1
44:22=2.0:1
44:15=2.9:1

Sporadic
83:28=3.0:1
72:25=2.9:1
46:10=4.6:1

In all groups, both in radiogenic and sporadic PTCs, female patients were prevailing,but in the group of children with radiogenic tumors the proportion of male patients was
greater as compared with the group of children with sporadic carcinomas (Table 5.2), witha substantial difference in F:M ratio (1.5:1 vs 3:1, respectively).
There were no significant differences in mean size of tumor when comparing either
different age groups or radiogenic and sporadic carcinomas in each age group. In children
with radiogenic РТС the frequency of microcarcinomas measuring up to 10 mm was
2.2 times lower as compared to children with sporadic РТС (Table 5.3) suggesting thatscreening had not shifted tumor size to the lower values in the exposed regions.
Table 5.3
Mean size of radiogenic and sporadic PTC in the study
ChildrenRadiogenic
Sporadic
Mean size(mm)≤10 mm:n (%)

110

AdolescentsRadiogenic
Sporadic

AdultsRadiogenic
Sporadic

23.6

24.0

19.1

23.3

20.6

21.3

7/114(6.1)

5/111(13.5)

14/66(21.2)

16/97(16.5)

13/59(22.0)

13/56(23.2)

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

It should be emphasized that “architecturally” all PTCs under study, regardless of patients’date of birth or age at diagnosis, were almost all represented by three common histologicalvariants: classical papillary, follicular, solid, and by the mixed-type tumors (herein reffered
to as “mixed variant”) which comprise combinations of the mentioned growth patterns.
The diffuse-sclerosing variant was identified in a small number of cases (mainly amongchildren), and there were isolated cases of Warthin-like and Cribriform-morular variants(Table 5.4). Among the mixed variants of PTC, the papillary-follicular and solid-follicular
combinations were most frequent (Table 5.5).
Comparison of radiogenic РТСs selected for the present analysis with all morphologicallystudied cases in patients born before the Chernobyl accident (described in the previous
chapter) shows that such a selection did not result in changes in the distribution of main
PTC subtypes, in the ratio of structural components of mixed variant, or frequency of the
combined (solid+solid-follicular and papillary+papillary-follicular) variants in all age groups(see Tables 4.4, 4.5 of Chapter 4 and Tables 5.4, 5.5, 5. 6 of this Chapter). Despite the maximum
age of adult patients has considerably decreased after selection (from 42 years in the totalgroup to 23 years in the selected group), all significant linear age trends (assessed by theChi-square test for trend) identified in the previous chapter, were preserved. In the selectedgroups of PTCs, linear decreasing trends of frequency of solid, solid-follicular and combined(solid+solid-follicular) variants (p<0.0115; p<0.0009; p<0.0001, respectively), and increasing
linear trends of frequency of papillary, papillary-follicular and combined (papillary+papillaryfollicular) variants in the age series of children-adolescents-adults remained unchanged(p<0.0001; p<0.0013; p<0.0001, respectively). A significant increasing linear age trend was
also noted for the frequency of fully encapsulated РТСs (p<0.0001, Table 5.7).
The selection had no effect on the invasive properties of radiogenic PTCs either (Table
4.8 of Chapter 4 and Table 5.7 of this Chapter). In the selected cases, significant decreasing
linear trends of frequency of intrathyroidal spread and extrathyroidal extension, vascularinvasion, regional and distant metastases in the age series of children-adolescents-adults
were also confirmed (all trends, p<0.0001).
Thus, our selection of cases by patients’ age and place of residence at the time of
the Chernobyl accident was not associated with significant changes in morphologicalcharacteristics of PTCs determined in corresponding age groups for the whole of Ukraine,
i.e. there was no detectable selection bias.
Considering the frequency of histological subtypes in sporadic PTCs (in patients bornafter the Chernobyl accident), it should be noted that the linear trends similar to those inradiogenic cancers were not found in age series (Tables 5.4, 5.5, 5.6) except for a decreasing
trend in the frequency of solid variant (p<0.0502, marginally). Analysis of encapsulated
PTCs also showed no age relationship (Table 5.7).
By contrast, invasive properties of sporadic (Table 5.7) as well as of radiogenic PTCs weresignificantly decreasing in the age series of children-adolescents-adults (intrathyroidal
extension, p<0.0470; extrathyroidal extension, p<0.0001; vascular invasion, p<0.0008;
regional metastases, p<0.0004, distant metastases to the lung, p<0.0106).
Conceivably, radiogenic and sporadic papillary carcinomas, when comparison is
performed in the age series, are characterized by the same trends for invasive features, butdisplay different character of distribution of main histological subtypes.
111

112

11
25
24
47
7
114

9.6
21.9
21.1
41.3
6.1
100

%
18
17
17
54
5
111

n
16.2
15.3
15.3
48.7
4.5
100

%
14
14
5
31
1
1
66

n
21.2
21.2
7.6
47.0
1.5
1.5
100

%
28
9
10
48
1
1
97

n
28.9
9.3
10.3
49.5
1.0
1.0
100

%

Adolescents 15-18 y.o. at surgery
Radiogenic
Sporadic

20
13
5
21
59

n
33.3
22.0
7.5
35.6
100

%

12
8
3
29
1
2
1
56

n

21.4
14.3
5.3
51.8
1.8
3.6
1.8
100

%

Adults 19-23 y.o. at surgery
Radiogenic
Sporadic

Papillary-follicular
Papillary-solid
Papillary-follicularsolid
Solid-follicular
Total

19.1
10.6
4.3

66.0
100

31
47

%

9
5
2

n

17
54

20
10
7

n

31.5
100

37.0
18.5
13.0

%

Children up to 14 y.o. at surgery
Radiogenic
Sporadic

9
31

13
8
1

n

29.0
100

41.9
25.8
3.2

%

15
48

19
8
6

n

31.2
100

39.6
16.7
12.5

%

Adolescents 15-18 y.o. at surgery
Radiogenic
Sporadic

6
21

12
3
-

n

28.6
100

57.1
14.3
-

%

12
29

7
6
4

n

41.4
100

24.1
20.7
13.8

%

Adults 19-23 y.o. at surgery
Radiogenic
Sporadic

Table 5.5
Structural combinations of mixed subtypes of PTC in patients born before (radiogenic) and after Chernobyl (sporadic cancers)

Classic papillary
Follicular
Solid
Mixed
Diffuse-sclerosing
Warthin-like
Cribriform
Total

n

Children up to 14 y.o. at surgery
Radiogenic
Sporadic

Table 5.4
Subtypes of PTC in patients born before (radiogenic) and after Chernobyl (sporadic cancers)

Chapter 5

48.2

17.5

55/114

20/114%%

38/111 34.2

34/111 30.6

n

27/66

14/66

n

40.9

21.2

%

47/97

25/97

n

48.5

25.8

%

Adolescents 15-18 y.o at surgery
Radiogenic
Sporadic

32/59

11/59

n

54.2

18.6

%

19/56

15/56

n

Intrathyroidal extension
Extrathyroidal extension
Multifocality
Vascular invasion
Regional metastases
Distant metastases
Fully encapsulated

85.1

66.7

6.1
85.1
67.5
23.8
5.3

76

7
97
77
27
6

%

97

n

11
79
71
14
22

60

74

n

9.9
71.2
64.0
12.6
19.8

54.1

66.7

%

Children up to 14 y.o at surgery
Radiogenic
Sporadic

7
44
35
9
10

30

35

n

10.6
66.7
53.0
13.6
15.2

45.0

53.0

%

11
64
54
6
15

40

61

n

11.3
66.0
55.7
6.2
15.5

41.2

62.9

%

Adolescents 15-18 y.o at surgery
Radiogenic
Sporadic

5
27
16
19

19

35

n

8.5
45.8
27.1
32.2

32.2

59.3

%

9
24
19
1
15

12

28

n

16.1
42.9
33.9
1.8
26.8

21.4

50.0

%

Adults 19-23 y.o at surgery
Radiogenic
Sporadic

33.9

26.8

%

Adults 19-23 y.o at surgery
Radiogenic
Sporadic

Table 5.7
Invasive proprties and tumor encapsulation in patients born before (radiogenic) and after Chernobyl (sporadic cancers)

Solid+Solid-Follicularvariants
Papillary+PapillaryFollicular variantsnChildren up to 14 y.o at surgery
Radiogenic
Sporadic

Table 5.6
PTCs with most prominent solid patterns (SV+SFV) and most prominent papillary patterns (PV+PFV) in patients born before(radiogenic) and after Chernobyl (sporadic cancers)

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

113

Chapter 5

Taking into account that earlier comparative analyses of PTC in children and adolescentsof Ukraine, Belarus, and Russia born before and after Chernobyl have not revealed substantial
morphological differences [10-14], in the present study we used deepened univariate andmultivariate statistical approaches to each of the three age-matched groups.
To compare pathological parameters between radiation-induced and sporadic PTC
by univariate analysis, Fisher exact test (FT) was used for categorical data, and two-tailed
Mann-Whitney test for quantitative measurements.
Univariate statistical analysis of main subtypes of PTC in children (Table 5.8) showedthat among radiogenic РТСs the frequency of tumors with solid-follicular strucuture (solid+ solid-follicular variants) was significantly higher than that in sporadic РТСs (p<0.009).
Conversely, the frequency of sporadic РТСs with papillary-follicular structure (papillary +papillary-follicular variants, p<0.006) was significantly higher than in radiogenic tumors.
Comparison of invasive features also revealed the most pronounced differences in childhoodgroups: radiogenic PTCs were characterized by a significantly higher frequency of intrathyroidal
extension (p<0.002), vascular invasion (p<0.015) and distant metastases (p<0.033).
In addition, in the group of children with radiogenic РТС, a significantly lower frequency
was observed for the fully encapsulated tumors as compared with sporadic РТСs (p<0.001),
and for the frequency of microcarcinomas sized up to 10 mm, but the difference is not quite
statistically significant (p<0.074). The groups of children with radiogenic and sporadic РТСsalso differed significantly in F:M ratio (p<0.026) as mentioned above.
Among adolescents and adults no significant differences between any of the above
parameters were observed (Table 5.8).
Multivariate analysis in each age group of patients was performed using standard
logistic regression modeling. The following variables were tested:
age at surgery (continuous; years);sex (categorical, M or F);
tumor size ≤10mm or >10 mm (categorical; yes or no);complete tumor capsule (categorical; yes or no);histological subtype (categorical; solid+solid follicular or other);lymph node metastases (categorical; yes or no);distant metastasis to the lung (categorical; yes or no);intrathyroidal spread (categorical; yes or no);extrathyroidal extension (categorical; yes or no);multifocality (categorical; yes or no);vascular invasion (categorical; yes or no).
Non-automatic backward elimination was applied to the full model that initially
included all the variables listed above. Once the most appropriate model was determined,
the maximum likelihood estimates of the respective parameters and their 95% confidence
intervals were calculated.
Multivariate logistic regression analysis (Table 5.9) confirmed significant differences
between radiogenic and sporadic PTCs in children. Four parameters (male gender, absenceof tumor capsule, solid+solid-follicular tumor architecture, and a higher frequency of
intrathyroidal spread) were found to be independently associated with radiogenic PTC. The
fifth parameter, the higher frequency of lymph node metastases, showed just marginalassociation with radiogenic PTCs.
114

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Table 5.8
Univariate statistical analysis of PTCs in patients born before (radiogenic) and after
Chernobyl (sporadic cancers) in age-matched groups
ChildrenParameters
Sex (M vs F)
Age at operation (years)
Tumor size (≤10 mm vs >10 mm)
Tumor capsule (yes vs no)
Subtype (solid+solid-follicular vs other)pN (pN1 vs pN0)
M (M1 vs M0)
Multifocality (yes vs no)
Intrathyroidal extension (yes vs no)
Extrathyroidal extension (yes vs no)
Vascular invasion (yes vs no)

OR
1.89
0.93
0.42
0.22
2.11
1.14
2.13
0.59
2.78
1.67
2.31

95% CI1.08-3.35
0.83-1.04
0.16-1.07
0.09-0.58
1.22-3.64
0.66-1.99
1.06-4.42
0.21-1.56
1.47-5.43
0.97-2.88
1.97-4.47

p-value
0.026
0.190
0.074
0.001
0.009
> 0.5
0.033
0.287
0.002
0.063
0.015

OR
1.44
1.01
0.69
0.92
0.78
0.92
2.42
0.94
0.69
1.21
1.03

95% CI
0.73-2.86
0.76-1.33
0.29-1.64
0.38-2.14
0.37-1.63
0.49-1.72
0.83-7.56
0.33-2.52
0.36-1.29
0.64-2.27
0.53-2.00

p-value
0.379
> 0.5
0.394
> 0.5
> 0.5
> 0.5
0.106
> 0.5
0.241
> 0.5
> 0.5

OR
1.57
1.28
0.94
1.30
0.63
0.72
0.48
1.46
1.74
1.12

95% CI
0.64-3.96
0.96-1.73
0.34-2.53
0.58-2.94
0.26-1.51
0.32-1.61
0.14-1.50
0.70-3.07
0.76-4.12
0.54-2.35

p-value
0.324
0.097
> 0.5
> 0.5
0.374
0.427
0.211
0.315
0.191
> 0.5

AdolescentsParameters
Sex (M vs F)
Age at operation (years)
Tumor size (≤10 mm vs >10 mm)
Tumor capsule (yes vs no)
Subtype (solid+solid-follicular vs other)pN (pN1 vs pN0)
M (M1 vs M0)
Multifocality (yes vs no)
Intrathyroidal extension (yes vs no)
Extrathyroidal extension (yes vs no)
Vascular invasion (yes vs no)

AdultsParameters
Sex (M vs F)
Age at operation (years)
Tumor size (≤10 mm vs >10 mm)
Tumor capsule (yes vs no)
Subtype (solid+solid-follicular vs other)pN (pN1 vs pN0)
Multifocality (yes vs no)
Intrathyroidal extension (yes vs no)
Extrathyroidal extension (yes vs no)
Vascular invasion (yes vs no)115

Chapter 5

Table 5.9
Results of multivariate statistical analysis of PTC in patients born before (radiogenic) andafter Chernobyl (sporadic cancers) in age-matched groups
ChildrenParameters
Sex (M vs F)
Tumor capsule (yes vs no)
Subtype (solid+solid-follicular vs other)pN (yes vs no)
Intrathyroidal spread (yes vs no)

OR
1.86
0.27
1.89
1.89
2.80

95% CI
1.02-3.43
0.09-0.73
1.05-3.33
0.96-3.70
1.36-5.98

p-value
0.042
0.009
0.031
0.064
0.005

OR
3.00

95% CI
1.07-9.91

p-value
0.037

OR
1.49
0.34
0.32
3.56

95% CI1.08-2.12
0.11-0.93
0.08-1.05
1.25-1.51

p-value
0.014
0.034
0.060
0.017

AdolescentsParameters
Extrathyroidal extension (yes vs no)

AdultsParameters
Age at operation (older vs younger)pN (yes vs no)
Multifocality (yes vs no)
Extrathyroidal extension (yes vs no)

In adolescents, only a higher chance of extrathyroidal extension in radiogenic РТСs wasnoted. In adults, the logistic regression revealed a significant association for four parameters:
age at surgery, lymph node metastases, and extrathyroidal extension. A higher frequencyof extrathyroidal extension was associated with radiogenic РТСs. On the contrary, a higher
frequency of lymph node metastases, younger age and higher frequency of multifocality(marginally) were associated with sporadic РТСs (Table 5.9). Of note, univariate statisticalanalysis showed no significant differences for any of these parameters in adolescents andadults.
Thus, radiogenic papillary carcinomas in each of the age-matched groups had certain
differences from sporadic ones. The most pronounced differences were observed in agematched groups of children; these were confirmed on both univariate and multivariate
statistical analyses.
The data obtained suggest that after radiation exposure at the age 0-4 years old,the most rapidly progressing towards clinical manifestations PTCs (latency in subjects
operated on in childhood ranged from 3.8 to 13.8 years, mean 9.4 years, Table 5.10) wereindependently associated with the solid and/or solid-follicular growth pattern, absenceof tumor capsule, and such an aggressive morphological feature as intrathyroidal spreadas compared to sporadic PTCs in the age-matched group. It should be noted that thehigher aggressiveness of radiogenic Chernobyl papillary carcinomas in children of Ukraine
and Belarus with a shorter latency was associated with the presence of a marked solid
component, as reported in our previous study [15].
116Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Apparently, the slower development of radiogenic tumors in adolescents and adults(mean latency 14.4 and 18.8 years, respectively, Table 5.10) levels off the differences inhistological architectonics seen in children. On multivariate analysis, associations were
found only for the greater chance of extrathyroidal extension in adolescents and adults
and also for the lower chance of nodal disease in adults, but no correlation was found withtumor morphology in these age groups.
It is worth noting that such a “convergence” of morphological characteristics between
radiogenic and sporadic PTCs with increasing patients’ age and, naturally, the latencyof radiogenic tumors, could perhaps be explained, at least in part, by different thyroid
doses received during the Chernobyl accident by children at surgery on one hand, andadolescents and/or adults at surgery on the other. This hypothesis is based on the resultsof our cohort studies obtained within the Ukrainian-American Project [16]. It was shownthat after the 1st screening during the period 1998 to 2000 (mean latency 14.6 years), thenumber of thyroid cancer cases per 1000 cohort members was the highest (10.2/1000) in
the high-dose group in which thyroid doses were more than 1 Gy as compared with the
low-dose group with thyroid doses less than 0.3 Gy (1.3/1000, p<0.0001). By contrast, after
the 4th screening during 2006-08 (mean latency 20.9 years), such tendency was no longer
observed (1.2/1000 and 1.5/1000 respectively, p<0.753). It therefore seems possible thatthe rapid progression of radiogenic PTCs in children at surgery might be associated withhigher exposure doses as compared with radiogenic tumors in adolescents and adults
which are characterized by the longer latency.
To verify this supposition, we analyzed individual reconstructed 131I thyroid doses in allcases of radiogenic PTCs which have been calculated by a method described in a recent
article [17] and in Chapter 2 of this monograph for thyroid tumors included in the Chernobyl
Tissue Bank (CTB). Mean 131I thyroid dose in our cohort which included 239 children aged 0
to 4 years at exposure was 1.016 Gy (95% CI 0.701-1.332; median 0.336 Gy; minimum 0.040
Gy; maximum 24.110 Gy).
In the comparison of three age groups with different latency by the Kruskal-Wallis
nonparametric ANOVA, no significant differences between exposure doses were found.
Although the median of doses was somewhat decreasing in the series children-adolescentsadults, no significant linear trend was found (Table 5.10). A plausible explanation of theabsence of significant differences between thyroid doses would be that all UkrainianAmerican cohort members had direct measurements of thyroid activity (see Chapter 2)
unlike patients in the present study, who had direct measurements of thyroid activity onlyin 16.3% cases (39 out of 239). The accuracy of dose estimates in the Ukrainian-Americancohort was obviously higher with narrower CI range. In addition, patients distributions by
age at the time of Chernobyl (0 to 4 years) and at surgery (4 to 23 years) differed significantly
from those included in the Ukrainian-American project [16,18,19] in which the age at
exposure exceeded 4 years in most cases, there were practically no patients operated inchildhood, and the age of operated adults reached 34 years.
A more detailed analysis of mean thyroid doses for those pathological parameters that
distinguished radiogenic PTCs from sporadic ones showed that doses were significantly
higher in children/Females comparing with adults/Females. When comparing the doses offemales and males, those were higher for males in all age groups, especially in adolescentsand adults, but without significant difference (Table 5.11).
117

Chapter 5

Analysis of dose relationship with РТС size (microcarcinoma vs other) demonstrated
different trends in children, adolescents and adults. While in children the mean dose
for microcarcinomas was insignificantly lower than in PTCs of larger size, in adolescentsand adults microcarcinoma was associated with higher doses, and in adolescents such a
difference was significant (Table 5.12).
In patients of all age groups with non-encapsulated РТС mean doses were higher thanin patients with fully encapsulated tumor (Table 5.13), but significant differences were notfound either in children in whom this parameter was strongly associated with radiogenic
cancer, or in older patients in whom this association was absent.
For the combined solid + solid-follicular subtypes of РТС, which were associated withradiogenic cancer in children, mean doses did not display statistically significant differences
either in the series children-adolescents-adults or when the doses were compared to those
for all other subtypes of РТС (Table 5.14).
Morphological features of tumor agressiveness (intrathyroidal spread, extrathyroidal
extension, nodal disease), were not associated with significant differences in mean doses
in all age groups either. Also, no dose differences were found in patients with or withoutmorphological manifestations of agressiveness (Tables 5.15-5.17). A significantly higher
exposure dose was noted only in adolescents without intrathyroidal spread as comparedto patients with such or with corresponding adults (Table 5.15).
Tumor multifocality, which was marginally associated with sporadic PTC in adults,
was associated in radiogenic carcinomas of this age group with a higher (comparedwith children and adolescents) exposure dose (Table 5.18) but no significance could be
expected taking into account the range of dose estimates from 0.155 to 12.279 Gy in 5
observations.
Table 5.10
Latency and thyroid radiation doses in patients with radiogenic PTC(born before Chernobyl)
Latency (years)
Parameters
Children
Adolescents
Adults(n=114)(n=66)(n=59)
Mean
9.4
14.8
18.9
95 % CI
9.0-9.9
14.3-15.2
18.3-19.4
Minimum
3.8
11.7
14.8
Median
9.4
14.4
18.8
Maximum
13.8
17.9
22.6
p-value<0.0001
p-trend<0.0001a<0.0001
p-valuep-value<0.0001 b<0.0001 ca- children vs adolescents;

118b

Children(n=114)0.995
0.591-1.398
0.048
0.406
16.584

Doses (Gy)
Adolescents(n=66)
1.333
0.487-2.179
0.040
0.341
24.1100.801 a0.098 b0.182 c- children vs adults; c - adolescents vs adults

Adults(n=59)
0.704
0.269-1.139
0.044
0.261
12.2800.226
0.467

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Table 5.11
Thyroid radiation doses in females and males with radiogenic PTC(born before Chernobyl)
Females, doses, Gy

Males, doses, Gy

MeanChildren(n=68)
1.023

Adolescents
Adults(n=44)(n=44)
0.962
0.459

95 % CI

0.970-1.476

0.320-1.607

0.275-0.714 0.187-1.721 0.208-4.359

0.379-3.014

Minimum

0.048

0.040

0.044

0.057

0.068

0.101

Median

0.459

0.327

0.240

0.329

0.366

0.434

Maximum

13.21613.286

3.175

16.58424.11012.279Parametersp-valueChildren(n=46)
0.953

Adolescents
Adults(n=22)(n=15)
2.075
1.317

0.046

p-trend

0.551

0.113

p-value

0.235

p-value0.015 b

0.472
0.234

a

0.295

d

e

0.139 f0.217 c- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: female
vs male; e - adolescents: female vs male; f - adults: female vs male;a

Table 5.12
Thyroid radiation doses and tumor size in patients with radiogenic PTC(born before Chernobyl)
Size ≤10 mm, doses, Gy

Size ≥11 mm, doses, Gy

MeanChildren
(n=7)
0.396

Adolescents
Adults(n=14)(n=13)
4.323
1.380

95 % CI

0.179-0.612

0.473-8.174

0.620-3.380 0.605-1.464 0.310-0.746

0.304-0.722

Minimum

0.152

0.203

0.087

0.048

0.070

0.044

Median

0.342

2.136

0.274

0.416

0.299

0.259

Maximum

0.715

24.11012.27916.584

4.508

3.175

Parametersp-value

Adolescents
Adults(n=52)(n=46)
0.528
0.513

0.022

p-trend

0.115

0.664

p-value

0.025

ap-value

0.757bp-valueChildren(n=107)
1.034

0.084
0.102

0.017

c

a

0.086 b0.798 c0.645 d0.0006 e

0.905 f- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: ≤10 mm
vs ≥11 mm; e – adolescents: ≤10 mm vs ≥11 mm; f - adults: ≤10 mm vs ≥11 mma

119

Chapter 5

Table 5.13
Thyroid radiation doses and full tumor encapsulation in patients with radiogenic PTC(born before Chernobyl)
Fully encapsulated, doses, Gy

MeanChildren
(n=6)
0.327

95 % CI

0.126-0.527 0.092-1.315 0.161-0.563 0.607-1.457 0471-2.454

0.229-1.504

Minimum

0.083

0.087

0.044

0.048

0.040

0.087

Median

0.402

0.327

0.202

0.406

0.359

0.285

Maximum

0.540

3.400

1.626

16.58424.11012.279Parameters

Adolescents
Adults(n=10)(n=19)
0.612
0.362

Non- and partly encapsulated, doses, GyChildren(n=108)1.032

Adolescents(n=56)
1.462

Adults(n=40)
0.866

p-value

0.424

0.732

p-trend

0.534

0.737

p-value

0.635 ap-value

0.849 b0.842 a0.344 cp-value

0.412 b0.642 c0.348 d0.838 e0.089 f- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: full
encapsulation vs other; e – adolescents: full encapsulation vs other; f - adults: full encapsulationvs othera

Table 5.14
Thyroid radiation doses and combined Solid+Solid-Follicular subtype of PTC in patientsborn before Chernobyl
Solid+Solid-Follicular subtype, doses, GyChildrenParameters(n=55)
Mean
0.752

Other subtypes, doses, Gy

AdolescentsChildren
Adults (n=11)(n=14)(n=59)
0.730
0.716
1.222

Adolescents
Adults(n=52)(n=48)
1.496
0.701

95 % CI

0.433-1.071 0.315-1.144

0.107-1.325

0.494-1.951 0.424-2.558 0.177-1.226

Minimum

0.056

0.089

0.045

0.048

0.040

0.044

Median

0.369

0.352

0.285

0.428

0.327

0.254

Maximum

6.880

2.160

3.015

16.58424.11012.279p-value

0.855

0.134

p-trend

0.920

0.366

p-value

0.591 ap-value0.911bp-value

0.417 a0.966 c0.052 b0.212 c0.387 d0.814 e0.654 f- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: SV+SFV vsother; e – adolescents: SV+SFV vs other; f - adults: SV+SFV vs othera120

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Table 5.15
Thyroid radiation doses and intrathyroidal spread in patients with radiogenic PTC(born before Chernobyl)
Intrathyroidal spread, doses, Gy

MeanChildren(n=97)
0.973

95 % CI

0.573-1.373 0.268-1.021

0.116-1.540 0.486-2.729 0.349-3.873 0.213-0.959

Minimum

0.048

0.040

0.045

0.096

0.072

0.044

Median

0.453

0.292

0.285

0.316

0.428

0.235

Maximum

16.5844.595

12.27913.21624.1103.175

Parameters

Adolescents
Adults(n=35)(n=35)
0.644
0.828

No intrathyroidal spread, doses, Gy

p-value

0.238

p-trend0.692

p-value

0.120ap-value

0.289 bChildren(n=17)
1.121

Adolescents
Adults(n=31)(n=21)
2.111
0.523

0.067
0.196 a0.725 cp-value

0.308 b0.028 c0.436 d0.039 e0.436 f- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: intrathyroidal
spread, yes vs no; e – adolescents: intrathyroidal spread, yes vs no; f - adults: intrathyroidal spread,yes vs noa

Table 5.16
Thyroid radiation doses and extrathyroidal extension in patients with radiogenic PTC(born before Chernobyl)
Extrathyroidal extension, doses, Gy
Parameters
Mean
95 % CI
Minimum
MedianMaximum
p-valuep-trendp-valuep-valuep-valueChildren(n=76)
0.786
0.508-1.063
0.048
0.410
6.880

Adolescents(n=30)
0.726
0.281-1.171
0.046
0.330
5.167

0.646a0.372 b0.594

cAdults(n=19)
0.601
0.204-0.997
0.045
0.285
3.015
0.456
0.534

No extrathyroidal extension, doses, GyChildren(n=38)
1.413
0.314-2.513
0.065
0.396
16.5840.987a0.150 b0.648 dAdolescents
Adults(n=36)(n=40)
1.839
0.753
0.318-3.361 0.128-1.378
0.040
0.044
0.341
0.259
24.11012.2790.262
0.391
0.175 c0.541 e0.928 f- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: extrathyroidal
extension, yes vs no; e – adolescents: extrathyroidal extension, yes vs no; f - adults: extrathyroidal
extension, yes vs noa

121Chapter 5

Table 5.17
Thyroid radiation doses and lymph node metastases in patients with radiogenic PTC(born before Chernobyl)
Lymph node metastases, doses, Gy

No lymph node metastases, doses, Gy

MeanChildren(n=77)
0.983

Children(n=37)
1.020

95 % CI

0.560-1.407 0.294-1.090

0.149-1.135 0.106-1.934 0.296-3.819 0.148-1.306

Minimum

0.048

0.040

0.045

0.065

0.072

0.044

Median

0.416

0.251

0.247

0.397

0.390

0.261

Maximum

13.216

5.167

3.175

16.58424.11012.279Parameters

Adolescents
Adults(n=35)(n=16)
0.692
0.642

p-value

Adolescents
Adults(n=31)(n=43)
2.057
0.727

0.176

p-trend

0.107

0.570

p-value

0.117

p-value

0.186 b

0.200
0.245

a

a

0.855 cp-value

0.463 b0.028c0.616 d0.021 e0.658 fa
- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: lymph nodemetastases, yes vs no; e – adolescents: lymph node metastases, yes vs no; f - adults: lymph nodemetastases, yes vs no

Table 5.18
Thyroid radiation doses and multifocality in patients with radiogenic PTC(born before Chernobyl)
Multifocality, doses, Gy

No multifocality, doses, Gy

MeanChildren
(n=7)
0.496

95 % CI

0.172-0.821 -0.632-2.409-3.889-9.361

0.598-1.459 0.448-2.324

0.324-0.703

Minimum

0.150

0.089

0.155

0.048

0.040

0/044

Median

0.457

0.251

0.403

0.397

0.350

0.254

Maximum

1.056

4.595

12.27916.58424.1103.175

Parameters

AdolescentsChildren
Adults (n=5)(n=7)(n=107)
0.888
2.736
1.027

p-value

0.642

p-trend

0.145

0.200

p-value

0.535

p-value>0.999p-value

Adolescents
Adults(n=59)(n=54)
1.386
0.515

0.213
0.937

a

a

b

0.432

c

0.070 b0.093 c0.944d0.499e0.289 f- children vs adolescents; b - children vs adults; c - adolescents vs adults; d - children: multifocality,
yes vs no; e – adolescents: multifocality, yes vs no; f - adults: multifocality, yes vs noa

122Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Given mean thyroid doses in patients of three age groups with radiogenic papillarycarcinomas did not differ significantly for virtually all morphological characteristics understudy, we performed an additional deepened analysis of the dose-response relationship.
Those pathological parameters that appeared to be significant on the multivariate
analysis of radiation-induced vs sporadic PTCs were examined for their association withthyroid dose using univariate and multivariate standard logistic regression modeling:where a – a pathological parameter and z is:for the univariate analysis
z = Const + OR( D j )where Const is a constant, OR(Di) is the Odds Ratio for the dose group Di (i=0, .. , 4),relative to the dose group D0 with the OR=1 (referent group). All exposed patients were
subdivided in quartiles thereby determining the dose range for each quartile;
for the multivariate analysis:z = Const + b P k+ OR( D j )where Const is a constant, Pk – pathological parameters, OR(Dj) is the Odds Ratio for thedose group Dj relative to the dose group D0 with the OR=1 (referent group);
Two types of logistic regression models were applied:•• patients were stratified by eight dose intervals (i=0, .. ,8);•• a threshold dose model (two dose intervals) was used for which the reference doseinterval was determined by optimizing the model according to binomial maximum
likelihood.
The following pathological parameters (Pk) were tested for the multivariate analysis:age at surgery (continuous; years); sex (categorical, M or F); tumor size ≤10 mm or >10mm (categorical; yes or no); complete tumor capsule (categorical; no or yes); histologicalsubtype (categorical; solid+solid follicular or other); lymph node metastases (categorical;
yes or no); distant metastasis to the lung (categorical; yes or no); intrathyroidal spread(categorical; yes or no); extrathyroidal extension (categorical; yes or no); multifocality(categorical; yes or no).
The linear or linear-quadratic terms for the dose were forcedly introduced as independent
variable(s) in addition to the parameters used for the multivariate analysis of radiationinduced vs. sporadic PTCs.
EPICURE software package was used for the analysis. Non-automatic backwardelimination was applied to the full model that initially included all the variables listed
above. The binomial maximum likelihood estimates and the likelihood-based 95% CI
were calculated for parameters of all the above-introduced models. Likelihood ratio
statistics were used to calculate p-values for the studied effects and to test the statisticalsignificance of the respective parameters. The results of these analyses are presented
in Tables 5.19-5.21.
In children, the following pathological parameters were significantly different between
radiation-induced and sporadic PTCs: absence of full tumor capsule, histological subtype(solid + solid-follicular vs other), intrathyroidal spread (yes vs no), and lymph nodemetastases (yes vs no), marginally (Table 5.19).
123

Chapter 5

Table 5.19
Univariate and multivariate statistical analyses of association of different pathologicalparameters in exposed children
Tumor capsule, children
ParametersORp-value

95% CI

univariate
Thyroid dose (Gy)
< 0.1885

1.00

referent-

0.1885 - < 0.387

0.46

0.02-5.12> 0.5

0. 387 - < 0.7923

1.50

0.23-12.1> 0.5

0.7923 – 16.584

NA a

NA

NA

p-trend linear regression> 0.5 bmultivariate, stratified

Extrathyroidal extension

0.03

0.00-0.26< 0.001 c< 0.110

1.00

referent-

0.110 - < 0.185

NANA

0.185 - < 0.274

NANA

0.274 - < 0.406

0.26

0.01-4.32

0.37

0.406 - < 0.547

1.48

0.12-20.9> 0.5

0.547 - < 0.851

NANA

0.851 - < 1.907

NANA

1.907 –

NA

NA

Thyroid dose (Gy)linear dose model p-trend

0.1 b
multivariate, dose threshold

Extrathyroidal extension

0.06

0.00-0.43

0.004 c

< 0.110

1.00

referent-≥ 0.1100.13

0.13-1.21

0.07 bThyroid dose (Gy)there were no or too few cases in the given dose range to fit the model; b indicates non-significant
association of full tumor encapsulation with thyroid dose; c indicates significantly decreased chanceof fully encapsulated tumors among cases with extrathyroidal extensiona124Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Continuation of Table 5.19

Histological subtype, children
Parameters

OR

95% CI

p-value

univariate
Thyroid dose (Gy)
< 0.1885

1.00

referent-

0.1885 - < 0.387

1.64

0.58-4.76

0.35

0.387 - < 0.7923

1.24

0.44-3.58> 0.5

0.7923 – 16.584

2.06

0.72-6.12

0.18

p-trend linear regression> 0.5 amultivariate, stratified

Extrathyroidal extension

0.23

0.09-0.54< 0.001 b< 0.110

1.00

referent-

0.110 - < 0.185

1.22

0.26-5.94> 0.5

0.185 - < 0.274

0.97

0.20-4.80> 0.5

0.274 - < 0.406

1.88

0.40-9.22

0.42

0.406 - < 0.547

1.37

0.29-6.60> 0.5

0.547 - < 0.851

0.80

0.16-3.81> 0.5

0.851 - < 1.907

5.07

1.00-31.89

0.05

1.907 –

1.22

0.25-5.94> 0.5

Thyroid dose (Gy)linear dose model p-trend

0.1 a
multivariate, dose threshold

Extrathyroidal extension

0.24

0.10-0.56

0.002 b< 0.851

1.00

referent-≥ 0.851

2.03

0.81-5.23

0.31 aThyroid dose (Gy)indicates non-significant association of histological subtype (solid+solid-follicular) with thyroid
dose; b indicates significantly decreased chance of tumors with growth pattern other than solid or
solid-follicular among cases with extrathyroidal extensiona125Chapter 5

Continuation of Table 5.19

Intrathyroidal spread, children
Parameters

OR

95% CI

p-value

univariate
Thyroid dose (Gy)
< 0.1885

1.00

referent-

0.1885 - < 0.387

0.38

0.07-1.54

0.18

0.387 - < 0.7923

0.58

0.11-2.61

0.48

0.7923 – 16.584

1.56

0.24-12.61> 0.5

p-trend linear regression

0.43 amultivariate, stratified

pT

8.48

2.05-43.28

0.003 bpN

7.96

1.90-41.07

0.004 c

< 0.110

1.00

referent-

0.110 - < 0.185

0.96

0.03-20.62

0.185 - < 0.274

0.78

0.03-13.42

0.274 - < 0.406

0.21

0.01-3.97

0.37

0.406 - < 0.547

0.68

0.02-11.27> 0.5

0.547 - < 0.851

1.56

0.05-31.79

0.851 - < 1.907

3.33

0.08-160.1

1.907 –

1.52

0.04-54.32

Thyroid dose (Gy)linear dose model p-trend

0.1 a
multivariate, dose threshold

pT

8.21

2.27-34.17

0.001 bpN

6.54

1.73-28.86

0.001 c

< 0.547

1.00

referent-≥ 0.5472.80

0.71-13.57

0.147 aThyroid dose (Gy)indicates non-significant association of intrathyroidal spread with thyroid dose; b indicatessignificantly increased chance of intrathyroidal spread among tumors with advanced pT category;cindicates significantly increased chance of intrathyroidal spread among cases featuring lymph
node metastasesa126Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Continuation of Table 5.19

Lymph node metastases, children
Parameters

95% CI

p-valuereferent
0.24-2.33
0.24-2.33
0.27-2.65

> 0.5
> 0.5
> 0.5
> 0.5 a1.03-9.55
0.01-0.84
1.00-31.23
0.01-0.21

0.042 b0.034 c0.049 d0.004 e1.00
1.48

referent
0.20-10.8

> 0.5

0.89

0.15-5.42

> 0.5

2.21

0.26-18.37

0.45

2.15

0.29-16.09

0.46

0.81

0.15-4.44

> 0.5

0.58

0.10-3.49

> 0.5

2.26

0.31-16.42

0.42

OR
univariate

Thyroid dose (Gy)
< 0.1885
0.1885 - < 0.387
0.387 - < 0.7923
0.7923 – 16.584
p-trend linear regression
Sex
Tumor capsule
M
Vascular invasion
Thyroid dose (Gy)
< 0.1100.110 - < 0.185
0.185 - < 0.274
0.274 - < 0.406
0.406 - < 0.547
0.547 - < 0.851
0.851 - < 1.907
1.907 –

1.00
0.76
0.76
0.84
multivariate, stratified
2.95
0.11
4.36
0.05

linear dose model p-trend> 0.5 amultivariate, dose threshold

Sex

2.89

1.05-9.33

0.041 bTumor capsule

0.15

0.01-0.93

0.036 cM

4.41

1.00-28.41

0.048 dVascular invasion

0.05

0.01-0.20< 0.001 e< 0.110

1.00

referent-≥ 0.1101.56

0.44-4.27

0.72 aThyroid dose (Gy)aindicates non-significant association of lymph node metastases with thyroid dose; b indicatessignificantly higher chance of lymph node metastasis in males; c indicates significantly decreased
chance of lymph node metastases among cases with fully encapsulated tumor; d indicates significantly
increased chance of lymph node metastases among cases with distant metastases; e indicatessignificantly decreased chance of lymph node metastases among cases without vascular invasion

127

Chapter 5

In adolescents, only one pathological parameter was significantly different between
radiation-induced and sporadic PTCs: extrathyroidal extension (yes vs no) (Table 5.20).
Table 5.20
Univariate and multivariate statistical analyses of association of extrathyroidal extension
in exposed adolescentsParameters

OR

95% CI

p-valuereferent
0.17-2.77
0.36-5.81
0.10-1.88

> 0.5
> 0.5
0.28
0.19 aunivariate
Thyroid dose (Gy)
< 0.1938
0. 1938 - < 0.341
0.341 - < 0.802
0.802 – 24.11
p-trend linear regression
pN
Vascular invasion
Thyroid dose (Gy)
< 0.095
0.095 - < 0.194
0.194 - < 0.264
0.264 - < 0.341
0.341 - < 0.425
0.425 - < 0.802
0.802 - < 2.449
2.449 –
linear dose model p-trend
pN
Vascular invasion
Thyroid dose (Gy)
< 0.194≥ 0.194

1.00
0.70
1.43
0.45

multivariate, stratified
7.18
1.76-39.45
0.11
0.02-0.47

0.005 b0.002 c

1.00
0.61
1.54

referent-

0.05-6.20
0.13-20.72

> 0.5
> 0.5

0.74
2.19
3.42
0.47
0.67

0.05-8.96
0.17-32.21
0.28-49.84
0.04-5.06
0.04-10.43

0.49
> 0.5
> 0.5
0.42
0.37
> 0.5 amultivariate, dose threshold
7.18 b
1.76-39.45c
0.11
0.02-0.47
1.00
1.88

referent
0.08-23.17

0.005 b0.002 c0.52 aindicates non-significant association of extrathyroidal extension with thyroid dose; b indicatessignificantly increased chance of extrathyroidal extension among cases with lymph node metastases;cindicates significantly decreased chance of extrathyroidal extension among cases without vascularinvasiona

In adults, the following pathological parameters were significantly different between
radiation-induced and sporadic PTCs: extrathyroidal extension (yes vs no), lymph nodemetastases (yes vs no), and multifocality (yes vs no, marginally) (Table 5.21).
128

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Table 5.21
Univariate and multivariate statistical analyses of association of different pathologicalparameters in exposed adults
Lymph node metastases, adults
Parameters

OR

95% CI

p-value

univariate
Thyroid dose (Gy)
< 0.160

1.00

referent-

0. 160 - < 0.261

0.55

0.09-2.82

0.47

0.261 - < 0.560

0.73

0.14-3.51> 0.5

0.560 - 12.28

0.74

0.15-3.52> 0.5

p-trend linear regression> 0.5 amultivariate, stratified

Sex

0.05

0.02-0.53

0.044 bTumor capsule

0.01

0.00-0.22

0.034 cVascular invasion

0.02

0.00-0.17< 0.001 d

Thyroid dose (Gy)
< 0.102

1.00

referent-

0.102 - < 0.155

0.03

0.00-1.79

0.13

0.155 - < 0.202

0.20

0.00-5.35

0.35

0.202 - < 0.261

0.01

0.00-0.20

0.012

0.261 - < 0.396

0.13

0.00-2.44

0.19

0.396 - < 0.562

0.04

0.00-1.54

0.13

0.562 - < 1.260

0.01

0.00-0.21

0.013

1.260 –

0.12

0.00-3.04

0.23

linear dose model p-trend
Sex> 0.5 amultivariate, dose threshold
0.06
0.03-0.51

0.042 bTumor capsule

0.01

0.00-0.21

0.036 cVascular invasion

0.02

0.00-0.18< 0.001 d< 0.102

1.00

referent-≥ 0.1020.08

0.00-1.88

0.14 aThyroid dose (Gy)indicates non-significant association of lymph node metastases with thyroid dose; b indicatessignificantly decreased chance of lymph node metastasis in males; c indicates significantly decreased
chance of lymph node metastases in cases of fully encapsulated tumors; d indicates significantly
decreased chance of lymph node metastases among cases without vascular invasiona129

Chapter 5

Continuation of Table 5.21
Multifocality, adults
Parameters

OR

95% CI

p-value

univariate
Thyroid dose (Gy)
< 0.160

1.00

referent-

0. 160 - < 0.261

NA a

NA

NA

0.261 - < 0.560

3.50

0.34-75.98

0.27

0.560 – 12.28

1.00

0.04-26.97> 0.5

p-trend linear regression

0.12 bmultivariate, stratified

Tumor size

0.10

0.01-0.69

0.021 c

< 0.110

1.00

referent-

0.110 - < 0.185

NA

NA

> 0.5

0.185 - < 0.274

NA

NA

> 0.5

0.274 - < 0.406

NA

NA

> 0.5

0.406 - < 0.547

NA

NA

> 0.5

0.547 - < 0.851

NA

NA

> 0.5

0.851 - < 1.907

NA

NA

> 0.5

1.907 –

NA

NA

> 0.5

Thyroid dose (Gy)Linear/quadratic dose model p-trend

0.11 bmultivariate, dose threshold
Tumor size

0.10

0.01-0.69

0.026 c

< 0.406

1.00

referent-≥ 0.406

4.05

0.49-87.00

0.20 bThyroid dose (Gy)there were no or too few cases in the given dose range to fit the model; b indicates non-significant
association of multifocality with thyroid dose; c indicates significantly decreased chance ofmultifocality among small tumorsa130Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

Continuation of Table 5.21
Extrathyroidal extension, adults
Parameters

OR

95% CI

p-value

univariate
Thyroid dose (Gy)
< 0.160

1.00

referent-

0. 160 - < 0.261

0.80

0.16-3.91> 0.5

0.261 - < 0.560

1.00

0.21-4.68> 0.5

0.560 – 12.28

1.00

0.20-4.66> 0.5

p-trend linear regression> 0.5 amultivariate, stratified

Tumor capsule

0.05

0.00-0.37

0.002 b

Vascular invasion

0.08

0.01-0.36< 0.001 c

1.00

referent-

Thyroid dose (Gy)
< 0.1020.102 - < 0.155

0.78

0.02-24.50> 0.5

0.155 - < 0.202

0.57

0.03-11.74> 0.5

0.202 - < 0.261

0.23

0.01-4.56

0.32

0.261 - < 0.396

0.51

0.02-9.09> 0.5

0.396 - < 0.562

0.56

0.03-10.18> 0.5

0.562 - < 1.260

0.15

0.00-3.24

0.23

1.260 –

0.32

0.02-6.00

0.44

linear dose model p-trend> 0.5 amultivariate, dose threshold

Tumor capsule0.03 b

0.00-0.36

0.002 b

Vascular invasion

0.07

0.00-0.32< 0.001 c< 0.102

1.00

referent-≥ 0.1020.42

0.04-4.45

0.45 aThyroid dose (Gy)indicates non-significant association of extrathyroid extension with thyroid dose; b indicatessignificantly decreased chance of extrathyroid extension in encapsulated tumors; c indicatessignificantly decreased chance of extrathyroid extension among cases without vascular invasion.

aThus, as shown by the results of either univariate or any type of multivariate analysis(Tables 5.19-5.21), no evidence of significant association with thyroid dose was found forany pathological parameter tested in all age groups.

131Chapter 5

The only exception was a marginally significant association of the combined solid +solid-follicular subtype of РТС in children with the dose range from 0.851 to 1.907 Gy (Table
5.19), whose lower limit almost coincides with mean thyroid exposure dose (0.752 Gy) inchildren with these growth patterns (Table 5.14). In view of recently published results ofmolecular genetic study of PTCs identified in the Ukrainian-American cohort, which has
established a positive association between RET/PTC rearrangements and 131I thyroid dosewith an inflection point at 1.6 Gy [20], this fact draws attention. Notably, namely RET/
PTC rearrangements, RET/PTC3 in particular, are most common among children and areassociated with the solid and solid-follicular tumor structure [21, 22].
As a whole, radiogenic papillary carcinomas in children exposed after the Chernobyl
accident at the age under 4 years (mean 131I thyroid dose 1.016 Gy) and subdivided by theirage at surgery into three groups (children, adolescents and adults) significantly differed fromsporadic carcinomas in age-matched groups for a number of morphological parameters.
Univariate and multivariate statistical analyses revealed the most substantial differences
in both histoarchitectonics and invasive features of radiogenic PTCs, demonstrating theirmore aggressive behaviour especially well seen in age-matched groups of children. In
adolescents and adults, morphological differences between radiogenic and sporadic
tumors were found only for isolated parameters and those were revealed only bymultivariate analysis.
Such a “convergence” of morphological differences between radiogenic and sporadic
PTCs with increasing patients’ age (hence the latency of radiogenic tumors), was not
associated with the lower thyroid exposure dose or a certain dose range for mostmorphological manifestations of tumor agressiveness. A significant association was noted
only between solid + solid-follicular subtype and a dose range from 0.851 to 1.907 Gy inchildren, for which an association with RET/PTC rearrangements was recently reported [20].
It is quite possible that future molecular genetic investigations employing advanced
technologies, e.g next generation sequencing, will discover new genetic/epigenetic
alterations unknown at present that are associated with radiation thyroid carcinogenesis,
which, in turn, will allow better understanding of the mechanisms underlying more
pronounced morphological signs of aggressiveness of radiogenic PTCs with short latency.
Continuous ongoing verifications of thyroid doses in children and adolescents of
Ukraine after Chernobyl aimed at the reduction of uncertainties in dose estimates [23, 24]
are highly important for the subsequent analyses of dose-response relationship. These
would possibly allow establishing more confident associations between morphologicalparameters and exposure doses.

References
1. Likhtarev IA, Sobolev BG, Kairo IA, et al. Thyroid cancer in the Ukraine. Nature 1995;375:365.
2. Tronko MD, Bogdanova TI, Komissarenko IV, et al. Thyroid carcinoma in children and adolescentsin Ukraine after the Chernobyl accident: statistical data and clinicomorphologic characteristics.
Cancer 1999;86:149-156.

132

Comparative pathological analysis of papillary thyroid carcinoma in age-matched groups ....

3. Tronko M, Bogdanova T, Likhtarev I, et al. Thyroid gland and radiation (fundamental and applied
aspects): 20-years after the Chernobyl accident. Radiation Risk Perspectives; Shibata Y, Namba H,
eds. Amsterdam:Elsevier;2007:46-53.
4. Tronko M, Bogdanova T, Likhtarev I, et al. Thyroid cancer in Ukraine after the Chernobyl accident:
incidence, pathology, treatment, and molecular biology. Radiation health risk sciences; Nakashima
M, Takamura N, Tsukasaki K; eds. Tokio, Berlin, Heidelberg, New-York:Springer; 2009:305-316.
5. Tronko M, Bogdanova T, Komisarenko I, et al. Thyroid cancer in Ukraine after the Chernobyl
catastrophe: 25-year experience of follow-up. A challenge of radiation health risk management;
Nakashima M, Takamura N, Suzuki K, Yamashita S; eds. Nagasaki: Newspaper Publish; 2012:239244.
6. Likhtarev IA, Gulko GM, Kairo IA, et al. Thyroid doses resulting from the Ukraine Chernobyl
accident - Part I: Dose estimates for population of Kiev. Health Physics 1994; 66:137-146.
7. Jacob P, Goulko, Heidenreich WF, et al. Thyroid cancer risk to children calculated. Nature
1998;392:31-32.
8. Tronko ND, Bogdanova TI. Thyroid cancer in children and adolescents. Health effects of Chornobyl
accident; Vozianov A, Bebeshko V, Bazyka D; eds. Kyiv: DIA LTD;2003: 60-68.
9. Brenner AV, Tronko MD, Hatch M, et al. I-131 dose response for incident thyroid cancers in
Ukraine related to the Chornobyl accident. Environ Health Perspect 2011;19:933-939.
10. Bogdanova TI, Zurnadzhy LY, Greenebaum E, et al. A cohort study of thyroid cancer and otherthyroid diseases after the Chornobyl accident: pathology analysis of thyroid cancer cases in
Ukraine detected during the first screening (1998-2000). Cancer 2006;107:2559-2566.
11. LiVolsi VA, Abrosimov AA, Bogdanova T, et al. The Chernobyl Thyroid Cancer Experience:
Pathology. Clinical Oncology 2011;23:261-267.
12. Demidchik YuE, Demidchik EP, Saenko VA, et al. Childhood thyroid cancer in Belarus. Radiation
Risk Perspectives; Shibata Y, Namba H; eds. Amsterdam:Elsevier;2007:32-38.
13. Demidchik Yu, Fridman M, Schmid KV, et al. Papillary thyroid cancer in Childhood and adolescentswith specific consideration of patients after radiation exposure. Updates in the understanding
and management of thyroid cancer; Fahey TJ; ed. INTECH;2012:163-188.
14. Lushnikov EF, Tsyb AF, Yamashita Sh. Thyroid cancer in Russia after Chernobyl. Moscow:Meditsina
Publishing House; 2006.
15. Williams ED, Abrosimov A, Bogdanova T, et al. Thyroid carcinoma after Chernobyl latent period,
morphology and aggressiveness. Br. J. Cancer 2004;90:2219-2224.
16. Tronko M, Mabuchi M, Bogdanova T, et al. Thyroid cancer in Ukraine after the Chernobyl accident(in the framework of the Ukraine-US Thyroid Project). J. Radiol. Prot 2012:N65-N69.
17. Likhtarov I, Thomas G, Kovgan L, et al. Reconstruction of individual thyroid doses for Ukraine
subjects of the Chornobyl tissue bank. Radiat Prot Dosimetry 2013; Apr 17. [Epub ahead of print]
18. Tronko M, Howe G, Bogdanova T, et al. A cohort study of thyroid cancer and other thyroid
disease following the Chornobyl accident: thyroid cancer cases in Ukraine detected during firstscreening. J.Nat.Cancer Inst 2006;98:896-903.
19. Bogdanova TI, Zurnadzhy LY, Greenebaum E, et al. A cohort study of thyroid cancer and otherthyroid diseases after the Chornobyl accident: pathology analysis of thyroid cancer cases in
Ukraine detected during the first screening (1998-2000). Cancer 2006;107:2559-2566.
20. Leeman-Neill RJ, Brenner AV, Little MP, et al. RET/PTC and PAX8/PPARgamma chromosomal
rearrangements in post-Chernobyl thyroid cancer and their association with iodine-131
radiation dose and other characteristics Cancer, 2013;119:1792-1799.

133

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21. Thomas GA, Bunnell H, Cook HA, et al. High prevalence of RET/PTC rearrangements in Ukrainianand Belarussian post-Chernobyl thyroid papillary carcinomas: a strong correlation between
RET/PTC3 and the solid-follicular variant. The J Clin EndocrMetabolism 1999;84:4232-4238.
22. Santoro M, Thomas GA, Vecchio G, et al., Gene rearrangement and Chernobyl related thyroid
cancers. British journal of cancer 2000;82: 315-322.
23. Kukush A, Shklyar S, Masiuk S, et al. Methods for Estimation of Radiation Risk in EpidemiologicalStudies Accounting for Classical and Berkson Errors in Doses. Int J Biostatistics 2011;7:
http://www.bepress.com/ijb/vol7/iss1/15.
24. Likhtarov I, Masiuk S, Chepurny M, et al. Error estimation for direct measurements in May-June
1986 of 131I radioactivity in thyroid gland of children and adolescents and their registration inrisk analysis. Mathematics and Life Sciences; Antoniouk A, Melnik R; eds. Berlin, Boston:Walter deGruyter GmbH; 2013.

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Ukrainian contribution to the international Chernobyl Tissue Bank (CTB)

Chapter

6

GA Thomas, T Bogdanova, M Tronko,
S Yamashita

Ukrainian contribution to the international
Chernobyl Tissue Bank (CTB)

Cancer is an extremely complex disease that involves the interaction of biologicalpathways on a number of levels. Activation of the individual pathways does not necessarily
occur in an independent fashion through parallel linear routes, but operates through large
and complex networks of interacting pathways. Interactions between pathways can occur
at a number of different levels and can interact directly, e.g. via phosphorylation events orindirectly, e.g. via regulation of gene expression.
In addition to understanding the interaction of pathways within a cell, it is clear thatcancer cells do not exist within a vacuum. They respond to signals from outside of theindividual cell, between different types of cell within a tissue (e.g. epithelial cells responding
to signals generated from endothelial or stromal cells), and with stimuli external to the tissue,
e.g. hormones, etc. Therefore cancer can be considered to be an extremely complicatedsystem, one in which when one key node is blocked by use of an antineoplastic agent, forexample, has the opportunity to re-route the signaling to overcome the block.
Most cancer researchers use rather reductionist approaches and focus their studies
either on a particular gene of interest, or a particular pathway. The ability that we now havethrough the generation of “omics” data to provide data on multiple pathways simultaneouslymeans that we need a paradigm shift in cancer research. The ability to generate several
types of “omics” data from each individual cancer specimen will provide much more
information about the system in general. This necessitates the ability to provide analytes
of different types to be used in individual “omics” platforms to generate data on genome
sequence, DNA copy number, epigenomic, transcriptomic, proteomic, and metabolomic
data. The data then needs to be integrated to identify the key genes and pathways driving
an associated phenotype, such as drug response or clinical outcome.
Tissue banks may play a key role in this shift in our approach to the characterizationof cancer by not only supplying human biosamples to researchers using complimentary
technologies, but also providing a platform for the data on an individual patient to becollated and correlated with clinical information.
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Chapter 6

The Chernobyl Tissue Bank was established in 1998 and designed with a systems biology
approach to radiation-induced thyroid cancer in mind. This paper sets out the strategy
for the development of the CTB, and, in particular, the substantial contribution made by
Ukraine to its success.
The Chernobyl Tissue Bank – the paradigm for a cancer resource
designed for systems biology
The CTB has been funded by four sponsors (the National Cancer Institute of the US,
the European Commission (EC), the Sasakawa Memorial Health Foundation of Japan(SMHF) and the World Health Organization (WHO)) and is supported by two of thecountries most affected by fallout from the reactor accident, Ukraine and the RussianFederation.
In the early 1990s, a number of projects studying the effect of the Chernobyl accident
were funded by the four sponsors listed above. The increase in thyroid cancers in children
and adolescents in Belarus and Ukraine had been confirmed in a number of publications[1,2]. By 1995, it was becoming apparent that several European research groups were
unknowingly receiving material from the same patients for research, and that there werediscrepancies in the pathological diagnoses being applied to the same tumor. Subsequently,
a report to the EC confirmed that there had indeed been considerable overlap since 1995
among a number of EC-funded molecular biology projects [3]. It was then recognized thata cooperative tissue bank would reduce the duplication of research effort and provide
better scientific data on the health effects of the Chernobyl accident. Following agreementon the various protocols, the Chernobyl Tissue Bank officially started collecting material
on October 1, 1998. The full history and detail on the ethics and governance of the project
have already been published [4].
Study cohort
The CTB study cohort comprises all patients with thyroid carcinomas and cellularfollicular adenomas from the contaminated oblasts (the Russian and Ukrainian equivalentof a US state) of the Russian Federation (Bryansk, Kaluga, Tula, and Oryol) and Ukraine(Kiev, Kiev City, Cherkassy, Chernigov, Rovno, Zhitomyr) who were born on or after April
26, 1967 (i.e., aged under 19 years at the time of the Chernobyl accident) and operated
on or after the October 1, 1998. In addition, a number of cases have been collected fromother areas of Ukraine, relatively less contaminated by radioactive fallout. The collection
currently comprises 4,288 cases of thyroid cancer and cellular follicular adenoma frompatients who were under 19 years at the time of the Chernobyl accident; 2,267 of these arefrom Ukraine. Frozen material is available on 1,727 out of the 2,267 cases from Ukraine, andDNA and RNA has already been extracted from a quarter of these cases. Collection of blood
samples began in late 1999 and samples of serum and whole blood have been collectedfrom around 950 Ukrainian patients. One important feature of the project is that it alsocollects biosamples from patients resident in the areas of Ukraine and Russia exposed to136

Ukrainian contribution to the international Chernobyl Tissue Bank (CTB)

radioactive fallout, but who were not exposed to radioiodine, as they were born morethan 9 months after the accident. These cases form an age- and residency-matchedcohort of patients who develop spontaneous thyroid neoplasia. This is the ideal cohort forcomparison with those who were exposed to radioiodine in 1986. The current number ofcases in this valuable cohort is 379 (245 with a diagnosis of cancer, of which 124 are from
Ukraine). This number is much lower than those exposed to radioiodine – the incidence of
thyroid cancer being approximately the same as the background spontaneous rate fromuncontaminated regions – of the order of 1 per million per year.
The current project therefore consists of two banks of biological material and information
comprising:•• Snap frozen and formalin fixed, paraffin embedded samples from tumor, normal tissue
and, where possible, metastatic tissue from postoperative specimens,•• nucleic acids extracted from these specimens,•• vials of serum from patients whose thyroid tissue is held in the bank,•• samples of whole blood,•• DNA extracted from blood,•• Results from research projects supplied with samples from the CTB.
The Ukrainian contribution to the project represents 64% of the total.
Data management within the CTB
The data management infrastructure for the CTB was designed to facilitate a systems
biology approach to thyroid cancer. It comprises two separate databases, plus an integrated
database that serves as a portal for researchers to access information on samples and data
held, and to apply for access to both data and samples (Fig. 6.1).
One, centralized web-accessible database, held on secure servers at Imperial College
London holds anonymised information on donors to the CTB and the biological samples
donated by them. Regular, automated transfer of patient data back to secure servers in
Ukraine and Russia ensures that each center has a local mirror copy.
Detailed standard operating procedures for the collection and documentation of
specimens and blood samples have been agreed upon with professional staff involvedin the collection of material, and ethical standards agreed upon with the relevant
authorities, conforming to the requirements of each country involved and those of thefunding organisations. Each donor is identified by a unique alphanumeric code. Samples
from each donor are identified by suffixes to this code enabling the specimens and any
derivatives from them to be linked to the tissue block they were derived from and theindividual donor. Tissue and blood samples, and extracted materials are recorded withintables in the CTB database. The database schema allows easy transfer of data between
different database systems such as IBM DB2, Oracle, Microsoft SQL Server, MySQL, andPostgreSQL.
The samples database holds relevant information on the patient (date of birth, date ofoperation, sex, oblast of residence at the time of the accident and operation) together withpathological information and location coordinates for each sample of tissue, DNA or RNA
137

Chapter 6

Figure 6.1. The CTB data warehouse combines the Samples, Research and Integrative Databases,
Management and Search Modules with corresponding front-ends/interfaces. The system wasdeveloped with assistance from the Bioinformatics Support Services (BSS) at Imperial College, andcontinued close cooperation is essential for the smooth and secure integration of all the componentsof the overall system. Access to further samples and to information stored in the research databasefrom the use of previous samples in research from the same patient is provided by the CTB portal.

extracted from tissue, and blood, serum and DNA extracted from blood, and informationon the quality assurance of these derivatives is also recorded within the samples database.
Dosimetry information for each patient has been provided in collaboration with Professor
Ilya Likhtarov (see Chapter 2).
Security and integrity of the data in the CTB Data Warehouse is of paramount importance.
With regards to the Samples database and corresponding front-end, the access to data
sets is appropriately restricted according to a country (e.g. Ukraine, Russia) and a role (e.g.
pathologist, lab technician, administrator) to which a user belongs. Integration of the
Samples database with the rest of the system and transfer of data between different elementsof the overall CTB Warehouse are submitted to the same strict security requirements
and are designed to minimize the risks of data loss or theft. Regular, time and place
restricted updates of the Integrative database from the Samples and Research databases
provide the up-to-date link between the research data and the key clinical-data elements
required by a researcher.
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Ukrainian contribution to the international Chernobyl Tissue Bank (CTB)

Figure 6.2. Representative screenshots of the CTB portal. (2A) Login entry page. (2B) User
searches samples by selecting criteria of interest. As search filters are selected, numbers of samples
matching criteria are shown. (2C) Representative search results page showing available samples,
search criteria and additional data available for sharing.

The CTB Portal (https://cisbic.bioinformatics.ic.ac.uk/ctb/html_ctb_public/)
The CTB Portal provides on-line access to the resources of the CTB. Accessible either
directly or from the CTB web site, the Portal gives access to a simple, but powerful,search facility that allows a researcher to search the database and check if samples areavailable that match the requirements for their study. Biomaterials are defined by: thetype of thyroid tumor (from the consensus diagnosis of the Pathology Panel); the originof the sample – blood, tumor tissue or normal tissue; the type of sample – FFPE section;
extracted DNA or RNA; and key patient information such as age at exposure, residency,
etc. The results of the search show the number of cases that match the criteria and thenumber of samples that are available. The system went live on the 25th anniversary of theChernobyl accident. Representative screenshots of the Portal and the search filter are
shown in Figure 6.2.
The PI is guided through the on-line application process to request samples.
Management tools embedded within the Portal, and accessible only by the secretariat,
facilitate the processing of applications and tracking progress through the review andapprovals process. Once the applicant has submitted their application on-line, thesecretariat checks that the application is complete. The status of the application is altered as
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Chapter 6

it progresses through each stage of the process and an e-mail is automatically sent to the PI
acknowledging each change of status: (submitted for review, more information required,etc.). The software automatically compiles the various sections of the application into a
PDF. The secretariat then forwards this to the External Review Panel for assessment of thescientific quality of the project requesting access.
The integrative database produces a comprehensive list of all the cases identified thatmatch the search criteria entered by the applicant. This listing is available only to thesecretariat and is a significant step in the automation of the process of selecting appropriate
samples for a project. The process can never be totally automated and expert oversightof the pathological information will always be required. However, the initial screening
facilitates this procedure.
The CTB Portal also provides access to the Data Warehouse both for PIs to upload datafrom their approved CTB projects and for other researchers to be able to see if data isavailable linked to the cases they have selected.
Use of CTB samples in research
Biospecimens from the CTB have been provided to the major research groups involvedin the studies of the consequences of the Chernobyl accident. Information on the projects
receiving biosamples can be found at http://www.chernobyltissuebank.com/research.
html. Thirty projects have been approved for access to date; 11,901 samples have alreadybeen released to these projects. Of these, 11,498 were provided from the Ukrainian sectionof the CTB. Scientific evaluation of each project is provided by the CTB’s External Review
Panel (ERP) and the outcome of the review and, where appropriate, any feedback from the
ERP is provided to the applicant.
This approach provides a basis that fosters international collaboration and reduces the
chance of competition and even friction between groups in their requests for this material.
Researchers who obtain material from the resource agree to provide the results of theirinvestigation on a case-by-case basis to enable combined analysis to be carried out at alater date. The provision of extracted nucleic acid from thyroid tissue, rather than eachresearcher being provided with a small piece of tissue, maximises the amount of datathat can, potentially, be obtained from a single operative specimen and enables multiple
molecular biological studies to be carried out for each case. The median number of projects
supplied by material from a single case at present is 4 with some being used in more than
9 projects. Details of the publications resulting from material supplied by the project arelisted on the project website (www.chernobyltissuebank.com/papers.html). Data on Copy
Number Alteration, mRNA expression, SNP and mutation/translocation of thyroid cancer
key oncogenes RET and BRAF, is already available for over a quarter of the cases, with
miRNA array and methylation DNA array data being made available through the EU funded
EpiRadBio project. Similar data will also be available soon from patients enrolled in the
Ukrainian-American Cohort.

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Ukrainian contribution to the international Chernobyl Tissue Bank (CTB)

Results of Research studies
The pathology of all cases submitted to the CTB is reviewed by an International Pathology
Panel. Their review of the cases has suggested a new classification for thyroid cancer [5]and has shown that the latency affects the morphological subtype and aggressiveness ofpapillary cancers [6] with the frequency of the solid subtype falling from 24 to 6% over the
first two decades after the accident, and a similar decline in the frequency of extrathyroid
extension and lymph node metastases [7]. A more detailed explanation of the pathologicalfeatures can be found in Chapters 4 and 5 in this book.
The results of molecular biological studies that have used material from the Chernobyl
Tissue Bank are included in Chapter 7 in this book. An abstract of all projects authorized touse material from the CTB, and links to papers that have resulted from these projects, areavailable on the project website (www.chernobyltissuebank.com).
Thus, we can conclude that understanding the major drivers in tumour growth will
depend increasingly on being able to take a systems biology approach, rather than an
individual gene or analytical platform approach. It is already evident from the literaturethat a change in copy number at the DNA level does not always result in an increase in RNA
expression of all of the genes coded for by the amplified region, and that identifying criticalnodes within networks of converging signalling pathways will be necessary to understandthe functional biology of cancer [8]. Collating all of the research data generated from thesamples donated by those affected by the Chernobyl accident is a challenge. By collating
the data in a central resource, the CTB will facilitate not only projects that require access tosamples alone, but also projects that wish to link their results with data already available.
Tissue banks are likely to be key players in this type of cancer research in future and should
be designed from the outset to facilitate this aim.

References
1. Kazakov VS, Demidchik EP, Astakhova LN. Thyroid cancer after Chernobyl. Nature 1992;359:21.
2. Baverstock K, Egloff B, Pinchera A, Williams D. Thyroid cancer after Chernobyl. Nature 1992;
359:21-22.
3. Thomas GA, Pinchera A, Reiners C, Bauchinger M. Final report for EC contract FI4C CT98 0017; 2001.
4. Thomas GA, Bethel JA, Galpine A, et al. Integrating research on thyroid cancer after Chernobylthe Chernobyl Tissue Bank. Clin Oncol 2011;23:276-281.
5. Williams ED, Abrosimov A, Bogdanova T, et al. Two Proposals Regarding the Terminologyof Thyroid Tumors. Int J Surg Pathol 2000; 8:181-183.
6. Williams ED, Abrosimov A, Bogdanova T, et al. Thyroid carcinoma after Chernobyl latent period,
morphology and aggressiveness. Br J Cancer 2004;90:2219-2224.

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7. LiVolsi VA, Abrosimov A, Bogdanova T, et al. The Chernobyl thyroid cancer experience: pathology.
Clin Oncol 2011;23:261-267.
8. Faratian D, Clyde RG, Crawford JW, Harrison DJ. Systems pathology-taking molecular pathology
into a new dimension. Nat Rev Clin Oncol 2009;6:455-464.

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Molecular biology studies of Ukrainian thyroid cancer after Chernobyl

Chapter7

U Schoetz, V Saenko, S Yamashita,
GA Thomas

Molecular biology studies
of Ukrainian thyroid cancer after Chernobyl

Cancer is known to be an extremely complex disease that is caused by a variety of different
agents, including radiation. An understanding of the molecular mechanisms that generate
cancer, and the link between molecular features and aetiology, prognosis and responseto treatment is pivotal in the successful treatment of the patient. The unprecedented
increase in thyroid cancer following the accident at the Chernobyl power plant provided
the opportunity to understand the molecular biology of this type of malignancy, andto link molecular features with radiation aetiology. Thyroid cancer in young people is arare disease, with an incidence rate of around 0.5–1.5 cases per million per year [1]. Initialreports suggested that thyroid cancers that were observed in young people following theChernobyl accident were different from those from an unexposed population. However,more careful analysis showed that this rare variant, a solid type of papillary cancer thatshowed extensive invasion, was common in young patients, whether exposed to radiation
or not [2]. This contrasts with the classic and follicular variants of papillary carcinoma foundmore commonly in adults. Since the pathological appearance of a tumor is related to theintegration of the molecular events that are involved in its generation, a number of studies
have concentrated on defining the various genetic and epigenetic changes involved.
Cases from Ukraine, provided via the Chernobyl Tissue Bank (CTB) have been used
extensively in these analyses. The early studies concentrated on the frequency of activationof oncogenes already known to be pathogenic in papillary thyroid carcinoma (PTC).
However, more complex molecular techniques have developed in the last decade, andthe later studies concentrate on the identification of multiple molecular changes in thesetumors.
Changes in the Genome
Somatic DNA – single oncogene studies
Genetic alterations that induce the Mitogen activated protein kinase (MAPK) signalling
pathway are common in sporadic PTC. The MAPK pathway is involved in regulation ofdifferentiation, survival and cell growth, and its malfunction is well known to be tumor
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Chapter 7

promoting [3]. Common alterations include both gene rearrangements and point mutations.
Inversions and translocations of a given chromosomal region can lead to an activation of
an oncogene that is inactive in the normal thyroid cell. The commonest rearrangements in
PTC are those that involve paracentric inversion of part of chromosome 10, RET/PTC1 and
RET/PTC3, resulting in fusion with the H4 gene (CCDC6, D10S170) and NCOA4 gene (RFG,
ELE1), respectively. The BRAF oncogene which is frequently mutated (point mutation) in
adult PTC has also been found to be activated in a small number of radiation-induced PTC
following inversion on chromosome 7q [4]. Alterations in the BRAF and RET oncogenes areusually mutually exclusive [5,6].
Other studies have identified chromosomal breakpoints on 1p32-36, 1p11-13, 1q22,
3p25-26 and 7q32-36 [7-9] and a deletion on 11q [10], but their importance in radiationinduced childhood PTC remains unclear. One reason why some rearrangements occur more
frequently than others may be the close proximity of the two gene loci participating in therearrangement within the nucleus. This theory is supported in a study by Nikiforova et al.
on the PTC specific translocation of the RET and H4 genes thereby forming RET/PTC1 [11]. In
vitro irradiation studies show increased DNA end-joining enzymatic activity which argues infavour of a radiation-specific response related to gene rearrangement in thyroid cells [12].
RET/PTC gene rearrangement in Ukrainian cases
The RET gene is located on chromosome 10q11.2. Its breakpoints for rearrangement
are all located within intron 11. The encoded receptor tyrosine kinase has an extracellulardomain, a transmembrane domain and an intracellular domain [13]. Fusion of RET withother genes provides the tyrosine kinase domain with a new promoter and 5’ coding
region which leads to constitutive expression of the protein and transmembrane domain
is substituted by dimerization domains for ligand-independent activation [14]. There are
17 different RET/PTC rearrangements that have been identified in PTC, but inversionsof chromosome 10 resulting in RET/PTC1 and RET/PTC3 are the most frequent. The RET
proto-oncogene was already known to be involved in papillary thyroid carcinogenesis
in studies of sporadic cases where rearrangements have been found in up to 40% ofcases. Rearrangement has been shown to be restricted to the papillary type of thyroid
cancer [15,16] and occur frequently in small papillary carcinomas suggesting that it islikely to be a driving event in early tumorigenesis. The breakpoint in the DNA occurs
within an intron, which permits the use of reverse transcriptase PCR (RT-PCR) using
RNA extracted from the tumors as a useful tool for identifying PTCs that harbour RET/
PTC rearrangements. However, studies using this technique need to be interpreted withcaution, as it has been shown that the results are heavily influenced by the PCR protocol
used and tumor heterogeneity [17].
Initial studies post Chernobyl were carried out on Belarussian cohorts [18-20] andsuggested an increased frequency of RET/PTC rearrangement in radiation induced PTCs inchildren. In a study on Ukrainian cases, reported by Santoro et al. [21], of the 106 papillarycarcinomas which produced amplifiable RNA and were analysed for RET rearrangement using
rearrangement specific RT-PCR, 20 were identified as positive for RET/PTC1 and 15 for RET/
PTC3; one other tumor was positive for both RET/PTC1 and RET/PTC3. Analysis of the expression
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Molecular biology studies of Ukrainian thyroid cancer after Chernobylof the extracellular and tyrosine kinase domains was also performed independently in adifferent institute in 45 of the 106 cases. Twenty-two of these 45 tumors were positive forexpression of RET tyrosine kinase. No tumor sample showed positivity for the expression of
the RET extracellular domain only, suggesting that the RET tyrosine kinase expression was dueto the presence in these tumors of a RET rearrangement fusing the tyrosine kinase domainof the RET gene with an active promoter. Among these 45 cases investigated for RET tyrosine
kinase expression, there were 20 with an identified PTC1 or -3 rearrangement, including
one tumor which showed both PTC1 and -3; 18 showed RET tyrosine kinase expression. The
unexpected negative RET tyrosine kinase in two cases may have been the result of a lack ofsensitivity. Twenty-five cases lacked either a PTC1 or -3 rearrangement, 21 were negative for
RET tyrosine kinase expression, while four were positive. The positive RET tyrosine kinase inthese four cases could have resulted from the presence of a RET rearrangement other than
PTC1 or -3. Overall agreement between the two techniques was therefore present in 39 outof 45 cases (87%). The type of RET rearrangement correlated with tumor morphology; RET/
PTC3 dominated in the predominantly solid subtype and RET/PTC1 was more common in
the classical subtype of PTC. This is consistent with previous studies on other Chernobylrelated tumor cohorts [20,22,19] and with transgenic models of thyroid cancer in animals[23,24]. A cohort of 28 PTCs from Ukraine and 39 from Belarus was examined by Thomas etal. [25]. Patients received surgery 9-11 years after exposure to radiation and their age range at
operation was between 6-18 years. 60.7% of the Ukrainian and 51.3% of the Belarussian cohort
were RET/PTC positive. 23 PTCs harboured the RET/PTC3 rearrangement and 14 patients the
RET/PTC1. RET/PTC3 was found to be associated with the dominantly solid subtype of PTC,
whereas RET/PTC1 was associated with the classic subtype of PTC. Matched normal thyroid
tissue samples were negative for RET rearrangements. In addition, lymph node metastasesof 8 Ukrainian patients were examined. RET rearrangement was detected in all cases where
the rearrangement was already present in the primary tumor. One metastasis was found to
be RET/PTC positive although the primary tumor was negative. It had been shown that both
ionizing and external radiation [26] were able to induce RET rearrangements in vitro [27],suggesting that RET/PTC rearrangement in these tumors was a potential marker for radiation
exposure. RET/PTC3 rearrangement is more prevalent than RET/PTC1 and linked to the solid
subtype, which was, at the time believed to be more frequent in radiation induced tumors. In
the rare cases where it occurs in adult onset sporadic PTC, it was linked to a more aggressive,
invasive phenotype with a higher potential to metastasize [28]. Since the early pathologicalstudies suggested that the PTCs found in children post Chernobyl were more aggressive thantheir adult counterparts, it seemed logical to suggest that this rearrangement was importantin the solid subtype, aggressive PTCs, that were frequent in the short latency PTCs, whichwere being examined at that time.
However, in all the studies reported above there was an inherent problem. Frequenciesof RET rearrangement in young onset, post Chernobyl PTCs were compared with thefrequencies of this oncogene in adult PTCs. Later studies [29], some using age-matched
controls [30], have shown that the frequency of RET rearrangement in early onset PTC,
regardless of prior radiation exposure of the patient, is much higher than that found in
adult PTC, suggesting that the initial conclusions on RET rearrangement being a biomarker
for radiation exposure were incorrect.
145

Chapter 7

Tumor heterogeneity
RT-PCR is a useful tool, but does not allow identification of the proportion of cells thatcarry the RET/PTC rearrangement. It was noted that the strength of RT-PCR signal for RET/PTC varied considerably between cases, and that this might suggest that this may represent
intratumoral heterogeneity. Unger et al. [31] therefore examined 32 patients from the
Ukrainian cohort with a tumor latency of 9-12 years for the intratumoral distribution of
the RET/PTC rearrangement using FISH. FISH is a DNA hybridization method targeting
metaphase chromosomes or interphase nuclei on tissue sections. FISH is capable ofdetecting RET rearrangements without further knowledge of the fusion partners. It allows
for examination at the single cell level and can contribute to a better understanding of thetumor heterogeneity. Interphase FISH was chosen for the detection of the chromosomal
alterations involving the RET gene, [31,32]. Two YAC probes including regions within the
RET target locus and distal to the RET sequence were chosen and labelling was performed
using two different fluorescent dyes (Fig. 7.1). A confocal laser scanning microscope wasused for visualisation. Cell nuclei were scored for the presence of a separated red andgreen FISH signal in addition to an overlapping signal. This helps to avoid misclassification,
which is dependent on the location of the interphase chromosome 10 within the nucleus
and the spatial proximity of RET to putative rearrangement partners. Overlapping signals
occur only in normal nuclei, and split signals indicate an aberration of the RET gene. Thisapproach has been further validated by using careful selection of controls, including RET/
PTC positive and negative cell lines as well as wild type RET expressing controls (Fig. 7.2).

Figure 7.1. Mapping of YAC probes 313F4, 210H10 and 344H4 on chromosome 10q11.2. YAC
clones 313F4 and 214H10 (FITC-labelled, green) map proximal to and include the RET locus, 344H4(Cy3-labelled, red) maps distal to RET. Exons and different parts of the RET gene are indicated below(EC=extracellular domain, Cys=cystein-rich domain, TM=transmembrane domain, TK=tyrosine
kinase domain).

The study reported by Unger et al. [31], comprised 29 PTCs, two follicular adenomas,
and a follicular cancer. Detection of the RET rearrangement with conventional qRT-PCR
revealed that 13 (40.6%) of the patients expressed the TK domain of RET, and in only
146

Molecular biology studies of Ukrainian thyroid cancer after Chernobyl

two and three patients, respectively, was a clear RET/PTC1 and RET/PTC3 signal detected.
Investigation of the cases with FISH was more sensitive and 23 patients (72%) were positive
for the RET rearrangement. A threshold for positivity was set as evidence of rearrangement
in a minimum of 7% of cells within a tumor. The highest observed frequency of cells
bearing the RET rearrangement positive FISH signal was 46%. In none of the tumors wasa FISH positive signal observed in 100% of tumor cells. Further analysis showed that the
distribution of FISH positive cells was inhomogeneous.

Figure 7.2. Example of FISH analysis with RET-specific YAC probes using confocal laser scanningmicroscopy (CLSM). Three different areas were randomly selected from the tumor as indicated at the
40x magnification image (TOPRO image only, top center). One viewing area (left side) shows only
normal cells exhibiting overlapping FISH signals. Two other viewing areas (middle and right side)
show a cluster of aberrant cells identified by split FISH signals (arrows). All images are superimposedfrom approximately ten different slices throughout the thickness of the tissue section. For a more
precise evaluation a stepwise scoring every 0.5 µm is applied.

The same group repeated the RET rearrangement analysis on a Ukrainian cohortof 13 patients presenting with PTC after a shorter latency of 4-8 years post Chernobyl[32]. They compared this short latency group to the long latency group described
previously for the distribution of the RET rearrangement within a given tumor sample.
Examination with interphase FISH showed 10 of the patients (77%) were positive for a RET
rearrangement with a frequency of rearranged cells between 11-54%. In 9 cases, the RET
rearrangement was homogenously distributed all over the tumor tissue, whereas one caseshowed distinct clustering in certain areas of the tumor. Both studies identified a similarfrequency of intertumoral rearrangement of RET, but the intratumoral distribution of the147

Chapter 7

RET rearrangement between the groups differed significantly. The longer latency group
included a higher frequency of tumors with a heterogenous distribution and clusteringof the rearrangement. At the same time, others had noted that tumor morphology waschanging from a predominantly solid subtype in the shorter latency to a solid-follicularsubtype in the longer latency group [33]. The reason for this may be the outgrowth of
distinct subclones in longer latency tumors or the presentation of RET/PTC as a second
event in thyroid carcinogenesis.
In a later study, reported by Hieber et al. [34], interphase FISH analysis was used
to assess RET rearrangements of the cases. Aside from five other chromosomal
rearrangements, 16 of the cases (72%) were positive for RET rearrangements. This is a
rate similar to that observed in other studies [31,32]. With a threshold for RET positive of
7.1%, the number of rearranged cells per case varied from 10.6% to 41.5%. There was no
obvious correlation with age or gender of the patients, but the median age at operationof the patients carrying rearrangements was higher (22 years) compared to the groupwith no rearrangement (18 years). Within the group carrying rearrangements, older
patients showed greater tumor heterogeneity with respect to RET/PTC rearrangements,
consistent with the earlier study by Unger et al. [31].
The BRAF proto-oncogene
BRAF is a RAF kinase which plays an important role in the MAPK pathway. It ismember of the family of RAF proteins, and due to its serine/threonine kinase activity
it phosphorylates the MAPK/ERK kinase upon stimulation by RAS [35]. It is frequently
mutated in thyroid cancer, where the point mutation at nucleotide position 1799 is
the most prominent one. A transversion from thymine to adenine (T1799A) changes
the amino acid sequence in codon 600 from valine to glutamic acid (V600E); thus theabbreviations used to designate this mutation are BRAFT1799A or BRAFV600E. This results inconstituent activation of the gene, thus activating the MAPK pathway. The frequency ofmutation varies in a number of studies from 36-69% in adult papillary thyroid carcinoma[36,37], including one study on Ukrainian tumors [30]. In adult cases, BRAF mutation
significantly correlates with clinical parameters in PTC such as distant metastases,
advanced clinical stage and disease specific mortality [38]. In children, the involvementof BRAF has been found to be somewhat different. Kumagai et al. [39] performed a study
on childhood PTC from Japan and Ukrainian patients with PTC following the Chernobyl
accident, and compared the frequency of BRAF mutation with that found in adult PTCs.
Sequence analysis of the BRAFT1799A mutation in exon 15 found only one positive case in
the young Japanese cohort. No mutations in K-, H- or N-RAS were detected. The same
result was obtained for the childhood group (aged under 15 at diagnosis) within the
Ukrainian cohort. However, among the cases of young adults, 8 out of 33 carried the
BRAFT1799A mutation and two other cases carried RAS mutations, one in NRAS codon 61 andone in HRAS codon 61. The Ukrainian group was also examined for RET rearrangements.
5 out of 15 in the childhood group exhibited the rearrangement, and 12 out of 33 in thegroup of young adults. Mutation of BRAF and rearrangement of the RET oncogene were
mutually exclusive. Interestingly, in this study, the presence of the mutation was not148

Molecular biology studies of Ukrainian thyroid cancer after Chernobyl

associated with large tumor size, regional lymph node invasion, extrathyroidal invasion,or distant metastases.
Lima et al. [40] examined a cohort of 34 post-Chernobyl paediatric PTC from Ukraine
and found that four were positive for the BRAFV600E mutation. 14 of the patients had a RET/
PTC rearrangement, but BRAF mutation and RET rearrangement were, again, mutually
exclusive. The BRAF mutation occurs predominantly in the papillary and follicularvariants, whereas the RET rearrangements were more common in the solid subtype ofthe tumor. The control group of sporadic pediatric PTCs contained no solid variants, andthe frequency of RET rearrangement was not determined. Powell et al. [30] used 67 casesof post-Chernobyl PTC from Ukraine to examine whether the BRAF mutation was related
to the age of the patients or the radiation exposure. 32 patients were aged above 30 attime of clinical presentation, and 35 patients were under 16. All patients, exposed or
unexposed to radiation, were residents in the Ukraine and hence an ethnic difference asconfounder can be excluded. Paired tumor – normal samples were analysed and 18 outof the 32 adult cases were found to harbour the BRAFV600E mutation in the tumor but notin the normal tissue. The tumor morphology was of dominantly classic or dominantly
follicular subtype. Only one child in the group of 35 exposed cases was positive for the
mutation and none of the sporadic PTCs. Interestingly, the one case bearing the BRAF
mutation was of a dominant papillary subtype.
In summary, BRAF mutations are more commonly seen in PTCs with a dominantly
papillary morphology, and are more common in PTCs diagnosed in adulthood rather
than childhood. The low frequency of BRAF mutation in PTCs from children exposed or
not exposed to radiation suggests that, as with RET oncogene rearrangements, the ageof the patient at diagnosis is a significant factor. It is therefore important to ensure thatcases are appropriately age matched when seeking to identify radiation related changes
in molecular biology of tumors. One study has also shown that in post-Chernobyl PTCs
from Belarus, BRAF can be activated by gene rearrangement. In this case, the C-terminal
region of the BRAF gene is fused to the first eight exons of the AKAP9 gene building
the AKAP9/BRAF fusion gene [4]. However, as is the case with the early studies of RET
rearrangement in post Chernobyl PTCs, this study lacked age matched controls and it istherefore unclear whether this finding is related to radiation or to the age of the patient
at operation.
Other proto-oncogenes
Although RET/PTC and BRAF alterations are the commonest oncogene alterations
seen in PTC, rearrangements and mutations of other genes are also observed, but at
a much lower frequency. NTRK1 encodes the high affinity nerve growth factor (NGF)
receptor, and is occasionally rearranged in PTC. NTRK1 fusion partners are the genes
TMP3, TPR and TFG [41,42]. The NTRK1 rearrangement, is only present in about 11% ofsporadic PTCs [43], and is rare (3.3%) in post-Chernobyl thyroid tumors [44-46].
Other types of thyroid cancer are known to involve much different oncogenes, suchas the RAS oncogene [47] in follicular carcinoma or TP53 in anaplastic carcinoma [48].
Mutations of the thyroid stimulating hormone receptor (TSHR) gene occur in follicular
carcinoma and benign thyroid tumors [49,50]. Santoro et al. [21] examined whether one
149Chapter 7of these molecular changes had an influence on the development of PTC after exposure
to radiation. The group studied 128 PTC of post-Chernobyl patients who received
surgery before the age of 15, all of whom were from Ukraine. In addition to RET
rearrangement, reviewed in the section above, mutations in the RAS, TP53 genes, andexon 10 of the TSHR were also analysed and correlated with the morphological status of
the tumor samples.
Alterations in the other genes of interest were not found to be present in the postChernobyl PTC cohort. Other studies could also not demonstrate correlation of TSHR
or TP53 mutations in thyroid carcinogenesis after radiation exposure [51-54]. RAS
mutations are not commonly found in sporadic PTCs, although they are identified infollicular thyroid tumors, and detection in radiation-induced childhood PTC is similarlyrare [39,53,55].
These results show that mutations in the TP53 and H-, N-, and K-RAS genes play noimportant role in the carcinogenesis of radiation-induced PTC.
Studies on genomic profiling
Array-based comparative genomic hybridisation (aCGH) is a technique that allows an
objective and quantitative examination of copy number changes of the entire genome ata high resolution. BAC clones covering the whole genome in 1MB distances are spotted on
glass slides and used for hybridisation with probe sequences of a tumor sample. Genomic
alterations such as deletions or amplifications are detected with a greater sensitivity andimproved resolution (1MB) than by karyotyping, but chromosomal rearrangements such astranslocations and inversions cannot be identified using this technique. aCGH is also capableof detecting copy number variations which occur regularly in normal tissue and need to be
distinguished from their pathogenic counterparts.
Unger et al. [56] analysed 33 patients who developed PTC following the Chernobyl
accident for chromosomal aberrations using aCGH and validated the results by FISH. The
cohort was a mix of 13 children and 20 adults with known RET/PTC rearrangement status.
RET/PTC positive cases and RET/PTC negative cases were compared, as well as children
versus adults. In all cases, deletions occurred with a higher frequency than amplifications.
This might have been predicted, as radiation is thought to introduce chromosomal breaks
which may lead to deletions, translocations or inversions rather than a chromosomal gain.
Losses were predominantly on chromosomes 1, 6, 7, 9, 10, 11, 12, 13, 16, 19, 20, 22 and gains
on chromosomes 10, 12, 19, 20, 21. Hierarchical clustering distinguished the three groups;
childhood RET/PTC positive, adult RET/PTC positive and adult RET/PTC negative. RET/PTC
positive cases differed significantly for a region on chromosome 1p which was deleted in
adults, but not in children. All RET/PTC positive cases differed significantly from the negative
cases in losses on 1p, 7p, 9, 13q and gains on 3q, 4p, 12q, 21q. Deletions of regions on
9q, 10p, 10q and 22q had also been observed in other studies on thyroid tumors [57-61].
Hence, these aberrations seem to be more specific for carcinogenesis in thyroid than for the
exposure to radiation and hence cannot be considered as radiation specific biomarkers. Gene
detection in the altered regions revealed 31 candidate genes which are known to be involvedin tumor progression and 21 tumor suppressor genes which specifically map to deleted
chromosomal regions. It is of note that the majority of these genes is known to be involved
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Molecular biology studies of Ukrainian thyroid cancer after Chernobyl

in thyroid carcinogenesis, and a further study giving a comparison with sporadic PTCs would
be necessary to define a specific role in radiation induced tumor development. The genes
identified are involved in the molecular pathways of apoptosis, interleukin-27, angiopoietin
receptor and the PI3K/MAP kinase. The data reflects a large heterogeneity in post-Chernobyl
PTC which suggests the existence of various routes of tumor development. In terms ofbiomarker screening this may imply that a whole panel of markers will be necessary for an
exact detection of a radiation signature.
Stein et al. [62] used tumor and matching normal tissue of 10 Ukrainian patients withpost Chernobyl PTC to examine copy number changes and gene expression. The latency forthese tumor patients was 13-14 years, and age at exposure varied from 3 months to 18 years
whereas age at operation was from 14-31 years.
In studies on sporadic PTCs, copy number alterations (CNAs) are detected with a low
frequency. Depending on the study, the occurrence of gains and losses ranges between
2-50% [7,59,63]. Detection is strongly dependent on the method used and the conventional
CGH and cytogenetic approaches used in these studies have not the same high resolution as
the currently used array-based CGH (aCGH). Stein et al. used high resolution SNP array CGH
technology for CNA examination. Several amplifications on chromosome 22 were detected
in all 10 samples. Also, chromosomes 1 and 12q show amplifications with high frequency.
Further, less frequent amplifications on 5p, 9q, 16p, and 21q were also detected. Deletions
were identified in chromosomes 21q and 14q, and several deletions on 1q, 6p, 9p, 10p, 13q,
and 22 were restricted to 2 tumors specifically. In general, deletions were less common in
PTC than amplifications independently from radiation exposure or sporadic occurrence.
Although radiation is thought to generate an increased amount of deletions, translocations
and inversions due to chromosomal damage, there is no direct evidence that the number ofchromosomal aberrations in radiation-induced PTC is higher than in sporadic PTC. However,some aberrations seem to occur preferably after radiation exposure. Chromosome 22 wasreported in several studies to be affected in post Chernobyl patients [59,64,65] and was
associated with tumor aggressiveness in younger patients. Gene expression of genes in theseregions was determined and compared with gene expression in sporadic tumors. 41 genes
were specifically upregulated in post Chernobyl pediatric PTC but not in sporadic PTC, andthe ones with the strongest overexpression were TESC, PDZRN4, TRAA/TRDA, GABBR2, CA12,MPZL2, SCG5, PDZK1IPI, AMIG02, NOVA2, and TNIK. The genes with the largest downregulationof expression from a total of 24 genes were PAPSS2, PDLIM3, BEXI, ANK2, SORBS2, PPARGCIA,
MT1M, CTGRF, LYVE1, and OGDHL. Only one gene on chromosome 22, FBLN1, was reported to
be specifically downregulated. It would be of interest to examine these genes further for theirpotential usefulness as biomarkers of radiation exposure.
Another study on chromosomal aberrations was carried out by Hieber et al. [34]. A cohortof 23 patients from the Ukraine who developed PTC after the Chernobyl accident were
examined for chromosomal aberrations and RET/PTC rearrangements. The median age ofthe patients at operation was 21 years old. SKY (spectral karyotyping) was performed andrevealed chromosomal aberrations in 14 of the cases, most frequent on chromosomes 7, 10,
11, 21, and 22. It is unknown whether these aberrations are related to radiation exposure as
no group of sporadic PTC was included in this study [6,13,14]. As discussed earlier, studies
on sporadic thyroid cancer had already described aberrations of chromosome 22 as acytogenetic event in subtypes of PTC.
151

Chapter 7

None of the above mentioned studies was able to define a biomarker specificallytargeted to radiation exposure. This may be partially due to the design of the studies asconfounders such as age at operation, ethnic origin and histology of the tumor play a role inthe molecular phenotype of tumors, and the cohorts studied often lack matched controls.
Hess et al. [66] designed a study to specifically address the question whether there
are genomic alterations that correlate with exposure to radiation. A cohort of 56 patientswith PTC was matched by age at operation and residency. The patients were known to
be exposed to radiation (33 patients born before April 1986) or not exposed to radiation(19 patients born after January 1987). A second cohort of 28 PTCs (16 exposed and 12
unexposed) matched on the same criteria was selected to validate the results. aCGH
and FISH were performed as reported in a previous study [56] to evaluate chromosomal
aberrations that differed between exposed and unexposed cases. Amplifications were
found to be more frequent than deletions which are in agreement with the findings of Steinet al. [62]. In general, DNA gains (n=81) were more frequent than DNA losses (n=63). Five
regions on chromosomes 1, 3, 4, and 12 were lost, and six regions on chromosomes 12, 19,
20, and 22 were gained in all cases investigated. Hierarchical cluster analysis separated thearray CGH proﬁles into two main clusters, 1(n=23) and 2 (n=29). Cluster 2 was subdivided
into two subclusters, 2-1 (n=14) and 2-2 (n=15). Cluster 1 contained signiﬁcantly more RET/
PTC positive cases compared with cluster 2 (p=0.0096). Large tumors (pT2 and pT3) wereassociated with cluster 1 (p=0.00087). Tumors that had metastases to regional lymph nodes(N1) were predominant in cluster 1 and cluster 2-2 (p=0.04). Univariate supervised analysis
showed associations [false discovery rate (FDR) <0.05] of CNAs with tumor size (gain of
1q21.1–23.3, 7q22.1, 9p24.3, 10p15.3–15.1, 10q26.13–26.3, 11p11.12-cen, 12q24.11–24.23,
and 16q22.1–23.3) and sex of patients (loss of 5q23.3–31.3). A DNA gain on chromosome
7 (7p14.1-q11.23, 32.1Mb in size) was exclusively associated with a subgroup of patients
exposed to radiation after Chernobyl (univariate supervised analysis; FDR<0.05). The
alteration was present in 13 out of 33 cases from the exposed group and in none of the cases
from the unexposed group (p=0.0015, FDR=0.035). This ﬁnding was veriﬁed by array CGH
analysis of an independent validation set consisting of 28 PTC cases (16 exposed and 12
unexposed). FISH analysis of individual cases revealed that up to 24% of tumor cells exhibit
the amplification of 7q11. As the cohort was matched on the confounding parameters age,residency and RET/PTC status, the gain of 7q11 could be described as the first potential
marker identified for exposure to radiation. Nine genes identified within this region wereassociated with tumor development according to gene ontology analysis. The five genes
CLDN3, CLDN4, LIMK1, PMS2L2, and RFC2 showed no significant change in expression,
whereas the three genes PMS2L3, PMS2L11, and STAG3L3 were significantly overexpressedin tumors with gain compared to those with normal copy number. CLIP2 was found to beoverexpressed in exposed tumors in general, independently from the presence of the gainof 7q11. CLIP2 (Cap-Gly domain main containing linker protein 2) is a relatively unknown
gene with putative functions in microtubule formation, chromosome segregation and cell
division. As these are mechanisms which become perturbed in cancer development, there
might be a cancer-related function of CLIP2, but its involvement in tumorigenesis, andespecially radiation-induced tumor development, is currently unknown.
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Molecular biology studies of Ukrainian thyroid cancer after Chernobyl

Interestingly, the gain on chromosome 7q11 was already reported in a previous studyof Richter et al. [61], who used conventional CGH to analyse chromosomal aberrationsin post-Chernobyl PTC. A cohort of 60 children presenting with PTC after the Chernobyl
accident was used for the study. The 48 female and 12 male patients were matched on age
at exposure, age at operation and residency. 30% (18 cases) had an altered chromosomal
profile. The most frequent deletions were observed on chromosomes 16p, 16q, 20q and
22q, and amplifications of chromosomal regions on chromosomes 4, 7q11.2-21, 13q21-22,
and 21. The region 7q11.2-21 overlaps with the region described in Hess et al., but noneof the other CNAs identified in this study correspond with those found by Hess et al. The
other CNAs idenified may be more related to the age of the patients at operation or the
behavioural characteristics of the tumor. Deletions on chromosome 22 occur in PTC ofpatients of younger age and thyroid carcinoma with an increased invasive and metastatic
potential [67,68,59]. Imbalances on chromosome 16 were reported earlier to be involved invarious forms of thyroid cancer [69,57].
The results of these studies are summarised in Table 7.1.
Table 7.1
Overview of genomic abberrations found in the Ukrainian cohort
Author[ref.]

chromosomal
chromosomal
alterations gains alterations
lossesObservedin sporadic
cases

Unger etal., 2008[56]

chromosomes 10, chromosomes
12, 19, 20, 21
1, 6, 7, 9, 10,
11, 12, 13, 16,
19, 20, 22

chromosomes
9q, 10p, 10q
and 22q

Stein et al.,2011 [62]chromosomes
22, 1, 12q, 5p, 9q,
16p, 21q

Hieber etal., 2011[34]

chromosome 7, 10, 11, 21 and 22

Hess et al.,2011 [66]chromosomes 12, chromosomes
19, 20, 22, 7q11
1, 3, 4, and 12

chromosomes
1, 3, 4, 12, 19,
20, 22Richter etal., 2004[61]

chromosomes
4, 7q11.2-21,
13q21-22, 21

chromosomes
16, 22

apoptosis, interleukin-27,
angiopoietin receptor
and the PI3K/MAP kinase
pathways
Upregulated: TESC, PDZRN4,
TRAA/TRDA, GABBR2, CA12,MPZL2, SCG5, PDZK1IPI,
AMIG02, NOVA2, TNIK.
Downregulated: PAPSS2,PDLIM3, BEXI, ANK2, SORBS2,
PPARGCIA, MT1M, CTGRF,LYVE1, OGDHL, FBLN1

chromosomes
21q, 14q, 1q,
6p, 9p, 10p,
13q, 22chromosomes
16p, 16q, 20q,
22q

genes/pathways

Upregulated: PMS2L3,PMS2L11, STAG3L3, CLIP2

153

Chapter 7

Germline Genome
Genetic association studies using germline DNA variants
Genetic association studies are aimed at the exploration of the link between genotype
and phenotype to facilitate the determination of genetic risk factors for the potential
development of disease. These studies evaluate gene polymorphism, usually the single
nucleotide polymorphism (SNP) in retrospective or prospective case-control studies.
In general, there are two methodological approaches to selecting which and/or how
many SNPs need to be analyzed. The first one, the so-called candidate gene approach,hypothesizes that genetic variations in one or in a limited number of genes may influence
the risk for or the phenotype of a given disease. A more comprehensive way is hypothesisfree; it employs analysis of the whole genome, hence the genome-wide association study(GWAS). To date, a number of investigations have been done in the area of thyroid cancer,
mostly in sporadic cases, with a few of those exploring the radiation-induced thyroid cases.
Candidate gene approach
In a study investigating loss of heterozygosity (LOH) for three different SNPs of the RET
gene (G691S, L769L, and S904S), no evidence of such was observed in 28 of 46 radiationrelated papillary thyroid carcinomas (PTC) from Ukraine and Belarus that were heterozygous
for at least one of the three SNPs under analysis [70]. A microarray investigation performed
later and independently was consistent with these findings [71]. In the additional 68 cases,
the rare S allele of G691S was significantly more frequent in patients older than 30 years old
as compared to the younger subjects. Since excess radiation risk for PTC in the individuals
exposed after they are 20 years old is low and it further declines with age at exposure, thestudy concluded that RET polymorphisms may rather influence sporadic but not radiationinduced thyroid carcinogenesis.
A study of the Arg72Pro polymorphism of the TP53 gene (which encodes a tumor
suppressor protein TP53 commonly reffered to as p53) in 48 pediatric/adolescent and 68
adult patients with PTC exposed to Chernobyl radiation from Ukraine and Russia, and 53
adult patients with sporadic PTC and 313 healthy controls from Russia found that the Arg/
Arg homozygotes were significantly less frequent in adult patients than in children andadolescents [72]. No LOH or imbalanced TP53 allele expression was observed in tumor
tissues of heterozygous individuals. It was proposed that TP53 genotype other than Arg/
Arg may contribute to the risk of development of PTC in individuals exposed to radiation
during their late childhood, adolescence or in young adulthood, particularly in females
aged between 18 and 30. Interestingly enough, an elevated risk for thyroid cancer was
reported in females exposed to Chernobyl fallout at the age below 30 years in a radiation
epidemiological investigation [73].
A subsequent study extended to the analysis of 9 SNPs in 5 genes involved in DNA
damage response (ATM, XRCC1, TP53, XRCC3 and MTF1) performed in 255 PTC patients(123 from Chernobyl areas and 132 sporadic) and 596 healthy controls (198 residents ofChernobyl areas and 398 subjects without history of radiation exposure) demonstrated that154

Molecular biology studies of Ukrainian thyroid cancer after Chernobyl

the ATM G5557A and XRCC1 Arg399Gln polymorphisms, regardless of radiation exposure,
were associated with a decreased risk of thyroid cancer [74]. Of note, the ATM IVS22-77 T>C
and TP53 Arg72Pro SNPs interacted with radiation exposure: the ATM IVS22-77 associatedwith the increased risk of sporadic PTC whereas TP53 Arg72Pro correlated with the higher
risk of radiation-induced PTC in adult patients, in support to the study which involved the
Ukrainian patients described above [72]. An issue of gene-gene and gene-environment
interactions was addressed in the analysis of ATM/TP53 genotypes. Some of those strongly
associated with either sporadic or radiation-induced cancer suggesting that polymorphismof these genes may modify the risk for PTC of different etiology.
Genome-wide association studies
The genome-wide association studies (GWAS), sometimes also referred to as molecularepidemiology investigations, are conducted using advanced technologies to rapidly andcost-effectively analyze genetic differences between individuals with specific diseases
compared to healthy individuals. Usually, the studies are performed in two or morestages. First, genotyping of a large number of SNPs in a relatively limited sample set,
which is called the training set, is performed on microarrays. The purpose of this stepis to tentatively determine the potential candidate polymorphisms at liberal p value.
Subsequently, genotyping of full or narrower set of SNPs in, again, a relatively small sample
set is undertaken to achieve more stringent p value. Further on, a validation study is
performed by genotyping a narrow set of pre-determined SNPs in an extended sample
set to increase p value stringency or to disprove the association. This last step is commonly
performed in the single-track assays such as e.g. TaqMan. Finally, a strict statistical metaanalysis is done, which combines the results obtained at different stages, with correction
for multiple testing. Eventually, one or several SNPs might be determined as conferring theassociation with the risk for disease. A functional study might be further undertaken toclarify the mechanism by which this SNP or a gene with which this SNP is in strong linkage
disequilibrium (LD) might be involved in the pathogenesis of a given disorder.
Before discussing the results obtained in Chernobyl PTCs, it is necessary to mention
several appropriately powered studies of genetic predisposition to sporadic thyroid cancer
published recently. The first one, employing a sample set of 962 cases of differentiatedthyroid cancer (i.e., mostly PTC and limited number of FTC combined) and 38,923
controls, reported rs965513, a SNP located at chromosome 9q22.33, 59 Kb upstream(centromeric) to the FOXE1 gene encoding a thyroid-specific transcription factor TTF2, as
the strongest genetic marker (OR=1.75; 95% CI 1.59-1.94; p=1.7x10-27) associating withthyroid malignancy in individuals of Iceland, Spain and the USA of European descent [75].
This study also claimed another SNP, rs944289, on chromosome 14q13.3 in the area of
the NKX2-1 gene that encodes the TTF1 transcription factor, to be a marker for thyroid
cancer (OR=1.37; 95% CI 1.24-1.52; p=2.0x10-9). A consequent study of the same group,
based on a sample set of up to 1,150 cases and 41,448 controls, found 3 additional SNP
associating with low TSH levels in population also to be the markers of risk for thyroid
cancer. These are rs966423 on 2q35 (OR=1.34; 95% CI 1.22-1.47; p=1.3x10-9), rs2439302
on 8p12 (OR=1.36; 95% CI 1.23-1.50; p=2.0x10-9) and rs116909374 on 14q13.3 (OR=2.09;
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95% CI 1.68-2.60; p=4.6x10-11) [76]. With regard to genetic markers in the FOXE1 proximity,
it is important to take into account the results of an independent study of 768 tag-SNPs
in 97 genes which were initially genotyped in 615 PTC cases and 525 controls from Spainand then in 482 patients with PTC and 532 controls from Italy for validation [77]. The target
genes were selected based on their differential expression in primary thyroid tumors or
the involvement in thyrocyte biology, metabolism and/or carcinogenesis such as the MAP
kinase, JAK/STAT and TGF-beta pathways. An SNP, rs1867277, within the LD block spanning
FOXE1 and located at the 5’UTR of the gene was identified to associate with PTC (OR=1.49;
95% CI 1.30–1.70; p=5.9x10-9). Functional study demonstrated that this SNP affects FOXE1
expression by differentially recruiting the USF1/USF2 transcription factors.
At present, the results of only one investigation of Chernobyl PTCs from Belarus
employing GWAS have been reported [78]. The developments of this project, however,required the involvement of additional PTC cases and controls from Ukraine. Therefore, it
seems pertinent to describe this study here.
During the first phase of the molecular epidemiology study undertaken in the frameof Nagasaki University’s Global COE Program supported by the Ministry of Education,
Culture, Sports, Science and Technology (MEXT) of Japan for 2007-12, a total of 667
patients from Belarus diagnosed for PTC in 1989–2009 and 1,275 controls from Belarus
and Russia were studied, of which 408 cases and 627 controls were genotyped using
the Illumina microarrays accommodating over 500,000 human SNPs; the rest of samples
were subjected to the validation study. Statistical meta-analysis has discovered 3 SNPs atchromosome 9q22.33 significantly associating with Chernobyl PTC with a p-value orderof 10-9 (Fig. 7.3). This value indicated a very significant association which surmounted the
genome-wide threshold of 2x10-7. For one of the detected SNPs, rs965513, which wasused for validation, a p-value of 4.8x10-12 and an odds ratio of 1.65 (95% CI 1.43–1.91) was
obtained after meta-analysis.

Figure 7.3. Manhattan plot of the GWAS results of the first stage of Chernobyl PTC study. The pvalues calculated by the Trend chi-square test for 506,840 autosomal SNPs are plotted in -log10 scalewith respect to their chromosomal positions. The horizontal line indicates the Bonferroni adjusted pvalue for genome-wide significance.

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In the second phase of the study, the sample set was expanded to include additionally
286 PTC cases from Belarus and 145 from Ukraine, and 257 controls from Belarus, 157 from
Ukraine and 620 from Poland. Thus, a total of 1,098 PTCs from Belarus and Ukraine, and2,309 controls (both cases and controls that passed the quality control) from the three
countries were included. The number of samples genotyped using Illumina microarrays
was 847 PTC cases and 1,240 controls; validation study using single-track TaqMan assays
included 274 cases and 1,023 controls.
Among all the targets tested, only 3 SNPs displayed significance in the training andvalidation sets while all other did not pass validation. Two SNPs were around or in the FOXE1
gene locus on chromosome 9q22.33: rs965513 (OR=1.69; 95% CI 1.51–1.90; p=5.8x10-19),
and rs1867277 (OR=1.52; 95% CI 1.26–1.83; p=1.4x10-5). The third SNP that displayed
significant association was in the NRG1 locus on chromosome 8p12, rs2439302 (OR=1.35;
95% CI 1.16–1.57; p=9.1x10-5). Notably, all three SNPs detected in our Chernobyl series had
effect size, in terms of OR, very similar to those reported in sporadic thyroid cancer studies.
Based on these observations it was concluded that these SNPs are the markers of PTC ofeither radiation or sporadic etiology.
It is worth mentioning that besides the 3 SNPs that displayed significant association
signals, the study also identified 11 potential candidate SNPs in or around 10 genes whichwere significant on microarray analysis with p values ranging 4.7x10-7 – 1.6x10-4. However,none of them, when subjected to validation study, passed it displaying the p-values from0.07 – 0.944. Therefore, all of them were conservatively judged as having no association
with Chernobyl PTC even though their significance (a p-value) for association ranged
6.0x10-6–5.0x10-3 on final meta-analysis. The SNPs in vicinity of NKX2-1, MBIP and DIRC3
previously reported to be associating with sporadic thyroid cancer were insignificant in the
study thus pointing on the specific association of these genes with sporadic thyroid cancer.

Figure 7.4. Risk factors for development of papillary thyroid carcinoma after internal exposure
to radioiodine. Genetic predisposition is added to those previously established to affect the risk:
exposure dose, younger age at exposure, iodine deficiency, male sex. Note that genetic markers
associating with risk for Chernobyl PTC are the same found for sporadic PTC, around or in the FOXE1(the strongest) and NRG1 gene loci. Several markers appear to be associating with the risk forsporadic thyroid cancer only: in or around the DIRC3, NKX2-1 or MBIP genes.

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As a whole, molecular epidemiology study of Belarussian and Ukrainian PTCs leads toan important corollary that among the genetic factors affecting risk for radiation-induced
thyroid cancer, the strongest markers are the same that confer predisposition to the sporadic
form of this type of malignancy. Genetic markers of radiation-related and sporadic partly
overlap yet the absence PTC-associating markers on 14q13.3 (i.e., NKX2-1 or MBIP), and 2q35
(DIRC3) from the Chernobyl series suggests they are specific to PTC developing without
radiation history. As shown in Figure 7.4, the results obtained in the study of Chernobyl
PTC permit the inclusion of genetic predisposition to the list of risk factors for radiationinduced thyroid carcinogenesis known from the earlier experience. The fact that GWAS
has not revealed genetic markers specifically associating with radiation-related but not
sporadic thyroid cancer does not rule out the possibility of their existence. Further studies
with higher resolution, such as e.g. next-generation sequencing, may shed light on thisproblem and will probably refine our understanding of radiation-induced carcinogenesisby addressing issues of gene-gene and gene-environment interactions.
Possible implication of FOXE1 in pathogenesis of PTC
The three genetic studies, two of sporadic thyroid cancers and one of radiation-induced
Belarussian and Ukrainian PTC, have concordantly identified the FOXE1 (TTF2) locus as amarker of inherited susceptibility for PTC of different etiology [75,77,78]. The intronless
FOXE1 is a member of the forkhead/winged helix family of evolutionarily conserved
transcription factors [79]. In humans, FOXE1 is a key player in thyroid organogenesis,
thyrocyte precursors migration and differentiation with onset of expression in the
thyroid primordium at Carnegie stage 15 [80,81]. FOXE1 is a transcription activator of
thyroperoxidase (TPO) and thyroglobulin (TG) genes [82,83].
FOXE1 involvement in thyroid diseases remains scarcely addressed. Using RT-PCR or insitu hybridization, Sequeira et al. found FOXE1 (TTF-2) expression in about 60% of human
thyroids [84]. In benign thyroid lesions FOXE1 expression was observed in 43–100% cases.
In thyroid malignancies, FOXE1 was expressed in 44% follicular carcinomas, 65% PTC and 0(of 2) anaplastic carcinomas. Nonaka et al. reported strong diffuse immunohistochemical
TTF-2 staining in 50 – 100% tumor cells in PTC, follicular adenoma, follicular carcinoma andpoorly differentiated thyroid carcinoma [85]. Medullary thyroid carcinomas were weakly
positive in 75% cases and anaplastic thyroid carcinomas were virtually all negative. In a
study by Zhang et al., nuclear expression of TTF-2 was found to be gradually decreasing fromfollicular adenoma to anaplastic carcinoma in accordance with tumor dedifferentiation[86]. Abnormal TTF-2 expression in the cytoplasm displayed the opposite trend except foranaplastic carcinoma in which TTF-2 expression was generally low. Despite genetic studies
strongly suggest FOXE1 implication in PTC, and there is an alteration of FOXE1 expression
and localization in cancer cells, its role in tumor development remains unknown.
To clarify the role of FOXE1 in PTC, the patterns of FOXE1 immunohistochemical expressionin 42 tumors and adjacent normal thyroid were analyzed, and then their relationship withmorphological characteristics of the tumor and patients’ genotypes was investigated [87].
FOXE1 exhibited nuclear and cytoplasmic staining in normal thyroid follicular cells.
Nuclear immunoreactivity was strong or moderate, while cytoplasm showed weak-intensity
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staining. Approximately one-third of all nuclei were not stained, whereas no cytoplasmic
expression was noticed in about 25% of cells. More uniform pattern of FOXE1 expression
was observed in thyroid cells at the vicinity of PTC border within 100-300 μm tissue layer
in which most cells showed strong nuclear and moderate cytoplasmic immunoreactivity.
FOXE1 expression in cancer tissue displayed approximately the same extent as in thenormal counterpart. Cells at the tumor border and those in close proximity to the border
showed the highest intensity of cytoplasmic and nuclear expression. Neoplastic cells in thetumor center exhibited substantially lower intensity scores and an obvious loss of nuclear
expression.
A significant increase of total FOXE1 score in cancer tissue compared to normal thyroid(p<0.001) which was contributed mainly by the cytoplasmic expression was found while thenuclear expression remained higher in non-neoplastic thyroid cells (p<0.001 and p<0.05,
respectively). Thus, cytoplasmic FOXE1 expression was an essential feature of cancer cells
whereas prominent nuclear expression was characteristic for normal cells.
Statistical analysis confirmed preliminary observations of the gradient FOXE1 expression
from central to peripheral areas of tumor and normal counterparts. Both cancer andsurrounding normal thyroid tissue demonstrated the strongest FOXE1 expression in theareas immediately adjacent to the tumor border comparing with the staining scores of
distant regions (p<0.001). Of note, the highest nuclear scores were on the normal tissue
side and the highest cytoplasmic scores on the cancer side. There were notable changes in
FOXE1 immunoreactivity with distance from the tumor border, such as increasing numberof negative nuclei in normal thyroid tissue and increasing number of negative nuclei alongwith decreasing cytoplasmic intensity in cancer tissue (Fig. 7.5).

Figure 7.5. Four distinct patterns of immunohistochemical FOXE1 expression in different zones
of normal thyroid (A and B) and tumor tissue (C and D), original magnification ×200. (A) In the normal
thyroid tissue at the distance >300 μm from the tumor border there is a considerable variation of
nuclear and cytoplasmic FOXE1 expression with 25 – 35% FOXE1 negative cells. (B) In the normal
thyroid tissue immediately (≤300 μm) adjacent to invasive or encapsulated tumor border) mostcells are FOXE1 positive with the highest nuclear and moderate cytoplasmic intensity. (C) In thetumor tissue at the invasive front or subcapsular region (<300 μm) regardless tumor border contacts
adjacent thyroid parenchyma or extrathyroid tissues, virtually all cells demonstrate the strongest
cytoplasmic and moderate nuclear FOXE1 expression. (D) Tumor tissue at the distance >300 μm
from the tumor border shows mainly monomorphic low to moderate cytoplasmic expression withnegative or weak nuclear staining.

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On multivariate logistic regression analysis it was demonstrated that among all
demographic and pathological variables entered in the model, only two, namely tumor
multifocality (p=0.032) and rs1867277 polymorphism in the FOXE1 5’ UTR (p=0.037),
significantly associated with nuclear FOXE1 expression in the zone of tumor cells confinedwithin the 300 μm to the tumor border; capsular invasion displayed marginal significance(p=0.051). Both multifocality and variant genotype other than homozygous for the major
allele (the dominant model of inheritance) associated with the higher FOXE1 expression.
Thus, FOXE1 displays an aberrant cytoplasmic expression in PTC suggestive of a possibilityof a role other than transcription factor or of the existence of other factors causing translocation;
perhaps such translocation may contribute to cancer cell biology. FOXE1 overexpression in
the cytoplasm in tumor cells may also reflect activation of FOXE1 regulating pathways (Shh/Gli and Wnt) which are switched on during thyroid carcinogenesis [88]. The precise role ofcytoplasmic FOXE1 requires functional studies to determine whether it is an active process
involved in carcinogenesis or it is a consequence of malignant transformation.
The interface between normal and cancer tissues is a battlefield of invading cancer cells
and the host. Many biological processes in cancer show highest intensity at the border, e.g.
cell metabolism changes, proliferation, neovascularization, and invasion. The significant
difference of FOXE1 expression between the periphery and the center of PTC is in line withthese notions of particular processes at the tumor border. The gradient in non-neoplastic
thyroid tissue adjacent to PTC was also found. Such kind of distribution is not described
well for normal counterpart. Observations of the sharp reduction of FOXE1-positive cellswith the distance from the tumor border imply FOXE1 involvement in communication at
the host/tumor interface.
Transcriptomic studies
Gene expression analysis
The previous sections have concentrated on the molecular aberrations identified in the
genome. Although many of these will result in changes at the RNA level, other factors canaffect RNA expression. The next section therefore summarises data from transcriptomic
studies using RNA expression techniques.
The power of the microarray technology in contrast to conventional analysis is in enabling
an observation of the genome-wide gene expression profile for a given population within asingle experiment. Gene-specific oligonucleotide sequences are spotted on glass slides andused for hybridisation of a preprocessed RNA sample. Technical issues such as non-specificbinding of the fluorophore or hybridisation artefacts can influence the evaluation and need
to be controlled for. The large amount of data created may be difficult to analyse and needs
implementation of explorative statistical tools for normalisation and correction, as well as
for detection of significant hits. Gene expression microarray studies are carried out to definediagnostic and prognostic markers and signatures. In Ukrainian post-Chernobyl PTCs, several
studies were specifically designed to address the question whether there is a molecularsignature for radiation-induced thyroid cancer. Table 7.2 gives an overview of the outcome.
No significant findings were reported concerning the transcriptome of exposed and non
exposed tumor tissue, but various studies identified subsets of genes involved in thyroid
carcinogenesis and their related signalling pathway regulations.
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Table 7.2
Overview of conducted gene expression studies in the Ukrainian cohort
Author[ref.]

Hypothesis

Transcriptome

Pathway

2500 genes
differentiallyexpressed inrelation to 131I
dose

AJAP1, FAM38A, CA12,
Cell cycle & growth anddifferentiation, Cell adhesion, LMO3, ZNF493,
Microenvironment/metabolic MTA1, SLC19A1, CDK12,changes, Transcription factor ACVR2A, GALNT7,
and DNA modification through SLC43A3
methylation ; w/o significant
enrichment of a certain
pathwaydifferetial
Delys et gene expression
expression ofal., 2007 is differentially
44.5% of genes[94]
regulated insporadic/radiation- on the array
induced PTC
compared tonormal thyroid

Immune response, Cytokine
ANXA1, CDH3, CLDN1,
activity, Chemokine activity,
DUSP5, GPX1, HMGA2,
Thyroid hormone generation, NELL2, NRCAM, SLIT1,
EGFR signaling pathway,
THBS2, TNC, BCL2, EGR1,
Activation of JNK activity , MAP EGR2, FLRT2
kinase phosphatase activity,
Extracellular matrix, Peptidase
activity, Protease inhibitor
activity, Laminin complex,
Collagen, Cell–cell adhesion,
Integrin complex; p-values
below 0.05

Detours radiation-signature no separation
et al.,in post-Chernobyl of radiation2005 [89] childhood PTC
induced fromsporadic PTC

n/aradiation-induced andsporadic datasets show ahigh correlation

Detours radiation-signature similar between
et al.,in post-Chernobyl radiation2007 [90] childhood PTC
induced andsporadic;n/a

two subsets of 256 and 118
genes separate radiationinduced from sporadic;

homologous recombination

XRCC2, SHFM1, RAD51C,
MUS81, RAD51L1, RAD51,
RAD50, RAD54B, RAD54L,
NBS1, RAD52, XRCC3,
BRCA1

Abend et dose-responseal., 2012 relationship[103]
between 131I
dose and gene
expression

Genes

Dom et radiation-signature separation ofal., 2012 in post-Chernobyl normal exposed[93]
childhood PTC
from normal not
exposed tissue

403 gene signature
Chronic myeloid leukaemia,
Neutrophin signalling pathway,
MAPK signalling pathway,
Insulin signalling pathway,
Renal cell carcinoma, Pancreaticcancer, Regulation of actin
cytoskeleton, Spliceosome,mTOR signalling pathway,
Apoptosis, Focal adhesion

Stein et gene expressionn/aal., 2010 changes in[62]
radiation-induced
childhood PTC in
comparison to thematching normal
tissueCancer, Cellular Growth andProliferation, Reproductive
System Disease, Cellular
Movement, Cell-to-Cell
Signaling, and Cell-MediatedImmune Response

LRP4, IGSF1, ODZ1, CITED1,
SLIT1,HMGA2, SERPINA1,
KCNJ2, AGR2, TACSTD2,
NELL2, CHI3L1, TPO, TFF3,
CRABP1, COL9A3, MATN2,SLC4A4, DIO1, KIT, CCL21,
FBLN1, FHL1, MPPED2

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Detours et al. [89] performed Micromax Microarray experiments to evaluate the gene
expression profile of twelve post-Chernobyl PTCs. In addition, eight sporadic PTCs andthirteen autonomous adenomas from Belgium, France and the US were arrayed. The
group was interested whether the gene expression pattern of the radiation exposedcases would reveal a radiation-related signature and applied several unsupervisedand supervised analyses to the obtained microarray data. Unsupervised hierarchicalclustering was able to distinguish between PTCs and adenomas, but could not separate
the sporadic from the post-Chernobyl PTCs. Similarly, RET/PTC rearrangement was nota criterion which could separate the PTCs into two groups. Significance analysis of
microarray (SAM) found 168 genes to be differentially expressed between adenomas and
PTC with a false discovery rate (FDR) of 1%. Amongst these, a signature of six genes wascapable of accurately differentiating between adenoma and PTC. No such genes were
found when analysing sporadic PTC versus post-chernobyl PTC. Instead, a significant
correlation of the two groups was found which could not be seen for the adenomas. This
correlation was independent from the methods used and was validated in silico using
PTC data from Affymetrix microarrays. Patients were not matched on age, residency, or
sex within this study. Surprisingly, despite the high variation in the clinical parameters of
the patients, the data correlated significantly and indicated a similarity between sporadic
and post-Chernobyl cases. The data suggested that no molecular expression signature
for radiation-induced thyroid cancerogenesis exists.
Two years later the same group [90] repeated the analysis on Agilent microarrays, which
support a broader range of genes. The Ukrainian cohort of twelve patients exposed toradiation was compared to a French cohort of 14 patients without known radiation history.
The distribution of histological subtypes was the same in the two groups. Frequencies of
RET/PTC rearrangement and BRAF mutation were also comparable. Screening for global
expression profiles revealed no difference between the French and the post-Chernobyl
PTCs. However, application of a supervised classification algorithm identified a subset
of genes which was capable of distinguishing French and post-Chernobyl tumors withan error rate of 12%. In further experiments in vitro the same authors showed that 200
mM H2O2 (peroxide) or 2.5 Gy γ-radiation cause a similar transcriptional response in a B
lymphocyte cell line with a subset of 293 genes having a fold change greater than 1.5. 118
out of these genes were also able to separate the French and the post-Chernobyl cohort
with an error of 15%. This implies that peroxide had a major influence in carcinogenesis
in the French cohort. H2O2 is a byproduct of thyroid hormone synthesis and known for its
high DNA damaging potential due to its oxidizing properties. H2O2 is considered as a highly
reactive oxygen species, and free radicals were shown to cause cancers in the thyroid of
Tg-a1BAR mice [91]. Similarly, ionizing radiation is creating reactive oxygen through theradiolysis of water, which is highly abundant in the cellular environment. The etiologicalagents peroxide and radiation both create reactive oxygen species as a cancer initiating
event which supports the finding of similar global gene expression profiles. An additionalsignature of thirteen genes involved in homologous recombination was able to distinguishthe two cohorts with an error rate of 15%. The authors matched the groups on clinicalparameters such as morphology and known molecular aberrations. However, they did not
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match on age and residency, two independent confounders known to affect data analysis.
It would also have been interesting to see whether the magnitude of RET/PTC or BRAF
expression had an influence on the gene expression profile as described in literature [92],but such data was not provided.
A more recent study again tried to address the question whether a radiation-specificsignature is detectable in post-Chernobyl thyroid cancer. Dom et al. [93] chose a carefully
selected cohort. 22 patients who were exposed to radiation and born before April 1986
were matched on age and residency in Ukraine to 23 patients born after March 1987 andhence not exposed to radiation. The cases were subjected to Affymetrix microarrays andexpression of single genes was validated using qRT-PCR.
The authors searched for global gene expression variations using hierarchical clusteringand principal components analysis which successfully separated tumor from normal thyroid.
However, similar analyses were not able to reveal any differences between exposed andnon exposed cases. A subset of eight genes was selected according to known involvementof their products in carcinogenesis: carbonic anhydrase 12, BH3-interacting domain deathagonist, clusterin, cyclin D2, trefoil factor 3, low-density lipoprotein receptor-related
protein 1B, dual specificity phosphatase 1 (DUSP1) and thrombospondin, type I, domaincontaining 7A, and validated by qRT-PCR. All of them were found to be differentiallyregulated in tumor versus normal thyroid tissue.
Supervised analysis of the data could not distinguish exposed from non exposed
tumors either, but the normal tissue seemed to have differential gene expression in bothgroups.
Potential confounding factors such as the clinical parameters sex, age at operation,
patients’ place of residence (region/oblast) at the time point of the Chernobyl accident,
morphological subtype of PTC, TNM classification, presence of BRAF mutations or RET/
PTC rearrangements, tumor size and methodological parameters such as batch effects of
microarray hybridisation or RNA storage time were analysed. The age at operation andthe time of storage of frozen tissue prior to RNA extraction were found to be associatedwith the radiation exposure, and data was adjusted accordingly. The corrected data wasevaluated using SAM and a signature of 403 genes was found to distinguish exposed fromnon exposed normal thyroid tissue. All of them were upregulated in the exposed normal
tissue. The results were validated in silico using an external data set. Gene ontology and
KEGG analysis of the gene signature in DAVID found pathways with an impact on cancer
development and proliferation, mainly MAPK, insulin and mTOR signalling pathways, andenrichment of cell adhesion-related genes.
Thus, the study was not able to show any differences between exposed and non
exposed tumors, but the matching contralateral normal tissue in these patients reveals
significant differences. This could be related to the character of the tumor which is known
to evolve into diverse subpopulations, whereas the surrounding normal tissue does not
evolve but may keep a tumor-initiating expression profile. However, such hypotheses
remain speculative and require validation in an independent set of cases. The signature
identified could be used to classify a PTC cohort in the two categories - exposed and non
exposed, but was associated with a false positive rate of 30%.
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Pathway regulation
Although scientists could not detect a clear radiation-related signature in postChernobyl childhood PTC, with the methods used, the collected data highlighted certain
signalling pathways in exposed over unexposed tumor tissue. The point mutations andgene rearrangements observed in PTC stress out a major role for the MAPK pathway inthyroid tumorigenesis. BRAF mutations and RET as well as NTRK rearrangements lead toconstitutive activation of these genes and are supposed to interfere with their downstream
partners perturbing the pathway cascade. Expression status of other genes - especially inpost-Chernobyl PTC - was rarely explored. The study of Delys et al. [94] aimed to identify
certain signalling pathways and their regulation in relation to the physiopathology ofthe disease. 12 PTCs from Ukrainian patients which were exposed to radiation and 15
sporadic PTCs from French patients plus matching normal tissues were arrayed on Agilent
cDNA microarrays. The statistical algorithm Significance Analysis of Microarray (SAM) wasapplied, and it was possible to significantly distinguish a characteristic gene expression
profile for PTC from normal thyroid tissue. The differences in gene expression may relate
to the observed differences in morphology between tumor and normal tissue. To identify
individual differentially regulated genes, the data was correlated with two independent
PTC data sets [95,96]. Only genes which show the same regulation in at least two of thedata sets were selected for further pathway regulation studies. This resulted in a profile
of 451 up- and 233 downregulated genes. Eleven upregulated genes (ANXA1, CDH3,
CLDN1, DUSP5, GPX1, HMGA2, NELL2, NRCAM, SLIT1, THBS2, TNC) and four downregulated
genes (BCL2, EGR1, EGR2, FLRT2) identified in the microarray data sets were validated by
qRT-PCR. Additionally, 20 genes were already identified in the literature to correlate withthe phenotype of sporadic thyroid cancer [97]. GO term analysis with DAVID revealeda participation of the genes in the gene list in eleven pathways with a p value <0.05.
Many of the pathways are related to the immune response which may more reflect the
infiltration of immune cells into the tumor rather than changes in the tumor cell itself.
Alteration of cytokines and chemokines was observed in this study as well, which isconsistent with other studies where PTC is known to evoke a chronic inflammation invivo and in vitro [98]. This could have a direct influence on the recruitment of lymphatic
cells into the tumor tissue.
Surprisingly, no deregulation of the MAPK pathway could be found, which would be
expected for PTC because of the BRAF mutations and RET/PTC gene rearrangements whichlead to a constitutive expression of those genes. On the other hand, EGF signalling, anactivator of the MAPK pathway, was significantly altered, whereas ERK specific inhibitorsof the DUSP family were highly overexpressed as well. c-jun N-terminal kinase (JNK) and
p38 pathway was another gene cascade significantly altered. Its involvement in thyroid
carcinogenesis was already suggested previously by immunohistochemical detection intumor but not normal thyroid tissue [99]. Also, overexpression of proteases and proteaseinhibitors which are known for remodelling of the ECM was highly abundant in PTC versus
normal tissue. This is a well known cancer initiating event and documented to have aparticipation in thyroid cancer [100,101].
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Cell migration is another mechanism playing an important role in carcinogenesis. Itsconsequences for tumor development can be observed and are described histopathologically[102]. Delys et al. [94] identified several genes from the integrin, cadherin and claudin family
being deregulated in the tumor tissue, which could have a direct influence on the invasive
behaviour of the tumor. It would be interesting to apply a principal component analysis tothese 26 cases of the study to see whether clinical parameters match with these findings,
and tumors with a higher invasive behaviour consistently show a stronger upregulation ofthese pathways.
The study could identify a clear difference between PTC and normal tissue and foundmany pathways which are known to be involved in tumor development being differentiallyregulated. The study could not distinguish between radiation-induced and sporadic
tumors, suggesting that the etiologic agent may be responsible for tumor initiation but
has no influence on tumor progression.
Transcriptomic profiles and radiation dose
Previous studies showed that, especially in gene expression analysis, the use of differing
methods and statistical evaluation algorithms, the sample size and/or selection of control
populations lead to inconsistent findings between studies. These factors may havecontributed to the conclusion that neither a radiation-specific signature nor a gene regulation
mechanism is present in the Ukrainian post-Chernobyl PTC cases. Despite this, a more recent
study performed by Abend et al. [103] aimed to address the question whether a dose-related
response to 131I is present and detectable. The patients included in this study were enrolled in
the Ukraine-American Cohort Study. The patients were all below 18 years old at the time of
accident and individual 131I measurements were taken within two months after the accident[104]. 63 tumor/normal pairs were split in a screening set with 32 cases for Agilent oligo
microarray gene expression analysis and a validation set with 31 cases for qRT-PCR validationof altered genes. Arraying found 2500 genes that were significantly differentially expressed
between the tumor and the normal tissue, but none of the p values survived multiple testing
using false discovery rate (FDR). 75 genes were selected based on analysis of a dose-dependent
differential expression, and this list includes also genes with evidence from previous studies.
qRT-PCR found 11 of those genes were differentially expressed in tumor but not in normal
tissue in relation to the dose received. Nine of the eleven genes are involved in the pathways
cell adhesion (AJAP1, FAM38A), energy metabolism (CA12), transcription or DNA methylation(LMO3, ZNF493, MTA1, SLC19A1), and growth/differentiation (CDK12, ACVR2A). These pathways
are known for their participation in the cellular response to ionizing radiation [105, 106]. The
importance of five genes (CA12, GALNT7, LMO3, SLC43A3 and FAM38A) was also confirmed byothers in post-Chernobyl and other radiation-induced childhood thyroid tumors [62, 107].
The differential expression of the genes is dose-dependent and linear, however, the three
genes SLC19A1, SLC43A3 and ZNF493 exhibit some non-linearity. The cellular response toradiation is known to be non-linear, and changes over time with an early response to DNA
damage and a later survival with chromosomal rearrangements [108,109], and the nonlinearity in differential expression may reflect this. Taken together, the eleven genes show
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a clear difference in expression levels between exposed tumor and exposed normal tissue,
and further studies on the genomic architecture of these genes will give more insight on
their ability to serve as biomarkers for radiation exposure.
In the most recently reported study using material from the patients enrolled in the
Ukrainian-American cohort, Leeman-Neill et al. [110] hypothesized that chromosomal
aberrations such as RET/PTC and point mutations have different associations with 131I
dose. The case series included 26 males (42%) and 36 females (58%) who were resident
in the areas surrounding Chernobyl, i.e., the Zhytomir (n= 17; 27.4%), Kiev (n=12; 19.4%),
or Chernigov (n=33; 53.2%) regions (oblasts), and who were between 5 months and 17
years old (mean 8.0 years) at the time of the Chernobyl accident. The estimated 131I dose forpatients in the study ranged from 0.008 Gy to 8.6 Gy, with a mean dose of 1.3 Gy. Surgicalremoval of PTCs occurred between October 1998 and December 2007, with time between
exposure and surgery ranging from 12.5 to 21.6 years (mean: 16.5 years).
RET/PTC rearrangement was the most common genetic alteration and was found in 22(35%) cases, including 14 RET/PTC1 and 8 RET/PTC3 rearrangements. Point mutations in
the BRAF and RAS genes were found in 9 (15%) and 5 (8%) of the tumors, respectively. All 9
BRAF mutations were BRAFV600E. Four RAS mutations were detected in NRAS codon 61 and 1
in HRAS codon 61. No KRAS mutations were found in codons 12 and 13. In addition, thesetumors were studied for PAX8/PPARγ rearrangement, a prototypic genetic alteration foundin follicular thyroid carcinoma that occurs with lower prevalence in the follicular variant of
PTC. Two tumors were positive for PAX8/PPARγ; both were of the follicular variant of PTC.
In both cases, the fusions were between exon 9 of PAX8 and exon 1 of PPARγ, with several
expected splice variants of the chimeric PAX8/PPARγ transcripts detected. One tumor had
more than 1 mutation, harbouring an NRAS point mutation in codon 61 and PAX8/PPARγ
rearrangement. Twenty five (40%) tumors revealed none of the studied mutations. Patientswith BRAF or RAS mutations had the lowest dose (0.27 Gy and 0.20 Gy, respectively).
RET/PTC1 and RET/PTC3 were associated with a higher dose of 1.04 Gy and 1.54 Gy. The
highest dose of 1.97 Gy had tumors without any of the observed aberrations. There wasalso a significant correlation with the age of the patients, where BRAF and RAS mutations
associated with older age and RET/PTC rearrangements with younger onset. Hence, it isdifficult to differentiate between the known effects of age at diagnosis on the molecular
phenotype of PTC, and the effects of dose, especially in such a small study. The cohort was
not age matched or subdivided between children and adolescents (aged <19) and young
adults (aged >19) at surgery. Children have been shown to receive a relatively higher doseof radiation due to the smaller size of their thyroid.
Interestingly, there was a positive correlation of the chromosomal rearrangements withresidency in the Zhytomir oblast, where the individuals also received a higher radiation
dose. This oblast is known for a moderate iodine deficiency. As such a deficiency was shown
to be a risk factor for thyroid cancer in a Belarussian cohort of post-Chernobyl thyroids[111], the authors suggest a similar contribution for their findings.
Further whole genome studies on cohorts matched for the confounders in this study(age, sex, region of residence) would be required to convincingly link the findings in thispaper and that by Abend et al. [103] to dose of radiation.
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In summary, it is now accepted that the initial studies suggesting that post- Chernobyl
thyroid cancers showed a higher frequency of involvement of the RET/PTC oncogene were
misinterpreted due to the lack of appropriate age-matched controls. It had been assumed
that the molecular pathology of thyroid cancer was not influenced by age, but as thestudies reported above have shown, young onset PTC shows very different pathology andmorphology when compared with the same disease in adults. Studies using the newer“omic” technologies have suggested that there may be subtle differences between PTCs of
a radiation aetiology compared with age-matched controls, but all of these studies require
validation in separate cohorts of patients. The studies so far performed on the effect ofinherited, germline polymorphisms suggest, as with their somatic counterparts, that there
is little to differentiate radiation associated PTC from sporadic PTC. Attention is now turning
to studies on potential epigenetic differences (miRNA and DNA methylation), and to next
generation sequencing technologies to tease out more subtle differences associated witha radiation aetiology. Regardless of the final conclusions of these studies regarding therelationship between radiation and molecular phenotype, the Ukrainian cases provided
to the general scientific community through the generosity of Ukrainian patients and thestaff at the Institute of Endocrinology and Metabolism in Kiev, have been instrumental inincreasing our knowledge of molecular pathology of thyroid cancer in general, and PTC in
particular. It remains to be seen whether any of the data so far generated by these studies,and those yet to come, will lead to the development of better prognostic markers forthyroid cancer. Unlike many cancers, PTC has a releatively good prognosis, with a predicted
death rate over 30-50 years of 1%. Despite this, there is a recurrence rate of 30% [112].
Identification of prognostic biomarkers, combined with clinical features would therefore
aid patient stratification for follow-up.

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Conclusion

The present publication summarizes the results of numerous anddiverse studies of thyroid cancer in children and adolescents of Ukraine
affected as a result of the Chernobyl accident. We specifically have been
focusing on long-term studies on reconstruction of individual thyroid
doses, the relationship of thyroid cancer incidence with the age andplace of residence of children at the time of the accident, clarificationof changes in the structure and invasive properties of “Chernobyl”
papillary thyroid carcinoma (PTC) in different age groups and indifferent periods after the Chernobyl accident, analysis of differencesin the structure and invasive properties of radiogenic and sporadic
PTC, and initial steps of the search for an association of individual
molecular-genetic abnormalities with thyroid exposure dose. It is
anticipated that further progress in discovery of radiation exposure
markers or signatures will involve new advanced technologies, inparticular, the whole genome analysis by next generation sequencing
aimed at identification of possible genetic alterations unknown today
which may underlie the development of radiogenic thyroid cancers.
We express a hope that this book will be useful to the readers
professionally working in different fields of knowledge including
radiation medicine, dosimetry, epidemiology, endocrinology,
oncology, pathology, and molecular biology. The book may also
be of interest to our Japanese colleagues in the analysis of healthconsequences of the accident at Fukushima Dai-ichi Nuclear Plant
where a large-scale ultrasound thyroid screening in young populationof Fukushima prefecture was initiated shortly after the disaster inMarch 2011.
The Аuthors

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