Scientific Protocol for the Study of Thyroid Cancer and Other Thyroid Disease in Ukraine Following the Chernobyl Accident
Condition: Thyroid Cancer; Non-Cancer Thyroid Disease; Non Thyroid Cancer
MeSH terms: Thyroid Neoplasms; Thyroid Diseases
Study type: Observational

Summary: 
      The nuclear power plant accident at Chornobyl released large quantities of Iodine-131 and
      other radioisotopes of iodine in the atmosphere, contaminating thousands of square kilometers
      and exposing millions of people. For this study, a well-defined subset of Ukrainian children
      aged 0-18 years or in utero at the time of the accident are being identified and examined by
      well-trained specialists for thyroid disease every two years for at least three cycles. The
      study is a collaborative effort of research in Ukraine and the United States.

      The cohort will include approximately 13,000 persons who were children in 1986, all or most
      of whom have had their thyroids measured for radioactivity during the weeks immediately
      following the accident (or whose mothers had measurements taken while the child was in
      utero). Under a rigid research protocol these subjects will receive diagnostic thyroid
      examinations, including palpation, ultrasound scanning, thyroid hormone and other laboratory
      tests, and, if indicated, fine-needle aspiration biopsy. Interview information regarding
      residential, health, diet and lifestyle history will also be collected. All subjects will be
      followed for thyroid cancer morbidity and mortality. Thyroid cancers will be confirmed by
      expert pathology examination of tissue.

      In addition to the analysis of thyroid radiation measurements made in May-June, 1986, efforts
      will be made to reconstruct each person's exposure and to estimate the radiation dose to the
      thyroid. This will involve the reconstruction of deposition patterns and environmental
      pathways of the radioiodines, and of the location, dietary characteristics, and lifestyle of
      each person throughout the exposure period.

      The aim of the study is to carry out valid and credible assessments of the early and late
      morphologic and functional changes in the thyroid glands of persons exposed to radiation from
      radioactive materials released as a consequence of the Chornobyl nuclear power plant
      accident. The emphasis is on dose- and time-specific changes.

      In the course of the study other possible risk factors will be examined including dietary
      iodine intake during and after 1986, and the ingestion of potassium iodide for thyroid
      protection shortly after the accident.
    

Detailed description: 
      The nuclear power plant accident at Chornobyl released large quantities of Iodine-131 and
      other radioisotopes of iodine into the atmosphere, contaminating thousands of square
      kilometers and exposing millions of people. For this study, a well-defined subset of
      Ukrainian children aged less than 18 years or in utero at the time of the accident were
      identified and have been followed up. The main cohort was screened for thyroid disease every
      two years for 4 cycles from 1998 through 2007, with another cycle resumed in 2011(fifth
      cycle), which is now underway. The in utero cohort was screened between 2003-2006 and has
      also been screened since 2011. The study is a collaborative effort of researchers in Ukraine
      and the United States.

      The main cohort includes approximately 13,000 persons who were children in 1986, all or most
      of whom had their thyroids measured for radioactivity during the weeks immediately following
      the accident. Under a rigid research protocol, these subjects receive diagnostic thyroid
      examinations, including palpation, ultrasound scanning, thyroid hormone and other laboratory
      tests (only in the first four cycles). If indicated, they are referred for a fine-needle
      aspiration biopsy. Interview information regarding residential, health, diet and lifestyle
      history has also been collected. All subjects are followed for thyroid cancer morbidity.
      Thyroid cancers are confirmed by expert pathology examination of tissue obtained during
      surgery. The in utero cohort includes a total of 2,582 individuals. In addition starting in
      2003, ~ 7,000 parents of members of the main cohort who were under age 10 y at the time of
      the accident were interviewed in order to increase the accuracy of recall. These individuals
      were listed as new subjects. Altogether, 23,143 individuals have been accrued in this study.

      In addition to the analysis of thyroid radiation measurements made in May-June, 1986,
      radiation dose to the thyroid was estimated drawing on such data as the reconstruction of
      deposition patterns and environmental pathways of the radioiodines, and of the location,
      dietary characteristics, and lifestyle of each person throughout the exposure period. For in
      utero subjects, fetal dose has been estimated based on the mother s thyroid dose.

      The aim of the study is to assess the early and late morphologic and functional changes in
      the thyroid glands of persons exposed at young ages to radiation from radioactive materials
      released as a consequence of the Chernobyl nuclear power plant accident, with emphasis on
      dose-and time-specific changes.

      There have been several amendments to the protocol: transition in 2008 to cancer case
      ascertainment using a passive form of follow-up based on linkage to the National Cancer
      Registry of Ukraine (NCRU) which still continues during thefifth cycle of screening; a
      sub-study involving an additional follow-up examination of those cohort members who were
      diagnosed with benign nodular thyroid pathology during one of the earlier four active
      screening cycles; and genetic studies (gene expression and germline SNP studies) of thyroid
      cancer in this Ukrainian cohort exposed to radioiodines from Chernobyl fallout as children or
      adolescents; and most recently, a pilot study of genomic characterization of thyroid cancers
      (2013).
    

Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Subjects exposed to I131 before the age of 18 years and subjects exposed to I131 in utero
      
Keywords: Cohort; Radiation; In Utero; Genomic