RERF Report No. 16-12
Paper published in Radiation Research§“Skin Cancer Incidence among Atomic Bomb Survivors from 1958 to 1996”
Hiromi Sugiyama, Munechika Misumi, Masao Kishikawa, Masachika Iseki, Shuji Yonehara,Tomayoshi Hayashi, Midori Soda, Yukiko Shimizu, Ritsu Sakata, Eric J. Grant, Fumiyoshi
Kasagi, Kiyohiko Mabuchi, Akihiko Suyama, Kotaro Ozasa
Radiat Res 2014 (May); 181(5):531–9(doi: 10.1667/RR13494.1)
Study Findings
Researchers observed that exposure to radiation is associated with a significant risk ofdeveloping basal cell skin cancer, with a dose-response threshold of 0.63 Gy and risk increasing
as the age at exposure decreases.
Commentary
1. Objective
Researchers have reported a clearly increased risk of skin cancer, especially basal cellcancer, in association with exposure to ionizing radiation, based on studies of A-bomb survivors,
workers in the field of radiation medicine, and individuals with a history of radiation treatment.
The Radiation Effects Research Foundation (RERF) previously reported radiation risks for skincancer based on cases diagnosed during the period from 1958 to 1987 in the Life Span Study(LSS) population. In the present study, the observation period was extended for 9 years, andradiation risks for skin cancer according to histological type as well as the effects of ultraviolet
radiation on radiation risks were investigated.
2. Methods
The subjects of this study were 80,158 of the 120,321 individuals in the LSS population
who were alive in 1958, when both local cancer registries in Hiroshima and Nagasaki began
operations, and whose radiation dose was estimated by the latest dosimetry system (DS02).
Pathological review was conducted on potential skin tumors diagnosed from 1958 to 1996 toestimate radiation risks for first primary cancers by histological type. A Poisson regression
model was used for the analysis.
3. Results(1) Radiation risks for basal cell cancer
With regard to basal cell cancer (123 cases), the best fit was a linear-threshold model with athreshold dose of 0.63 Gy (95% confidence interval [CI]: 0.32, 0.89); the excess relative risk at 1
Gy of exposure (ERR1Gy) was estimated to be 0.74 (95% CI: 0.26, 1.6) for those age 30 atexposure. The risk was estimated to increase by 11% with each one-year decrease in age atexposure; thus the ERR1Gy was estimated to be about 7 after exposure at age 10. On the otherhand, attained age did not significantly affect radiation risks.
(2) Relationship between ultraviolet radiation and radiation risks for basal cell cancer
The ERR1Gy of basal cell cancer on skin areas likely to be exposed to ultraviolet radiation,such as the face and hands, was estimated at 0.6 (95% CI: <0, 2.1), and the ERR1Gy of areas
unlikely to be exposed to ultraviolet radiation, such as the trunk and extremities except for hands,
was estimated as 2.3 (95% CI: 0.61, 6.7). Although there was no statistically significant
difference between the two (P = 0.15), the results suggest that radiation risks were higher for theareas unlikely to be exposed to ultraviolet radiation.
(3) Radiation risks for squamous cell cancer in situ (Bowen’s disease)
When a linear model was used, the ERR1Gy of squamous cell cancer in situ (64 cases) was
0.71 (95% CI: 0.063, 1.9). However, by city, the ERR1Gy of squamous cell cancer in situ
(Bowen’s disease) in Hiroshima (56 cases) was not significant, at 0.28 (95% CI: <0, 1.9),
whereas that in Nagasaki (8 cases) was extremely high, at 17.6 (95% CI: 3.0, 149); and astatistically significant difference existed between the two (P < 0.001). However, the number ofcases in Nagasaki was small, and there may have been a difference between Hiroshima andNagasaki in the diagnosis of squamous cell cancer in situ and in the rate of reporting to local
cancer registries. Therefore, it was difficult to draw a conclusion about whether any significant
dose-response relationship existed.
(4) Radiation risks for other histological types
There was no significant dose response relationship for malignant melanoma (10 cases),squamous cell cancer (114 cases), Paget disease (10 cases), or other skin cancers (15 cases). The
null result for malignant melanoma with regard to radiation dose is especially notable since thatis the most serious form of skin cancer.
The results of this study show that a linear dose-response relationship with a threshold doseof 0.63 Gy exists between basal cell cancer and A-bomb radiation, and that the lower the age isat exposure, the higher the radiation risk. There was no significant relationship between radiation
exposure and malignant melanoma, squamous cell cancer, or Paget disease.

The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring in
Hiroshima and Nagasaki for more than 60 years. RERF’s research achievements are considered theprincipal scientific basis for radiation risk assessment by the United Nations Scientific Committee on theEffects of Atomic Radiation (UNSCEAR) and for recommendations regarding radiation protection
standards by the International Commission on Radiological Protection (ICRP). RERF expresses its
profound gratitude to the A-bomb survivors and survivors’ offspring for their cooperation in our studies.

2§Radiation Research, which is an official monthly journal of the Radiation Research Society, publishes
original, peer-reviewed papers and review articles on radiation effects and related issues in the fields ofphysics, chemistry, biology, and medicine. (Impact factor in 2013: 2.445)

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