Abstract
Purpose: The Radiation Effects Research Foundation has reported that there is radiation risk for basal cell carcinoma based on pathological examination and follow–up of radiation and skin cancer incidence through 1987 of the Life Span Study (LSS) cohort comprising atomic bomb survivors. In this study, we extended the follow up by 10 years, reexamining radiation risk for skin cancer by histological type.
Method: Of 120,321 LSS members, 80,158 who were in the city of Hiroshima or Nagasaki at the time of bombing and with radiation dose estimated by the DS02 dosimetry system were examined. Pathologists reviewed suspected skin cancer cases diagnosed between 1958 and 1996, and confirmed first primary skin cancers. Excess relative risks (ERRs) of skin cancer due to radiation by histological type were estimated using Poisson regression model.
Results: Among the eligible LSS population, 336 incident skin cancer cases were observed. By histological type, the following cases were observed: malignant melanoma (n = 10), basal cell carcinoma (n = 123), squamous cell carcinoma (n = 144), Bowen’s disease (n = 64), Paget’s disease (n = 10), and other skin cancer cases (n = 15). ERRs were estimated assuming a linear dose response, and only basal cell carcinoma had a statistically significant positive dose response (ERR/Gy = 2.1, 95% confidence interval (CI) = 0.37-1.2, P<0.01), the previous study with follow-up through 1987 reported an ERR/Gy of 1.8 (90% CI = 0.83-3.3). We also explored other models in an effort to find a best fit model using Akaike information criteria (AIC). The best fit dose response model estimated a dose threshold at 0.6 Gy (95% CI = 0.34- 0.89), an ERR/Gy of 2.7 (95% CI = 1.1 - 5.1). This model predicted an ERR at 1 Gy of 1.1 (95% CI = 0.43-2.05). This model provided the risk of basal cell carcinoma increased by 10% with each decrease year of age at exposure.
Conclusion: Epidermal basal cells are sensitive to ionizing radiation, especially for people who were young at exposure. The threshold for a radiation dose response of basal cell carcinoma was estimated to be 0.6 Gy, lower than the 1.0 Gy reported in the previous study.
