Technical Report No. 13-86
Lung cancer, radiation, and smoking among A-bomb survivors, Hiroshima and Nagasaki
Kopecky KJ, Nakashima E, Yamamoto T, Kato HSummary
The effects of exposure to ionizing radiation and of smoking on the incidence of lung cancer in a cohort of Japanese atomic bomb survivors were investigated. A total of 351 cases occurred among 29,332 exposed survivors for whom both smoking data (from surveys conducted during 1963-71) and radiation dose estimates were available; 219 of these diagnoses were based on some form of histopathologic examination, and 157 were confirmed by the present investigators. The excess relative risk (ERR) of lung cancer was modeled as a sum of two components: 1) a radiation-related ERR that increased with decreasing age at the time of bombing, and 2) a smoking-related ERR that increased with daily cigarette consumption, as measured at the beginning of follow-up, and with attained age. There was no significant interaction between the effects of radiation exposure and smoking (p=.72), suggesting that the two factors may combine to increase the relative risk (RR) of lung cancer in an additive rather than multiplicative fashion. Adjustment for the effect of smoking by means of this additive RR model substantially reduced apparent sex differences in both the radiation-related RR and in the background rates of lung cancer, since few women and most men were smokers. Small cell carcinoma displayed somewhat greater sensitivity to both radiation and smoking than did adenocarcinoma or epidermoid carcinoma; however, the variation between the histology-specific RR functions was not statistically significant.
The effects of exposure to ionizing radiation and of smoking on the incidence of lung cancer in a cohort of Japanese atomic bomb survivors were investigated. A total of 351 cases occurred among 29,332 exposed survivors for whom both smoking data (from surveys conducted during 1963-71) and radiation dose estimates were available; 219 of these diagnoses were based on some form of histopathologic examination, and 157 were confirmed by the present investigators. The excess relative risk (ERR) of lung cancer was modeled as a sum of two components: 1) a radiation-related ERR that increased with decreasing age at the time of bombing, and 2) a smoking-related ERR that increased with daily cigarette consumption, as measured at the beginning of follow-up, and with attained age. There was no significant interaction between the effects of radiation exposure and smoking (p=.72), suggesting that the two factors may combine to increase the relative risk (RR) of lung cancer in an additive rather than multiplicative fashion. Adjustment for the effect of smoking by means of this additive RR model substantially reduced apparent sex differences in both the radiation-related RR and in the background rates of lung cancer, since few women and most men were smokers. Small cell carcinoma displayed somewhat greater sensitivity to both radiation and smoking than did adenocarcinoma or epidermoid carcinoma; however, the variation between the histology-specific RR functions was not statistically significant.