Cancer Incidence in Atomic Bomb Survivors. Part II: Solid Tumors, 1958-1987

This report presents, for the first time, comprehensive data on the incidence of solid cancer and risk estimates for A-bomb survivors in the extended Life Span Study (LSS-E85) cohort. Among 79,972 individuals, 8613 first primary solid cancers were diagnosed between 1958 and 1987. As part of the standard registration process of the Hiroshima and Nagasaki tumor registries, cancer cases occurring among members of the LSS-E85 cohort were identified using a computer linkage system supplemented by manual searches. Special efforts were made to ensure complete case ascertainment, data quality and data consistency in the two cities. For all sites combined, 75% of the cancers were verified histologically, 6% were diagnosed by direct observation, 8% were based on a clinical diagnosis, and 12.6% were ascertained by death certificate only. A standard set of analyses was carried out for each of the organs and organ systems considered. Depending on the cancer site, Dosimetry System 1986 (DS86) organ or kerma doses were used for computing risk estimates. Analyses were based on a general excess relative risk model (the background rate times one plus the excess relative risk). Analyses carried out for each site involved fitting the background model with no dose effect, a linear dose-response model with no effect modifiers, a linear-quadratic dose-response model with no effect modifiers, and a series of linear dose-response models that included each of the covariates (sex, age at exposure, time since exposure, attained age and city) individually as effect modifiers. Because the tumor registries ascertain cancers in the registry catchment areas only, an adjustment was made for the effects of migration. In agreement with prior LSS findings, a statistically significant excess risk for all solid cancers was demonstrated [excess relative risk at 1 Sv $({\rm ERR}_{1\ {\rm Sv}})=0.63$; excess absolute risk (EAR) per 104 person-year sievert (PY Sv) = 29.7]. For cancers of the stomach (${\rm ERR}_{1\ {\rm Sv}}=0.32$), colon (${\rm ERR}_{1\ {\rm Sv}}=0.72$), lung (${\rm ERR}_{1\ {\rm Sv}}=0.95$), breast (${\rm ERR}_{1\ {\rm Sv}}=1.59$), ovary (${\rm ERR}_{1\ {\rm Sv}}=0.99$), urinary bladder (${\rm ERR}_{1\ {\rm Sv}}=1.02$) and thyroid (${\rm ERR}_{1\ {\rm Sv}}=1.15$), significant radiation associations were observed. There was some indication of an increase in tumors of the neural tissue (excluding the brain) among persons exposed to the bombs before age 20. For the first time, radia