Analysis of Cancer Mortality among Atomic Bomb Survivors in Hiroshima Prefecture, 1968-1997

The Research Institute for Radiation Biology and Medicine has a cohort of atomic bomb survivors, residents of Hiroshima Prefecture, followed up since 1968. An epidemiological project on cancer mortality has been extended by the 5 years from 1992 to 1997. In this paper we aim to evaluate the relative risk pattern of specific cancers by radiation dose over time and during this recent 5 years. We obtained the late effects and temporary changes from cancer sites on mortal ity such as leukemia, all cancers except leukemia, and cancers of the lung, esophagus, liver, stomach, colon, pancreas, breast and uterus. Although results for the additional 5 years were not statistically significant due to the relatively small sample size, we observed decreasing trends for many cancer sites including all cancers except leukemia, esophagus, colon, stomach, liver and breast cancers. In particular the sharply increased excess relative risk for female breast cancer shown in 1988-1992 dramatically declined during the period 1993-1997.