STUDIES OF CANCER AND RADIATION-DOSE AMONG ATOMIC-BOMB SURVIVORS - THE EXAMPLE OF BREAST-CANCER

A comprehensive program of medical follow-up of survivors of the atomi c bombings of Hiroshima and Nagasaki, Japan, by the Radiation Effects Research Foundation (RERF) has produced quantitative estimates of canc er risk from exposure to ionizing radiation. For breast cancer in wome n, in particular, the strength of the radiation dose response and the generally low level of population risk in the absence of radiation exp osure have led to a clear description of excess risk and its variation by age at exposure and over time following exposure. Comparisons of R ERF data with data from medically irradiated populations have yielded additional information on the influence of population and underlying b reast cancer rates on radiation-related risk. Epidemiological investig ations of breast cancer cases and matched controls among atomic bomb s urvivors have clarified the role of reproductive history as a modifier of the carcinogenic effects of radiation exposure. Finally, a pattern of radiation-related risk by attained age among the survivors exposed during childhood or adolescence suggests the possible existence of a radiation-susceptible subgroup. The hypothetical existence of such a g roup is lent plausibility by the results of recent family studies sugg esting that heritable mutations in certain genes are associated with f amilial aggregations of breast cancer. The recent isolation and clonin g of one such gene, BRCA1, makes it likely that the hypothesis can be tested using molecular assays of archival and other tissue obtained fr om atomic bomb survivor cases and controls.