Studies of the mortality of A-bomb survivors, report 7. Part III. incidence of cancer in 1959-1978, based on the tumor registry, Nagasaki.

The incidence of malignant tumors in the Radiation Effects Research Foundation (RERF) Life Span Study (LSS) sample in Nagasaki as revealed by the Nagasaki Tumor Registry was investigated for the period 1959-1978. (1) No bias in exposure status in data collection was revealed. Neither method of diagnosis nor reporting hospitals nor the frequency of "doubtful" cases differ by exposure dose. (2) The risk of radiogenic cancer definitely increases with radiation dose for leukemia, cancers of the breast, lung, stomach, and thyroid, and suggestively so for cancers of the colon and urinary tract and multiple myeloma. However, no increase is seen for cancer of the esophagus, liver, gall bladder, uterus, ovary, or salivary gland or for malignant lymphoma. (3) In general, the relative risks based on incidence, that is, on the tumor registry data, are either the same or somewhat higher than those based on mortality in the same years; however, the absolute risk estimates [excess cancer per 10(6) Person Year Rad (PYR)] are far higher. (4) Since A-bomb radiation in Nagasaki consisted essentially of gamma rays, the present report provides a good opportunity to examine the shape of the dose-response curve for gamma exposures. Unfortunately, statistically one cannot actually distinguish one model from another among a simple linear, a quadratic, or a linear quadratic response. Further data are obviously necessary.