E. Cancers other than Leukemia

Review of Thirty Years Study of Hiroshima and Nagasaki Atomic Bomb Survivors II. BIOLOGICAL EFFECTS

Abstract

Because latent periods are sometimes long, and many cancers appear only late in life, the catalogue of cancers induced by the whole body exposure of the A-bomb survivors to ionizing radiation is still growing. Tumors for which present evidence is compelling include, in addition to leukemia, cancers of thyroid, female breast, and lung. Others for which an associatation may soon be established are cancers of the salivary gland and stomach cancer. Cancers which are unlikely to appear among atomic bomb survivors in excess of natural incidence include skin cancer and bone cancer, as these appear to require for their initiation doses that are incompatible with life if administered on a whole body basis. Although chronic lymphocytic leukemia continues to provide an important exception, and for many sites of cancer there is not yet evidence that radiation has increased incidence above normal levels, the data on A-bomb survivors are otherwise consistent with the hypothesis that the carcinogenic effect of ionizing radiation is general, involving all tissues.
Studies of cancer among A-bomb survivors are notably limited with respect to the influence of variables other than dose, age, sex, and time. It seems highly desirable that other risk factors be studied in conjunction with radiation dose and demographic variables in an effort to detect interactions that might provide clues as to the etiology of cancer and as to the mechanisms by which ionizing radiation produces cancer.
Provisional estimates suggest that the absolute risk of cancer, in terms of excess cases per 10⁶ person-year rads (T65 dose) are about 1.6 for leukemia, 1.2 for thyroid, 2.1 for breast and 2.0 for lung, when estimation is based on age-ATB groups that have demonstrated these effects. A great deal of additional work will be required to provide definitive information on the quantitative aspects of dose-response over time, including the biological effect of gamma radiation relative to that for neutrons.