Multiple primary cancers: with reference to atomic bomb survivors in Hiroshima.

We treated 44 patients with multiple primary cancers, at the Second Department of Surgery, Hiroshima University, during the 14 year period from 1968-1981. The total number of malignant tumors was 1,934 during this period, thus the incidence of multiple primary cancers was 2.3 per cent. Nine of the 44 were atomic bomb survivors in Hiroshima and were characterized by the frequent incidence of the second tumor about 30 years after exposure to the atomic bomb. In addition, the second tumor tended to develop later in patients prescribed radiotherapy for the first tumor. As for the site of tumor, there was no tendency of more frequent development of tumors in organs highly sensitive to radiation other than the thyroid.