Second primary cancer following adjuvant chemotherapy, radiotherapy and endocrine therapy for breast cancer: a nationwide survey on 47,005 Japanese patients who underwent mastectomy from 1963-1982.

Out of a total of 47,005 cases of primary breast cancer with curative surgery recorded in Japan in the 20 year period from 1963 to 1982, 764, or 1.6 per cent had a second primary cancer occurring during the same period. The distribution of the second site was gastric cancer in 200 (26.2 per cent), breast cancer in 200 (26.2 per cent), colorectal cancer in 59 (7.7 per cent), cancer of the cervix uteri in 54 (7.1 per cent) and thyroid cancer in 37 (4.8 per cent). The gastric cancer was the Borrmann type 4, and the poorly differentiated scirrhous type. Incidence of the second cancer was enhanced, in the first period before 1971 and by contrast, in the second period after 1971 it was diminished. In the chemotherapy (+) group, the occurrence of the second cancer seemed to be strongly influenced by mitomycin C. In the radiotherapy prescribed group, leukemia was as frequent as esophageal cancer, and in those given endocrine therapy, breast cancer strongly inhibited the current one.