The influence of family history of cancer, irradiation and anticancer medication (mitomycin C), on the occurrence of multiple primary neoplasms with breast cancer

The influence of family history of cancer, radiation therapy and anticancer drug therapy (mitomycin C) on the occurrence of multiple primary neoplasms, following treatment of a first primary cancer of the breast, was analyzed by the person-year method in 1,359 patients, in Japan. During 14,371.8 person-years of observation, 111 multiple primary neoplasms including bilateral breast cancers were found in 109 patients. The incidence rate of multiple primary neoplasms were 0.00772 per person-year. The incidence in patients with a family history of cancer was 1.29 times greater than that in patients without such a family history, and the incidence in patients with a family history of breast cancer was about three times greater than that in those without it (p < 0.01). Radiation therapy raised the occurrence of subsequent primary neoplasms 1.28-fold (or 1.62 fold after 5 years), and mitomycin C (a total dose of 0.8 mg/kg) therapy caused no increase in the occurrence of subsequent primary cancers, after an observation of 10 years or so. (author)