Multiple primary cancers of the breast and ovary.

Multiple primary cancer of the breast and ovary were investigated as part of a survey being undertaken at the Birmingham and West Midlands Regional Cancer Registry. Population-based data relating to 17,756 registrations for breast and 3470 for ovarian cancer between 1950 and 1964 were analysed. On the basis of person-years at risk and incidence rates for the Region (1960-1962), an increased risk of a second primary tumour in the ovary was observed in patients diagnosed with a first primary in the breast before 45 years of age (O = 8; E = 1.83; P less than 0.001). No excess was found in patients diagnosed after 45 years of age (O = 15; E = 17.06). In patients with an index tumour of the ovary, the observed number of second primary tumours of the breast was not significantly different from the expected number (O = 19; E = 12.95). Complementary analysis (a combined assessment for the 2 sites) showed that the development of a first primary at either site before 45 years of age carried a 2.8-fold risk of a second primary tumour at the other site (O = 9; E = 3.21; P less than 0.01). After 45 years of age no increased risk was found (O = 32; E = 28.63). Over all ages a 1.3-fold risk was observed (O = 42; E = 31.54; P less than 0.05). No evidence of subfertility was found in the 9 patients in the high-risk premenopausal group who developed the 2 tumours. The results are more consistent with an aetiology of early exposure to an external carcinogen than with one of abnormal hormone production.