Family history of reproductive cancers and ovarian cancer risk: an Italian case-control study.

The relation between family history of ovarian, breast, and endometrial cancer and risk of epithelial ovarian carcinoma was analyzed within the framework of a case-control study conducted from 1983 to 1989. The study included 755 cases of ovarian cancer and 2,023 controls in hospital for a spectrum of acute nongynecologic, hormonal, or neoplastic conditions in the Greater Milan area, Italy. Eighteen cases (2%) and 24 controls (1%) reported a history of ovarian cancer in a first-degree relative: The corresponding multivariate adjusted odds ratio (OR) was 1.9 (95% confidence interval (CI) 1.1-3.6). The risk of ovarian cancer was elevated in women reporting a family history of breast cancer (OR = 1.6, 95% CI 1.1-2.3), but no significant association emerged with a family history of endometrial cancer (OR = 1.3, 95% CI 0.8-1.7). When the data were stratified by family history of breast cancer, a family history of ovarian cancer was over 10 times more frequent in both cases and controls who reported a family history of breast cancer than in cases and controls reporting no family history of breast cancer. The estimated odds ratio for ovarian cancer associated with a family history of the disease was 2.3 (95% CI 1.1-4.5) in women not reporting a family history of breast cancer, but no association emerged in the subgroup of women reporting a family history of breast cancer. These results confirm that a family history of ovarian cancer increases the risk of the disease, but the percentage of ovarian cancer cases explained by a family history of the disease is small: Less than 1% of observed cases in this study could be attributed to this "family risk factor."