Aggregation of ovarian cancer with breast, ovarian, colorectal, and prostate cancer in first-degree relatives.

Epidemiologic studies have demonstrated a tendency for common cancers to aggregate in families. The authors investigated the effects of family history of cancer at multiple sites, including the breast, ovary, colorectum, and prostate, on ovarian cancer risk among 607 controls and 558 ovarian cases in Hawaii and Los Angeles, California, in 1993-1999. A family history of cancer of the breast, ovary, colorectum, or prostate in first-degree relatives was associated with an increased risk of ovarian cancer (odds ratio (OR)=1.7, 95% confidence interval (CI): 1.1, 2.6; OR=3.2, 95% CI: 1.3, 7.9; OR=1.5, 95% CI: 0.9, 2.5; and OR=1.6, 95% CI: 1.0, 2.8, respectively). A greater risk of ovarian cancer was observed for women with parents rather than siblings with a history of breast or prostate cancer and for women with parental colorectal cancer diagnosed at an early age, suggesting a genetic predisposition among these women. The risk of nonmucinous tumors, but not mucinous tumors, was positively associated with a family history of cancer. No significant interaction effects on risk existed between oral contraceptive pill use or pregnancy and family history of breast and/or ovarian cancer. Study findings suggest that ovarian cancer aggregates with several common cancers in family members.