The impact of family history on ovarian cancer risk. The Utah Population Database.

Objective: To estimate the relative risks and population attributable risks of ovarian cancer associated with family histories of cancer at several sites.
Methods: A matched case-control analytic study (662 cases, 2647 controls), employing the Utah Population Database, a genealogy of approximately 1 million individuals linked to cancer incidence data from the Utah Cancer Registry. Family history was assessed using kinship order and a kinship-weighted familial standardized incidence ratio statistic.
Results: Family histories of ovarian, uterine, breast, and pancreatic cancer were significantly associated with increased risk of ovarian cancer. The relative risk of ovarian cancer was 4.31 (95% confidence interval [CI], 2.35 to 7.90) for women with a first-degree relative with ovarian cancer, 2.12 (95% CI, 1.19 to 3.78) for women with an affected second-degree relative, and 1.48 (95% CI, 0.98 to 2.24) for women with an affected third-degree relative. The odds ratio (OR) was 2.06 (95% CI, 1.44 to 2.93) for those with the highest familial standardized incidence ratio. No age differences were observed between cases with and without a family history of ovarian cancer. There was substantial heterogeneity of family history effects by cell type. Increased parity was not protective among women with a strong family history of cancer at the sites studied (OR, 1.11; 95% CI, 0.38 to 3.26), although it was protective among women without a family history of these cancers (OR, 0.29; 95% CI, 0.11 to 0.62).
Conclusions: The risk of ovarian cancer was substantially increased among women with family histories of ovarian, uterine, pancreatic, and, to a lesser degree, breast cancer. Among women with family histories of any of these cancers, the risk of ovarian cancer is not diminished by high parity.