Familial breast and ovarian cancer risks and BRCA1 germline mutations in two population-based studies

Abstract

9532 Background: A family history of breast or ovarian cancer is related to risk for breast and ovarian cancer and possibly other site-specific cancers, but little is known about specific causes of these associations. Methods: We studied 1978 female first-degree relatives (FDRs) of 670 unselected Caucasian invasive breast cancer cases (probands) recruited to a population-based family study. Probands were administered the same questionnaire. Recruited to a similarly designed study of ovarian cancer, 342 FDRs of 1848 unselected Caucasian ovarian cancer probands also were studied. By extensive mutation testing, 18 breast cancer and 29 ovarian cancer probands were identified as BRCA1 mutation carriers (BRCA1-positive). Standardized incidence ratios were calculated using referent five-year age- and calendar year-specific U.S. cancer incidence rates. Results: Risks of breast and ovarian cancer in female FDRs of BRCA1-positive breast cancer cases were 10.6 (95% confidence interval (CI): 6.0–18.9) and 7.9 (95% CI...