Breast Cancer Risk Estimates for Relatives of White and African American Women With Breast Cancer in the Women's Contraceptive and Reproductive Experiences Study

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Abstract
Purpose Family history is a well-recognized risk factor for breast cancer. Familial aggregation and segregation analyses have estimated breast cancer risk based on family history primarily for white women; such information is limited for African American (AA) women. The purpose of this report is to update breast cancer risk estimates associated with a family history of breast cancer for white and AA women. Methods We used family cancer history from 2,676 white and 1,525 AA women with breast cancer (probands) in the population-based National Institute of Child Health and Human Development's Women's Contraceptive and Reproductive Experiences (CARE) Study to estimate age-specific breast cancer risks in their first degree adult female relatives. Cumulative hazard curves were calculated for relatives of all probands using Cox proportional hazards models, and were stratified by the proband's race and age at diagnosis and number of relatives affected. Results Breast cancer risks for white and AA women with a family history of the disease are similar through age 49 years, but diverge afterwards, with higher risks by age 79 in white women than in AA women (17.5% [SE, 0.9%] v 12.2% [SE, 1.1%]; P < .001). These risks increase as the number of affected first degree relatives increases, reaching 25.2% (SE, 3.4%) and 16.9% (SE, 4.0%) in white and AA women with more than one affected relative, respectively (P = .3). Conclusion We found age-related racial differences in breast cancer risk in women with a family history of breast cancer and have updated risk estimates for white and AA women for clinical use.