Overestimation of Hereditary Breast Cancer Risk

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Abstract
To find out how women with breast or ovarian cancer rate their chances of carrying hereditary factors for these cancers and to determine the extent to which they overestimate their risk. BRCA1 and BRCA2 are genes that cause breast and ovarian cancer when they are inherited in families. Testing for disease-associated mutations in these genes is now available commercially. Previous studies have shown that women overestimate their chances of carrying mutations. However, women's perceptions of risk have not been compared to objective estimates or to actual BRCA1 and BRCA2 testing results. This study examines estimates of carrying BRCA1 and BRCA2 mutations among women participating in a randomized trial comparing alternative precounseling educational materials. Estimates were provided by participants in a baseline mailed survey. Estimates given by participants were compared to those given by an expert panel and by a statistical model. Testing was offered free of charge and was done in an academic laboratory using standard techniques. Baseline estimates of participating women were compared to the estimates of the expert panel, to the carrier probability provided by the statistical model, and to actual testing results. Women who have a personal history of breast or ovarian cancer significantly overestimate their risk of carrying hereditary factors for breast and ovarian cancer. Self-estimates exceeded the estimates of experts and a statistical model. One hundred women completed testing, and 21 mutations in BRCA1 or BRCA2 were found. Many test-negative women also overestimated their hereditary risk. Some women with a high carrier probability were negative for BRCA1 and BRCA2 mutations. Overestimation of hereditary factors is common among affected women with a family history of cancer. Pretest education and counseling should reduce these high-risk perceptions. Better estimates of carrier probability will direct more intensive clinical services and research.