OVERESTIMATION OF HEREDITARY BREAST-CANCER RISK

Objective To find out how women with breast or ovarian cancer rate the ir chances of carrying hereditary factors for these cancers and to det ermine the extent to which they overestimate their risk. Summary Backg round Data BRCA1 and BRCA2 are genes that cause breast and ovarian can cer when they are inherited in families. Testing for disease-associate d mutations in these genes is now available commercially. Previous stu dies have shown that women overestimate their chances of carrying muta tions. However, women's perceptions of risk have not been compared to objective estimates or to actual BRCA1 and BRCA2 testing results. Meth ods This study examines estimates of carrying BRCA1 and BRCA2 mutation s among women participating in a randomized trial comparing alternativ e precounseling educational materials. Estimates were provided by part icipants in a baseline mailed survey. Estimates given by participants were compared to those given by an expert panel and by a statistical m odel. Testing was offered free of charge and was done in an academic l aboratory using standard techniques. Baseline estimates of participati ng women were compared to the estimates of the expert panel, to the ca rrier probability provided by the statistical model, and to actual tes ting results. Results Women who have a personal history of breast or o varian cancer significantly overestimate their risk of carrying heredi tary factors for breast and ovarian cancer. Self-estimates exceeded th e estimates of experts and a statistical model. One hundred women comp leted testing, and 21 mutations in BRCA1 or BRCA2 were found. Many tes t-negative women also overestimated their hereditary risk. Some women with a high carrier probability were negative for BRCA1 and BRCA2 muta tions. Conclusions Overestimation of hereditary factors is common amon g affected women with a family history of cancer. Pretest education an d counseling should reduce these high-risk perceptions. Better estimat es of carrier probability will direct more intensive clinical services and research.