BRCA1 and breast cancer: The cumulative risks of breast cancer by age 70 were estimated to be 65% and 45% for BRCA1 and BRCA2 mutation carriers, respectively, in a meta-analysis of population-based studies [1] - as compared with 56 to 80% for BRCA1 and BRCA2 mutation carriers, respectively, in analyses based on families with multiple affected individuals [2-5].