BRCA1 and breast cancer: BRCA1 or BRCA2 mutations are associated with high penetrance rates; the estimated mean cumulative risks for breast cancer by age 70 years for BRCA1 and BRCA2 mutation carriers, as reported by a meta-analysis, were 57% (95% CI, 47% to 66%) and 49% (95% CI, 40% to 57%), respectively (8).