BRCA2 and breast cancer: In one study that prospectively included a cohort of 978 BRCA1 and 909 BRCA2 pathogenic carriers from the United Kingdom, the average cumulative risks by age 70 years for BRCA1 carriers were estimated to be 60% (95% confidence interval [CI], 44%-75%) for breast cancer and 59% (95% CI, 43%-76%) for ovarian cancer.