It was estimated from their family histories that carriers in this setting are at about six times the general population risk (95% CI, 2-17; P = 0.01), equivalent to a breast cancer risk of 40% by age 70 years (95% CI, 17-77), which is comparable to the 45% estimate found for BRCA2 mutation carriers in a large study of unselected carrier families [34]. This evidence concerns the gene BRCA2 and breast cancer.