They found an increase in breast cancer risk for BRCA1 mutation carriers who started OC before the age of 20 years (OR = 1.45; 95% CI 1.20–1.75; p = 0.0001) and a non-significant increase for carriers who started between 20 and 25 years of age (OR 1.19; 95% CI 0.99–1.42; p = 0.06) [30]. This evidence concerns the gene BRCA1 and breast cancer.