BRCA1 and breast cancer: For women, the cumulative lifetime risk 20 years after breast cancer diagnosis is 40% (95% CI, 35–45%) for BRCA1 and 26% (95% CI, 20–33%) for BRCA2 carriers (hazard ratio [HR] for comparing BRCA2 vs. BRCA1, 0.62; 95% CI, 0.47–0.82; P = 0.001 for difference) [3], and is reduced in women who take tamoxifen or who undergo oophorectomy.