BRCA1 and breast cancer: In breast cancer, there are three breast cancer cluster regions in BRCA1: c.179 to c.505 (RHR = 1.46; 95% CI, 1.22–1.74; P = 2 × 10− 6), c.4328 to c.4945 (RHR = 1.34; 95% CI, 1.01–1.78; P = .04), and c.5261 to c.5563 (RHR = 1.38; 95% CI, 1.22–1.55; P = 6 × 10− 9).