BRCA1 and breast cancer: Using the retrospective likelihood approach, index SNPs in the three 2p23.2 and 13q22 loci were all associated with BRCA1 breast cancer (rs67073037, P=4.58 × 10−4; rs6562760, P=2.85 × 10−6; rs17181761, P=9.29 × 10−3; Table 2).