Of the 27 previously established breast cancer–associated loci, all but 4 showed clear evidence of association with overall breast cancer risk in the iCOGS stage (P = 2.2 × 10−5 – P = 5.9 × 10−125; Supplementary Table 4). Three loci showed weaker evidence for association: rs1045485, encoding an Asp302His variant in CASP8, whose association was previously identified in a candidate gene study (P = 0.054 in the iCOGS stage; P = 0.0013 in combined data from the GWAS and iCOGS stages)21; rs2380205 at 10p15, identified in a GWAS but suggested to be a possible false positive association in a previous BCAC analysis22,23 (iCOGS P = 0.075; combined P = 0.0021); and rs8170 at 19p13.1, for which the association has been shown to be specific to estrogen receptor (ER)-negative breast cancer24 (P = 0.0027 in iCOGS; combined P = 0.0012). One locus, rs2284378 at 20q11, recently shown to be associated with ER-negative breast cancer, was not selected for the iCOGS array16.
