For rs1045494 in CASP8, rs4687554 in MUSTN1 and rs3134615 in MYCL1 (OR 1.03 [95%CI 1.01–1.05]; P = 7.75×10−4) a more significant association with breast cancer risk was found for the ER positive subgroup than in the main analysis, but the result from the test for heterogeneity by ER status was not significant (data not shown). This evidence concerns the gene ESR1 and breast cancer.