BRCA1 and breast cancer: For BRCA1 heterozygotes, the (ER)-negative PRS313 showed the strongest association with contralateral breast cancer risk (HR = 1.12, 95% CI [1.06–1.18]), while for BRCA2 heterozygotes, the ER-positive PRS313 was more strongly associated with contralateral breast cancer risk (HR = 1.15, 95% CI [1.07–1.25]) [64].