When the pattern of the first DFS event was assessed between the BRCA1 and BRCA2 cohorts according to hormone receptor status, the only difference was a higher rate of second non-breast cancer primary malignancies (5.2% vs. 1.4%, P = 0.005) in the BRCA1 cohort with hormone receptor-positive disease, being mostly ovarian cancer (Supplementary Table 4). This evidence concerns the gene BRCA1 and breast cancer.