Similarly, the median number of mutations in TCGA BRCA1- and BRCA2-deficient breast cancers being 2.2 and 2.0 fold higher, respectively, compared to BRCA-proficient breast cancers (P = 6.6 x 10−9 and 6.0 x 10−6, respectively; Fig 1D). This evidence concerns the gene BRCA1 and breast cancer.