Accordingly, statistical analyses of the most altered genes in our dataset showed that LoF of XRCC3 is mutually exclusive with either BRCA1 (Fisher exact P value 0.002) or BRCA2 (Fisher exact P value 0.01) LoF when considering the pan-cancer dataset (Supplementary Fig. S4A and S4B), an effect that becomes even more significant when limiting the analysis to ovarian, breast, pancreatic, and prostate tumors (BRCA1 P value 4.1E-07; BRCA2 P value 6.4E-04; Fig. 4A). Here, BRCA1 is linked to cancer.