BRCA1 and cancer: BRCA1, BRCA2, BRIP1, ATR, and ATM have all a mutation frequency of 6% or higher (up to 9% for BRIP1 and ATM) in PIK3CA mutated cancers, although the overall mutation rate in the DNA damage response genes did not reach statistical significance between the PIK3CA mutant and PIK3CA wild-type groups (Fisher’s exact test p = 0.15, Figure 6).