BRCA1 and breast cancer: For instance, the incidence of second breast cancer in ovarian cancer patients with BRAC1/2 mutation was reported to be 8.9% 16, and the risk of second uterine cancer is also significant in BRCA1 carriers (SIR = 1.91, P = 0.03), but not in BRCA2 carriers (SIR = 1.75, P = 0.20) 6.