BRCA1 and breast cancer: Prophylactic risk-reducing bilateral salpingo-oophorectomy (RRBSO) reduces ovarian cancer risk in women with BRCA mutations by 72%-88%.153 RRBSO also reduces breast cancer risk by about 50%.154 Use of MHT to treat symptoms of surgically-induced menopause after RRBSO may increase breast cancer risk in BRCA1 or BRCA2 mutation carriers, especially BRCA2 carriers who are more likely to develop ER positive disease, but MHT does not seem to significantly alter the reduction in breast cancer risk associated with RRBSO in observational studies.155