BRCA1 and breast cancer: By contrast, prostate cancer is the most common cancer in men, accounting for approximately 25% of male tumors.6 The lifetime risk of male breast cancer in mutation carriers has been estimated to be 5% to 10% and 1% to 5% for carriers of BRCA2 and BRCA1 mutations, respectively, whereas estimates of lifetime prostate cancer risk are approximately 20% and 40% for carriers of BRCA1 and BRCA2 mutations, respectively.3,7-10