The impact of contralateral mastectomy on mortality in BRCA1 and BRCA2 mutation carriers with breast cancer.

Among women with breast cancer and a BRCA1 or BRCA2 mutation, the lifetime risk of breast cancer may be as high as 40%. Many physicians recommend prophylactic contralateral mastectomy, which is an effective measure of minimising the risk of contralateral cancer. The benefits of preventive contralateral mastectomy are apparent within 10 years, in terms of preventing cancer, but a much longer time period is required in order to demonstrate a reduction in mortality. Under the simple model presented here, among women who retain the contralateral breast, 0.4% of women are expected to die of contralateral breast cancer within 5 years, but 6.8% are expected to die at 20 years from diagnosis. These unnecessary deaths can be prevented by bilateral mastectomy.