Predictors of contralateral prophylactic mastectomy in women with a BRCA1 or BRCA2 mutation: the Hereditary Breast Cancer Clinical Study Group.

PURPOSE To evaluate the rate of prophylactic contralateral mastectomy in an international cohort of women with hereditary breast cancer and to evaluate the predictors of uptake of preventive surgery. PATIENTS AND METHODS Women with a BRCA1 or BRCA2 mutation who had been diagnosed with unilateral breast cancer were followed prospectively for a minimum of 1.5 years. Information was collected on prophylactic surgery, tamoxifen use, and the occurrence of contralateral breast cancer. RESULTS Nine hundred twenty-seven women were included in the study; of these, 253 women (27.3%) underwent a contralateral prophylactic mastectomy after the initial diagnosis of breast cancer. There were large differences in uptake of contralateral prophylactic mastectomy by country, ranging from 0% in Norway to 49.3% in the United States. Among women from North America, those who had a prophylactic contralateral mastectomy were significantly younger at breast cancer diagnosis (mean age, 39 years) than were those without preventive surgery (mean age, 43 years). Women who initially underwent breast-conserving surgery were less likely to undergo contralateral prophylactic mastectomy than were women who underwent a mastectomy (12% v 40%; P < 10(-4)). Women who had elected for a prophylactic bilateral oophorectomy were more likely to have had their contralateral breast removed than those with intact ovaries (33% v 18%; P < 10(-4)). CONCLUSION Age, type of initial breast cancer surgery, and prophylactic oophorectomy are all predictive of prophylactic contralateral mastectomy in women with breast cancer and a BRCA mutation. The acceptance of contralateral preventive mastectomy was much higher in North America than in Europe.