New research presented at the seventh European Breast Cancer Conference (EBCC7) in Spain has reported that contralateral mastectomy in BRCA1/2 mutation carriers who develop breast cancer in one breast does not improve survival. Risk-reducing mastectomy in BRCA1/2 mutation carriers with a history of unilateral breast cancer is known to significant reduce the risk of developing contralateral breast cancer (cancer in the other breast). However, the outcome regarding distant metastasis-free survival and overall survival has not been established.

The study included 375 breast cancer patients (283 with BRCA1 mutations and 92 with BRCA2). Cancer characteristics and follow-up information through year-end 2008 were obtained from medical records. Eventually, 111 of the BRCA1 and 33 of the BRCA2 mutation carriers underwent risk-reducing mastectomy. No differences in age at diagnosis, hormone-receptor status, and adjuvant systemic treatment were found between the non-risk-reducing mastectomy and risk-reducing mastectomy groups with respect to the initial (primary) beast cancer. Distribution of TNM stages 0, I, II and III, was 4%, 37%, 46% and 13%, respectively, in the non-risk-reducing mastectomy group, compared to 4%, 51%, 38% and 7% in the risk-reducing mastectomy group. More women in the risk-reducing mastectomy group also underwent risk-reducing removal of the fallopian tubes and ovaries (74% compared to 46% in the non-risk-reducing mastectomy group).

With an average follow-up of 7.4 years, 72 contralateral breast cancer cases occurred in the non-risk-reducing mastectomy group, whereas no contralateral breast cancer occurred after risk-reducing mastectomy. Fifty-four patients in the non-risk-reducing mastectomy group developed metastatic cancer versus 16 patients in the risk-reducing mastectomy group. Concerning the overall survival, 51 women died in the non-risk-reducing mastectomy group, compared to 15 women in the risk-reducing mastectomy group. BRCA1 and BRCA2 mutation carriers were found to have similar results. The effect of risk-reducing mastectomy on distant disease free survival and overall survival taking into account the influence of variables such as tumor characteristics, mutation status, and risk-reducing salpingo-oophorectomy is currently being analyzed and is not yet available. The authors conclude that risk-reducing mastectomy in BRCA1/2 mutation carriers with a history of unilateral breast cancer does not appear to improve distant disease free survival and overall survival, despite resulting in a dramatic reduction in contralateral breast cancer occurence. They comment that further research is warranted to identify a set of prognostic factors enabling selection of subgroups of breast cancer patients who possibly may benefit from risk-reducing mastectomy with respect to distant disease free survival and overall survival.