Background: Risk factors for contralateral breast cancer (CBC) may indicate a benefit for contralateral prophylactic mastectomy (CPM) at the time of unilateral mastectomy for breast cancer. The purpose of this study is to evaluate the efficacy of CPM in preventing CBC.
Methods: sixty-four patients undergoing CPM and a control group of 182 patients not undergoing CPM and matched for age, stage, surgery, chemotherapy, and hormonal therapy were retrospectively compared for CBC rate, disease-free survival, and overall survival.
Results: Thirty-six CBCs occurred in the control group. In the CPM group, 3 CBCs were found at the time of prophylactic mastectomy, but none occurred subsequently (P = 0.005). Disease-free survival at 15 years in the CPM group was 55% (95% confidence interval [CI] 38% to 69%) versus 28% (95% CI 19% to 36%) in the control group (P = 0.01). Overall survival at 15 years was 64% (95% CI 45% to 78%) CPM versus 48% (95% CI 39% to 58%) in controls (P = 0.26).
Conclusion: CPM prevented CBC and significantly prolonged disease-free survival. Future studies will need to address risk assessment and contralateral breast cancer prevention in patients treated for early breast cancer.