The aim of this study was to investigate whether contralateral prophylactic mastectomy (CPM) in addition to therapeutic mastectomy (TM) is associated with a survival advantage in high-risk women with breast cancer.

A total of 385 women with stage I or II breast cancer and a family history of breast cancer who underwent TM and CPM between 1971 and 1993 were evaluated and compared to 385 patients matched on age at diagnosis, tumor stage, nodal status, and year of diagnosis who underwent TM-only. Contralateral breast cancer (CBC) events and survival outcomes were compared.

At a median follow-up of 17.3 years, 2 CBCs (0.5%) developed in the CPM cohort and 31 (8.1%) in the TM-only cohort, representing a 95% decreased risk of CBC (hazard ratio [HR] = 0.05, 95% confidence interval [95% CI] 0.01-0.22, P < 0.0001). One hundred twenty-eight women in the CPM group and 162 women in the TM-only group have died, resulting in 10-year overall survival estimates of 83 and 74%, respectively (HR 0.68, 95% CI 0.54-0.86, P = 0.001). This difference in overall survival persisted in multivariate analysis (HR 0.77, P = 0.03). Disease-free survival (DFS) was better in the CPM cohort than the TM-only group (HR 0.66, 95% CI 0.53-0.82, P = 0.0002) and remained significant in multivariate analysis (HR 0.67, P = 0.0005).

In this retrospective cohort study, CPM was associated with decreased CBC event and improved overall survival and disease free survival.