Incidence and outcomes of contralateral breast cancers

Background The significance of a contralateral breast cancer is largely unknown, making prophylactic mastectomy controversial. Methods Differences between stages of initial and contralateral cancers were determined by t test. Survival distributions were compared by log-rank analyses and compared with Surveillance Epidemiology and End Results data for unilateral cancers. Results Metachronous contralateral cancers occurred at a rate of .13% per year and were of significantly lower stage. Metachronous cancers adversely impacted survival for patients with low-stage initial cancers, but the interval between cancers was less than 36 months. Synchronous tumors occurred in 2.3% of patients; survival was worse than for patients with metachronous cancers. Conclusions Prophylactic mastectomy is unlikely to be beneficial because of the lower stages and low incidence of second cancers, even for patients with initial low-stage cancers.