Trends in Contralateral Prophylactic Mastectomies Before and After the American Society of Breast Surgeons Consensus Statement

Introduction: In 2016, an American Society of Breast Surgeons (ASBrS) statement discouraged contralateral prophylactic mastectomy (CPM) in average-risk women with unilateral breast cancer. Despite evidence of no oncologic benefit and related attempts to discourage the practice, CPM remains prevalent. This study aims to assess CPM trends post-ASBrS statement and factors associated with these trends.

Methods: A retrospective cohort study of patients with primary unilateral breast cancer undergoing complete mastectomy at a single-tertiary center between January 2014 and December 2020 was performed. We assessed the proportion opting for CPM, compared pre- and post-ASBrS statement CPM rates, and examined associated patient and tumor factors. Pearson's Chi-square test, Fisher's exact test, and equal variance t-tests were used to compare subsets who underwent CPM versus those who did not.

Results: Of 605 patients, 161 (27%) underwent CPM during our study period, with the median follow-up time for all patients being 58 mo (IQR: 38 to 81). Among all patients, CPM rates ranged from 30% to 14% before the ASBrS statement and then declined from 36% to 19% after the statement. For average-risk patients (no genetic mutation), these rates ranged from 20.2% to 10.2% from 2014 to 2016 and had a steady decline from 23.2% in 2017 to 13.2% in 2020. Only two cases (1.2%) had incidental contralateral breast cancer. Patients undergoing CPM tended to be younger, more likely to have a breast cancer gene mutation, pursue reconstruction, and elect for nipple- or skin-sparing mastectomy. Recurrence and mortality events did not differ significantly. Genetic testing and pathogenic variant rates were greater among CPM patients.

Conclusions: After an initial time lag, CPM rates appear to be decreasing post-ASBrS statement, with ongoing data needed to confirm this trend. CPM rates among breast cancer gene patients align appropriately with guidelines catering to this higher risk population. Better educational tools and decision aids may impact CPM trends and facilitate shared decision-making.