Impact of mastectomy in women with stage IV HER2+ breast cancer.

Abstract

e12515 Background: Women with stage IV HER2+ breast cancer typically have longer overall survival (OS) compared to other breast cancer subsets due to the effectiveness of dual anti HER-2 antibody therapy. The role of mastectomy remains controversial. Methods: We reviewed patients who were diagnosed with stage IV HER2+ breast cancer between 2/2015 and 12/2017 at Cleveland Clinic. Overall survival (OS) was estimated by the Kaplan-Meier method, and compared by the log-rank test. Univariable and multivariable analysis were performed using Cox regression to identify predictors of OS. Results: We identified 47 patients, with a median age of 58 (range: 22 – 87). Twenty-eight (60%) and 14 (30%) patients had ER+ and PR+ disease, respectively. Four patients had brain metastasis at time of stage IV diagnosis. All patients received systemic therapy. 17 (36%) patients underwent mastectomy after diagnosis of stage IV breast cancer,. Of the 30 (64%) patients who did not undergo mastectomy, 24 (80%), 2 (7%), and 4 (13%) were treated with both chemotherapy and HER2-directed therapy, chemotherapy alone, and HER2-directed therapy alone, respectively. Breast radiotherapy was performed on 9 (53%) and 8 (27%) patients in mastectomy and no mastectomy cohorts, respectively. Median follow-up time was 22 months . The two-year OS for mastectomy and no mastectomy cohorts were 94% (95% CI: 83 – 100) and 50% (95% CI: 33 – 76), respectively (p=0.009). On univariable analysis, only mastectomy vs no mastectomy (HR: 0.18, 95% CI: 0.04 – 0.80, p=0.025) predicted OS. On multivariable analysis, mastectomy vs no mastectomy has remained to be statistically significant predictor of OS (HR: 0.08, 95% CI: 0.01 – 0.66, p=0.019), whereas age, chemotherapy, HER2-directed therapy, and breast radiation were not independent predictors of improved OS (p>0.05). Conclusions: In our cohort, mastectomy was an independent predictor of longer OS in women with stage IV HER2+ breast cancer.