Effects of Breast-Conserving Surgery and Mastectomy on the Survival of Patients with Early-Stage (T1-2N0-1M0) HER2-Positive Breast Cancer: A Propensity Score-Matched Analysis.

INTRODUCTION: Although breast-conserving therapy (BCT) promises at least a similar survival rate for patients with early breast cancer compared with mastectomy, its efficacy in patients with human epidermal growth factor receptor 2 (HER2)-positive tumors remains unclear. Therefore, we conducted this study to explore differential effects of BCT and mastectomy on survival outcomes of patients with early-stage HER2-positive breast cancer.

METHODS: Data were extracted from the Surveillance, Epidemiology, and End Results (SEER) database, and basic characteristics of patients who received either BCT or mastectomy were balanced using propensity score matching (PSM). Kaplan-Meier analysis, log-rank testing, and Cox proportional hazards regression were performed.

RESULTS: In total, 20,277 patients were diagnosed with T1-2N0-1M0 HER2-positive breast cancer between 2010 and 2015. After PSM, 6,185 pairs of patients were enrolled for further analysis. Compared with those undergoing mastectomy, patients receiving BCT had superior overall survival (OS) (hazard ratio [HR], 0.63; 95% confidence interval [CI]: 0.55-0.73; p < 0.001) and breast cancer-specific survival (BCSS) (HR: 0.59; 95% CI: 0.48-0.71; p < 0.001). The subgroup analyses revealed that survival outcomes (OS and BCSS) of BCT were better than those of mastectomy among estrogen receptor (ER)+/progesterone receptor (PR)+/HER2+, ER+/PR-/HER2+, and ER-/PR-/HER2+ subtypes (p < 0.05 for all); however, patients with ER-/PR+/HER2+ subtypes who underwent BCT had similar OS and BCSS (p > 0.05 for both) to those treated with mastectomy.

DISCUSSION/CONCLUSION: Despite the aggressiveness of the disease, we found that BCT may confer better long-term survival than mastectomy for patients with T1-2N0-1M0 HER2-positive breast cancer, particularly for those with ER+/PR+/HER2+, ER+/PR-/HER2+, and ER-/PR-/HER2+ subtypes. In addition, our study provided insights into the clinical applications of BCT. However, this retrospective study has introduced several inevitable limitations, and further prospective research is warranted to verify these conclusions.