The Shifting Paradigm for Breast Cancer Surgery in Patients Undergoing Neoadjuvant Chemotherapy.

INTRODUCTION: Surgical therapy for newly diagnosed breast cancer has changed over the past decade, but these trends have not been well documented in patients undergoing neoadjuvant therapy (NAC).

METHODS: In a retrospective cohort study of the National Cancer Database (NCDB), we selected 285,514 women with clinical stage I-III breast cancer who underwent NAC or adjuvant therapy (AC) from 2006 to 2014. Breast-conserving surgery (BCS), unilateral mastectomy (UM), and bilateral mastectomy (BM) rates were compared between patients undergoing NAC and AC.

RESULTS: Of 285,514 women, 68,850 (24.1%) underwent NAC. Of NAC patients, 18,158 (26.4%) underwent BM and 27,349 (39.7%) BCS compared with 31,886 (14.7%) and 120,626 (55.7%) AC patients, respectively. From 2006 to 2014, BM increased from 16.1 to 28.8% (p < 0.001) for NAC and from 7.4 to 17.5% (p < 0.001) for AC. After adjusting for patient, tumor, and facility factors, NAC patients were 1.50 times [odds ratio (OR) 1.50, confidence interval (CI) 1.42-1.51] more likely to undergo BM then AC patients. The difference in BM rates between patients receiving NAC versus AC varied significantly by cT classification. This difference was the greatest among cT1 tumors between NAC and AC (31.7 vs. 13.0%, p < 0.001), followed by cT2 tumors (24.1 vs. 16.6%, p < 0.001) and cT3 tumors (24.3 vs. 22.3%).

CONCLUSIONS AND RELEVANCE: More NAC patients are undergoing BM while fewer are undergoing BCS compared with patients undergoing AC. This trend is particularly striking for those patients with smaller tumors who would otherwise be candidates for BCS.