The Impact of Neoadjuvant Chemotherapy on Margin Re-excision in Breast-Conserving Surgery

BACKGROUND: Neoadjuvant chemotherapy (NAC) can improve cosmesis by reducing resection volume. Breast-conserving surgery (BCS) aims to achieve clear excision margins while optimizing cosmesis. However, the influence of NAC on margin re-excision after BCS is unclear. This study examines the rate and determinants of margin re-excision in patients undergoing BCS following NAC in our institution. METHODS: From 2011-2015, all patients treated with NAC prior to BCS were identified from a prospectively maintained database. Mann-Whitney and Fisher's exact test tests were used to compare variables in patients who did and did not require re-excision. Patients undergoing primary surgical treatment in 2015 comprised an unmatched comparison group. RESULTS: Of 211 patients treated with NAC, 69 initially underwent BCS. The re-excision rate was 32% (n = 22) compared to 17% in the primary operable group (38 of 221, p = 0.02). Re-excision rates were lowest in triple-negative and HER2+ tumors (0% and 10%, respectively). Lobular carcinoma and ER+ tumors had a significantly higher rate of re-excision (100% and 42%, respectively). Of 22 patients undergoing re-excision, 9 had further BCS and 13 had a mastectomy. CONCLUSION: The re-excision rate following NAC is almost twice that of patients who underwent primary operative management. Her2+ and triple-negative tumors have lower re-excision rates and may represent a selected cohort most suitable for BCS. Patients with invasive lobular carcinoma or ER+ disease have significantly higher rates of margin positivity, and these patients should be considered for a cavity shave during primary surgery to reduce the rates of re-excision.