Margin Width and Local Recurrence in Patients Undergoing Breast Conservation After Neoadjuvant Chemotherapy

Background A margin of "no ink on tumor" has been established for primary breast conservation therapy (BCT), but the appropriate margin following neoadjuvant chemotherapy (NAC) remains controversial. We examined the impact of margin width on ipsilateral breast tumor recurrence (IBTR) in the NAC-BCT population. Methods Consecutive patients receiving NAC-BCT were identified from a prospective database. The associations between clinicopathologic characteristics, margin width, and isolated IBTR were evaluated. Results From 2013 to 2019 we identified 582 patients with 586 tumors who received NAC-BCT. The median age of the cohort was 54 years (IQR 45, 62); 84% of patients had cT1/T2 tumors and 61% were clinically node positive. The majority of tumors were HER2+ (38%) or triple negative (TN) (31%). Pathologic complete response was observed in 29%. Margin width was > 2 mm in 517 tumors (88%) and <= 2 mm in 69 (12%). At a median follow-up of 39 months, 14 patients had IBTR as a first event, with 64% occurring within 24 months of surgery. The 4-year IBTR rate was 2% (95% CI 1-4%), and there was no difference based on margin width (3% <= 2 mm vs 2% > 2 mm; p = not significant). On univariate analysis, clinical and pathologic T stage and receptor subtype, but not margin width, were associated with IBTR (p < 0.05). On multivariable analysis, TN subtype and higher pathologic T stage were associated with isolated IBTR (both p < 0.05). Conclusion Pathologic features and tumor biology, not margin width, were associated with IBTR in NAC-BCT patients.