Initial Localization Is Associated With Margin Status but Not Re‐Excision Outcomes in Breast Conservation Surgery: A Single‐Center Cohort Analysis

INTRODUCTION: Positive margins following breast-conserving surgery (BCS) remain a common cause of re-operation. Image-guided localization techniques may reduce margin positivity at index wide local excision (WLE), but their influence on re-operation outcomes is less well defined. Our objective was to evaluate the association between index localization method and margin positivity and to assess re-operation pathology and operative outcomes following positive margins in BCS. METHODS: A retrospective cohort study was conducted at a single breast unit including women undergoing re-operation for positive margins following index WLE between January 2020 and January 2025. Patients were stratified by index localization: none, wire, or radio-frequency identification tag (RFID). Localization groups were pooled for comparison with non-localized cases. Primary outcomes were margin involvement pattern at index surgery and residual tumor at re-excision. Secondary outcomes included re-operation type, operative duration, interval to re-operation, and adjuvant radiotherapy. RESULTS: Among 524 index WLEs, 72 patients (13.7%) underwent re-operation for positive margins. Margin positivity was higher in non-localized cases compared with localized cases (18.6% vs. 10.6%; p = 0.013; OR 0.52, 95% CI 0.31-0.85). Among re-operated patients, margin involvement patterns, re-operation strategy, residual tumor rates (39.5% vs. 55.9%; p = 0.238), operative duration, and time to re-operation were similar between groups. All re-operations were performed as day-case procedures without complications. CONCLUSIONS: Localization at index WLE is associated with lower rates of positive margins, reflecting case selection. However, localization does not significantly influence re-operation pathology or operative outcomes once margin positivity occurs.