Background: Reoperation rates following breast-conserving surgery (BCS) range from 10 to 40%, with marked surgeon and institutional variation. Objective: The aim of this study was to identify factors associated with intraoperative margin re-excision, evaluate for any differences in local recurrence based on margin re-excision and determine reoperation rates with use of intraoperative margin analysis. Patients and Methods: We analyzed consecutive patients with ductal carcinoma in situ (DCIS) or invasive breast cancer who underwent BCS at our institution between 1 January 2005 and 31 December 2016. Routine intraoperative frozen section margin analysis was performed and positive or close margins were re-excised intraoperatively. Univariate analysis was used to compare margin status and the Kaplan–Meier method was used to compare recurrence. Multivariable logistic regression was utilized to analyze factors associated with re-excision. Results: We identified 3201 patients who underwent BCS—688 for DCIS and 2513 for invasive carcinoma. Overall, 1513 (60.2%) patients with invasive cancer and 434 (63.1%) patients with DCIS had close or positive margins that underwent intraoperative re-excision. Margin re-excision was associated with larger tumor size in both groups. The permanent pathology positive margin rate among all patients was 1.2%, and the 30-day reoperation rate for positive margins was 1.1%. Five-year local recurrence rates were 0.6% and 1.2% for patients with DCIS and invasive cancer, respectively. There was no difference in recurrence between patients with and without intraoperative margin re-excision (p = 0.92). Conclusion: Both DCIS and invasive carcinoma had similar rates of intraoperative margin re-excision. Although intraoperative margin re-excision was common, the reoperation rate was extremely low and there was no difference in recurrence between those with or without intraoperative re-excision.
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