Introduction: A 2014 consensus statement from the Society of Surgical Oncology and American Society for Radiation Oncology supported “no ink on tumor” as an adequate margin for breast conserving therapy (BCT). This study evaluates this statement in a multi-institution cohort. Methods: A retrospective review of BCT cases at 3 comprehensive cancer centers was performed. Women age >18 receiving BCT for T1-2 breast cancer from 2008-2012 were included. Pre-2014, all sites considered 2 mm adequate. Estimated re-excision rates using the 2014 guidelines were calculated and factors predictive of re-excision were analyzed. Results: 542 patients (545 lumpectomies) were eligible. Using a ≥2 mm margin standard, 32.8% of patients underwent re-excision compared to 14.1% after 2014 (p < 0.0001). Tumor size (p= 0.003), grade (p=0.015), and lymphovascular invasion (p=0.021) were predictive of re-excision. Patients with additional intraoperative margins excised were less likely to require reoperation (p=0.002). Local recurrence was unaffected by re-excision after mean followup of 66 months. Conclusions: The 2014 margin guidelines markedly reduce re-excision rates. There is no difference in local recurrence for patients after re-excision for a close margin versus without Powered.
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