Inadequate margins of excision when undergoing mastectomy for breast cancer: Which patients are at risk?

Background: We analyzed the margin status and risk factors for inadequate margins among patients who underwent skin-sparing mastectomies (SSM) and traditional total mastectomies (TM). Materials and Methods: Patients undergoing mastectomies from 2003 to 2009 were included. Margins of excision were considered positive if carcinoma was at an inked margin and were considered close if such disease was within 2 mm of an inked margin. Results: A total of 426 patients were identified. The mean age was 60 years and 90% were white. Mean tumor size was 2.6 cm and 44% had multiple ipsilateral carcinomas. Of 426 patients, 177 (42%) underwent SSM with reconstruction and 249 (58%) TM. The rate of positive or close margins on the initial specimen was 29% for SSM vs. 12% for TM (P<0.01), and the rate of reoperation for margins was 7% for SSM vs. 2% for TM (P<0.01). Logistic regression analysis revealed that independent risk factors for initial close or positive margins included SSM (odds ratio 2.36, 95% confidence interval [95% CI] 1.05-5.30), multiple ipsilateral tumors (OR 2.12, 95% CI 1.05-4.24), and upperinner quadrant location (OR 2.58, 95% CI 1.07-6.19). Mean follow-up time was 28 months, and the local recurrence rate was 0.9%. Local recurrence rates were not different for those undergoing SSM (1.1%) vs. TM (0.8%, P = NS). Conclusions: Mastectomy patients undergoing SSM, with multiple ipsilateral tumors, and/or upper-inner quadrant disease are at significantly higher risk for inadequate margins of excision. These patients warrant more vigilant intraoperative attention to margin status to ensure adequate margins at the end of the first operation.