Objective: To identify factors predicting positive margins at lumpectomy prompting intraoperative reexcision in patients with breast cancer treated at a large referral center. Patients and Methods: We reviewed all breast cancer lumpectomy cases managed at our institution from January 1, 2012, through December 31, 2013. Associations between rates of positive margin and patient and tumor factors were assessed using χ2 tests and univariate and adjusted multivariate logistic regression, stratified by ductal carcinoma in situ (DCIS) or invasive cancer. Results: We identified 382 patients who underwent lumpectomy for definitive surgical resection of breast cancer, 102 for DCIS and 280 for invasive cancer. Overall, 234 patients (61.3%) required intraoperative reexcision for positive margins. The reexcision rate was higher in patients with DCIS than in those with invasive disease (78.4% [80 of 102] vs 56.4% [158 of 280]; univariate odds ratio, 2.80; 95% CI, 1.66-4.76; P<.001). Positive margin rates did not vary by patient age, surgeon, estrogen receptor, progesterone receptor, or ERBB2 status of the tumor. Among the 280 cases of invasive breast cancer, the only factor independently associated with lower odds of margin positivity was seed localization vs no localization (P=.03). Conclusion: Ductal carcinoma in situ was associated with a higher rate of positive margins at lumpectomy than invasive breast cancer on univariate analysis. Within invasive disease, seed localization was associated with lower rates of margin positivity.
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