LAUSR

Background: Negative margins are important in decreasing risk of local recurrence after breast conservation surgery. Further, positive margins on final pathology require a second operation, burdening patients and increasing costs. We identified factors predicting positive margins at lumpectomy prompting intraoperative re-excision in a large referral center. Methods With IRB approval we reviewed all breast cancer lumpectomy cases from January 2012 to December 2013. Associations between rates of positive margin (defined as tumor at ink) and patient and tumor factors were assessed using chi square tests and univariate and adjusted multivariable logistic regression, overall and stratified by DCIS or invasive cancer. Results 385 patients (105 DCIS and 280 invasive disease) were identified. Overall positive margin rate at lumpectomy requiring intraoperative re-excision was 62.3% and was higher in DCIS than in invasive disease (78.1% vs 56.4%, OR=2.78, p=0.001). Positive margin rates did not vary by surgeon, patient age, ER, PR or HER2 status of the tumor. On univariate analysis higher tumor grade was associated with a higher margin positive rate (grade 3 vs grade 1, OR=1.71, p=0.049). Within the 105 DCIS cases, no factors had statistically significantly different odds of positive margins on univariate or multivariable analysis. Within the 280 cases of invasive breast cancer, factors independently associated with lower odds of margin positivity were neoadjuvant chemotherapy (OR 0.30, p=0.037, relative to no neoadjuvant therapy) and seed localized excision (OR 0.24, p=0.03, relative to no localization). Conclusion DCIS was associated with higher rate of positive margins at lumpectomy than invasive breast cancer. Within invasive disease, neoadjuvant chemotherapy and seed localization were associated with lower rates of margin positivity. Strategies to decrease positive margins would be best employed in cases of lumpectomy for DCIS and for invasive disease treated without neoadjuvant chemotherapy. Seed localization may be one strategy to lower positive margin rates. Citation Format: Boughey JC, Keeney MG, Glasgow AE, Keeney GL, Habermann EB. Tumor and procedural factors associated with positive margins at lumpectomy in women undergoing breast conservation surgery [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-11-08.