Abstract P1-16-03: Residual disease after breast conservation surgery: To excise or not to excise?

Abstract

Abstract Background: The definition of adequate margins after breast conservation surgery for invasive breast cancer has been a highly debated topic. A recent consensus statement by the SSO/ASTRO recommends re-excision only for positive margins, defined as tumor at ink. In light of this consensus statement, we studied the characteristics of patients undergoing breast conservation surgery with subsequent re-excision at our institution in order to examine factors predictive for residual disease (RD+) in the re-excision specimen, as well as a second re-excision. Methods: In this IRB approved retrospective chart review of our breast cancer cases from 1998-2013, we reviewed 828 patients who underwent breast conservation surgery with re-excision for invasive breast carcinoma. A close margin was defined as less than 2mm from the inked margins, and a positive margin was defined as tumor at ink. We analyzed various clinicopathologic features. RD+ was missing in 7 patients (0.8%), who were excluded from that analysis. Pearson chi-square was used to test significance in univariate analysis. Binary logistic regression was applied in multivariate analysis of factors significant at p<0.05. Results: Overall, 230 patients (28%) had RD+, and 103 patients required a second re-excision (12.4%) due to persistently positive or close margins (44% of RD+). Factors not significant for RD+ were: diagnosis era (before June 2007 vs. after), menstrual status, age < 40, race, excision volume, tumor size, nodal status, grade, histology, lymphovascular invasion, and hormone receptor status. For patients with only close margins, there was no difference in RD+ by margin width, as defined by <0.5mm, 0.5 to <1mm, 1mm to <2mm. Factors significant for RD+ were: disease that was mammographically occult or calcifications only (35%) vs. mass or architectural distortion (25%), p=0.003; positive margin vs. close margin (33% vs. 24%, p=0.004); margin positive or close for DCIS (41%) vs. both DCIS/invasive (30%) vs. invasive alone (17%), p<0.001; presence of DCIS (30% vs. 16%, p=0.001); extensive intraductal component (EIC) (42% vs. 24%, p<0.001); the number of positive or close margins (1: 16%, 2: 26%, 3+: 48%, p<0.001). In multivariate analysis, the number of positive or close margins was significant, (p<0.001), as was a margin positive or close for DCIS (p<0.001). Factors significant in univariate analysis for a second re-excision were similar as those for RD+. In multivariate analysis, independent factors for second re-excision were: EIC (p=0.007), number of positive or close margins (p<0.001), and a margin positive or close for DCIS (p=0.001). Conclusions: Residual disease at re-excision for positive or close margins was present in approximately one-fourth of patients. The probability of residual disease was unrelated to margin positivity or margin width within 2mm. Consideration of re-excision should take into account the burden of intraductal disease in the specimen, its presence at or close to the margin, and the number of positive or close margins. Citation Format: Catherine R Campo, Erika Reategui, Sarah P Cate, John Rescigno, Priyanka Mittar, Alyssa Gillego, Susan K Boolbol. Residual disease after breast conservation surgery: To excise or not to excise? [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-16-03.