Abstract P4-13-06: Does large volume displacement oncoplastic surgery still offer an advantage of a low positive margin rate using the new SSO/ASBrS/ASTRO margin guidelines?

Purpose Breast conservation has become the mainstay of surgical management for early stage breast cancer. Large volume displacement oncoplastic surgery (LVOS) uses reconstructive mastopexy and breast reduction techniques to allow for larger oncologic resections while providing good aesthetic outcomes in a single operation. Oncoplastic surgery publications have recently increased by 220%, demonstrating the increasing popularity of this surgical technique, 2 and many of these studies have demonstrated excellent oncologic outcomes. 4 To date, however, no study has used the most recent SSO/ASBrS/ASTRO surgical margin recommendations to assess oncoplastic surgery. 4 Recent SSO/ASBrS/ASTRO guidelines established no ink on tumor as an adequate margin for invasive breast cancer and at least 2mm as adequate margins for ductal carcinoma in situ. The purpose of this study was to investigate the surgical margin rates of LVOS using the new SSO/ASBrS/ASTRO guidelines. We presumed that under the newer, stricter guidelines, LVOS would have a higher positive margin rate than reported in the past literature. Methods: Our study consisted of two parts. First, a literature review to assess margin rates before the introduction of SSO/ASBrS/ASTRO guidelines was done using PRISMA guidelines with an international Pubmed search and reviewed by two blinded authors. The search included keywords such as “oncoplastic breast surgery,” “lumpectomy,” “partial mastectomy,” and “positive margins associated with breast surgery.” All articles either pertained to LVOS, standard lumpectomy (SL) or both. The inclusion criteria for our study included histology discrepancy, and new guideline margin status. From this, we determined the published positive margin for SL and LVOS. Second, we analyzed all LVOS performed at our institution since the adoption of the new SSO/ASBrS/ASTRO margin guidelines and compared these margin rates to the literature review outcomes using Z tests. Results: Our study consisted of 1702 patients. There were 847 patients in LVOS group and 855 patients in the SL group. Of the 45 papers evaluated, 34 were not included due to exclusion criteria (missing: new margin guidelines, histology, or margin status). The pre-guideline positive margin rate for LVOS was lower than with SL (12.51% vs. 20.4%, P-value Conclusions: This study demonstrates that even with the stricter margin SSO/ASBrS/ASTRO guidelines, LVOS still has a low positive margin rate comparable to pre-guideline literature reports. LVOS continues to have a significantly lower positive margin rate than SL. This is the first study to report margin rates for LVOS after the adoption of the SSO/ASBrS/ASTRO guidelines, and confirms the importance of LVOS in providing optimal oncologic outcomes for patient with large locally advanced breast cancer. Citation Format: Jonczyk MM, Patel K, Graham R, Naber S, Erban J, Chen L, Chatterjee A. Does large volume displacement oncoplastic surgery still offer an advantage of a low positive margin rate using the new SSO/ASBrS/ASTRO margin guidelines? [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-13-06.