Abstract PO2-03-03: The Significance of Cavity Shave Margins in Breast Carcinoma on Margin Status and Re-excision Rates

Abstract Context: The comparative outcomes of breast conserving surgery (BCS) with and without cavity shave margins are not well established. We aim to evaluate the impact of each procedure on final margin status and rate of re-excision. Design: A total of 529 breast cancer cases from our institution between 2013-2015 were included. Demographic and clinicopathological data including procedure type, tumor type, grade, margins status, and re-excision rates were collected. H&E slides of positive margins (tumor on ink) were reviewed by two pathologists. Appropriate statistical analysis was performed. Results: Out of 529 breast cancer cases, 125 were Ductal Carcinoma in situ (DCIS), 152 were Invasive Ductal Carcinoma (IDC) and 252 had both pathologies. The median age of patients was 59 years (range: 24-90). Patients who underwent excision with shave margins were 162 (35 DCIS, 56 IDC, 71 both) while excision without shave margins were 367 (90 DCIS, 96 IDC, 181 both). Re-excision rates were significantly lower 1) in patients who underwent BCS with cavity shave margins compared to those without (OR 0.32, p< 0.001) and 2) in patients who did not require lymph node excision compared to those who did (OR 4.26, p< 0.001). Additionally, patients who had DCIS had a higher rate of re-excision than those with invasive cancer only (OR 5.17, P< .001). After adjusting for type of tumor, patients who underwent cavity shaving compared to those who did not, no significant difference was seen in tumor at margins (OR 0.73, p=0.282) or tumor within 2mm (OR 1.14, p=0.512) from margins. However, patients with IDC who underwent cavity shave had a higher proportion of negative tumor at the margins (76.5% vs. 67.0%; p=0.051). We found that patients who had an invasive carcinoma (IC) had a lower risk of having tumor at the margin or within 2 mm from the margin than those with DCIS or DCIS+IC, (p< .05). Conclusions: Our data shows that BCS with cavity shave margins is superior with regards to negative margin and re-excision rates when compared to without cavity shave margins. Citation Format: Fadi Zaiem, Anna Numi, Mira Kheil, Asem AbuJamea, Deepti Jain, Omar Abbas, Lauren Larson, Noor Suleiman, Saleh Al-Juburi, Sanaa Awada, Ragad Almsaddi, Hyejeong Jang, Seongho Kim, Nagla Salem, Lydia Choi, Sudeshna Bandyopadhyay, Sunil Jaiman, Rouba Ali-Fehmi. The Significance of Cavity Shave Margins in Breast Carcinoma on Margin Status and Re-excision Rates [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-03-03.