Abstract PO2-23-01: Selective cavity margin shaving: effective method to maintain balance between cosmesis and negative margin in breast conserving surgery

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Abstract Background: Breast conserving surgery (BCS), which became the mainstay of breast cancer surgery, both cosmesis and margin negativity are significant issues. Firstly, it is well known that negative resection margin is crucial for reducing local recurrence after BCS. Therefore, there has been numerous attempts to secure negative margin, such as specimen mammography, frozen section margin analysis, and cavity margin shaving. Regarding cosmesis, wider excision to secure negative margin could disrupt cosmesis especially in Asian patients with relatively smaller breast, and minimizing excision volume is necessary for optimal cosmetic outcome. Our center adopted the concept of selective cavity margin shaving (SCMS) to achieve negative margin while optimizing cosmetic result. Method: 606 female patients with non-metastatic, unilateral breast cancer were prospectively collected and underwent BCS with SCMS from October, 2012 to December, 2020. The medical record was retrospectively reviewed, and we assessed positive margin rate and local recurrence. During BCS, the surgeon excised gross margin of 1~2cm around the cancer, and assessed the proximity of the margin through gross examination. If sufficient margin was not obtained, cavity shaving was performed in the close margin, while shaving from retrieved specimen was conducted on the sufficient margin side. Additionally, circumferential margin frozen analysis was carried out, and further excision was performed until a negative margin was achieved or when only focal DCIS involvement remained. Result: The mean ± SD age of the patients was 52.47 ± 9.92 years and mean follow-up period was 59.98 ± 26.59 months. 56 patients (9.24%) received neoadjuvant chemotherapy. 123 patients (20.29%) got positive margin for invasive cancer or DCIS in frozen section margin analysis and 97 patients (16.01%) underwent intraoperative re-excision. There was discordance between frozen and permanent section margin analysis in 48 patients (7.92%), and 7 patients (1.16%) underwent post-operative re-excision operation. Local recurrence occurred in 11 patients (1.82%), which is significantly lower compared to previously reported outcomes after BCS. Presence of lympho-vascular invasion, neoadjuvant chemotherapy, and margin involvement of invasive cancer in permanent section analysis were strongly related with local recurrence. Conclusion: In conclusion, SCMS and frozen section margin analysis demonstrated low positive margin rate and reduced re-excision rate. The local recurrence was also lower compared to conventionally reported rate after BCS. Selective cavity margin shaving is an oncologically safer and effective surgical method with minimized cosmetic deformity. Table 1. Baseline patient characteristics Table2. Univariate and multivariate analysis of factors associated with local recurrence Table2. Univariate and multivariate analysis of factors associated with local recurrence by Cox proportional hazard model. Citation Format: Dabin Kim, Zisun Kim, Sung Mo Hur, Cheol wan Lim. Selective cavity margin shaving: effective method to maintain balance between cosmesis and negative margin in breast conserving surgery [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 PO2-23-01.