Margin Assessment in Breast-Conserving Surgery: A Comparative Analysis of Frozen Section and Cavity Shave Techniques.

BACKGROUND: Margin status is a critical determinant of local recurrence after breast-conserving surgery (BCS). Achieving negative margins at the initial operation remains a key goal to optimize oncologic outcomes and minimize the need for additional surgery. Techniques to reduce positive margins include intraoperative frozen section (FS) analysis and cavity shave margins (CSMs). This study aimed to compare re-excision rates and operative times between these approaches. METHODS: A retrospective cohort study analyzed adults undergoing BCS with or without sentinel lymph node biopsy (SLNB) from January 2017 to February 2025. Margin assessment technique, clinicopathologic characteristics, re-excision for margin clearance, and operative time were collected. Cases using both FS and CSM were excluded. RESULTS: Among 2224 BCS cases, 1431 (64.4 %) used FS and 793 (35.7 %) used CSM. During 2017-2022, FS was more commonly used, but CSM utilization surpassed FS in 2023. Re-excision rates were similar between FS and CSM overall (12.8 % vs 12.1 %; p = 0.65) and across invasive histologic subtypes, multifocality, bilateral disease, and receipt of neoadjuvant chemotherapy (all p > 0.05). Stratification by procedure type showed that CSM reduced operative time compared with FS by approximately 18 min for BCS alone (53.5 ± 26.9 vs 71.2 ± 22.4 min; p <0.001) and by approximately 5 min for BCS with SLNB (72.8 ± 30.0 vs 77.8 ± 29.1 min; p = 0.005). CONCLUSIONS: After BCS, FS and CSM achieved comparable re-excision rates across histologic subtypes. The CSM technique was associated with significantly shorter operative times, supporting its use as an efficient margin assessment strategy.