Sentinel lymph node biopsy without frozen section in mastectomy patients: A 5-year survival analysis from King Chulalongkorn Memorial Hospital

Background Intraoperative frozen section (FS) during sentinel lymph node biopsy (SLNB) has traditionally been used to facilitate immediate axillary lymph node dissection (ALND). However, contemporary axillary de-escalation strategies supported by AMAROS and SENOMAC trials have narrowed indications for ALND, raising questions about the clinical value of routine FS, particularly in mastectomy patients. Methods We retrospectively analyzed early-stage breast cancer patients (T1–T2, clinically node-negative) who underwent mastectomy with SLNB at a single institution between 2017 and 2022. Patients were managed with either intraoperative FS or permanent section (PS) alone. The primary endpoint was 5-year disease-free survival (DFS) using a noninferiority design. Secondary endpoints included overall survival (OS) and patterns of recurrence. Results Among 265 patients, 202 underwent SLNB with FS and 63 with PS alone. Median follow-up was 5.7 and 4.8 years, respectively. Five-year DFS was 92.1% in the FS group and 93.7% in the PS group. The PS strategy was noninferior to FS (hazard ratio [HR], 0.96; 95% CI, 0.28–3.35; noninferiority P = 0.952). Overall survival was comparable (HR, 1.09; 95% CI, 0.13–9.17). Rates of local, regional, and distant recurrence did not differ significantly. Only one patient in the PS group required delayed ALND. Conclusions Omission of intraoperative FS during SLNB in mastectomy patients did not compromise long-term oncologic outcomes. A PS-only strategy appears safe and supports further axillary de-escalation in contemporary practice.