Abstract PS2-05-15: Outcome of De-Escalation of Axillary Surgery in Locally Advanced Breast Cancer Patients

Abstract Background: Evidence is supporting de-escalation of axillary surgery in early breast cancer; however, the role of the same in locally advanced breast cancer (LABC) responding to neo-adjuvant chemotherapy (NACT) is unclear. Objective: To evaluate the outcome of cT2-4N1M0 patients undergoing sentinel lymph node biopsy (SLNB) alone who become ycT0-4N0M0 following NACT. Methods: Digital and medical case records of eligible patients registered at Breast Cancer Clinic were assessed retrospectively for the year 2022-2023 and prospectively for 2024. Clinical presentation, results of cytology, histology, treatment received and follow-up were noted in a predesigned proforma. After SLNB, patients with positive SLN showing macro metastasis or those in whom a sentinel lymph node (SLN) could not be identified were subjected to axillary lymph node dissection (ALND). The primary outcome of the study was composite outcome of mortality, locoregional, or distant recurrence rates, overall survival (OS) and disease-free survival (DFS) in overall population and their comparison between the patients undergoing SLNB alone vs SLNB followed by ALND. Data were analyzed by SPSS version 25. Results: A total of 82 breast cancer LABC patients with ycN0 after NACT were included. All the patients had a dual mapping procedure with either blue dye and indocyanine green [54 (67.5)] or blue dye with Technetium [26 (32.5%)] for SLNB. A sentinel lymph node was identified in 77 (93.9%) cases of which 24 (31.2%) were positive (Table 1). Of 82 cases, a total of 25 (30.4%) patients underwent ALND either because of positive SLN showing macrometastasis (n=20) or non-identification of SLNs (n=5). Median (IQR) lymph nodes removed during SLNB and ALND were 3(2–4) and 13(15–19), respectively. All these patients were followed-up for a median (IQR) duration of 21(15-29) and range (9-44) months. Composite outcome, locoregional recurrence and distant metastasis occurred in 7.0%, 3.5% and 1.8%, respectively in 57 patients undergoing SLNB alone. In the ALND group (n=25), 12.0%, 4.0% and 4.0% patients developed composite outcome, locoregional recurrence and distant metastasis, respectively. These outcomes remained comparable in SLNB and ALND groups. Mean (95%CI) OS was 42.7 (40.3–45.1) months and 37.8 (35.7–39.9) months in SLNB and ALND treated patients, respectively (p=0.617). There was no significant difference in DFS duration between the groups [DFS (months), SLNB vs ALND: 40.4(37.3–42.6) vs 35.3(31.6–39.0), respectively, p=0.414] also. Conclusions: The short-term outcomes suggest low rates of composite, locoregional/ distant recurrences, OS and DFS in LABC patients with ycN0 disease after NACT treated with SLNB followed by regional nodal irradiation supporting axillary nodal de-escalation surgery in this cohort. Citation Format: B. K. Singh, M. Sangade, R. mukherjee, A. Krishna , S. Soren, V. Seenu, A. Batra, S. Mathur. Outcome of De-Escalation of Axillary Surgery in Locally Advanced Breast Cancer Patients [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-05-15.