Axillary Surgery in Breast Cancer: Evidence-Based De-escalation Across Upfront and Post-Neoadjuvant Settings

Axillary surgery in breast cancer has progressively shifted from radical clearance to selective de-escalation. Sentinel lymph node biopsy (SLNB) replaced axillary lymph node dissection (ALND) as the standard, markedly reducing morbidity while maintaining oncologic safety. More recently, randomized trials have challenged even the necessity of SLNB in certain patients, reflecting a broader movement toward optimization rather than maximal intervention. Evidence can be grouped according to the burden of sentinel node metastasis. Micrometastasis-focused trials (IBCSG 23-01, AATRM) showed that omission of ALND in patients with one or more micrometastases (≤ 2 mm) did not compromise survival or locoregional control. Mixed-burden trials (ACOSOG Z0011, AMAROS) included patients with 1-2 positive sentinel lymph nodes, regardless of micrometastatic or macrometastatic size, and confirmed the safety of avoiding ALND when appropriate systemic therapy and radiotherapy are given. Macrometastasis trials (SENOMAC, SINODAR-ONE, POSNOC) extended these findings to patients with 1-2 macrometastases (≥ 2 mm), demonstrating that ALND omission is still safe even in higher-burden disease. In parallel, de-escalation has advanced further. SOUND and INSEMA established non-inferiority of observation vs. SLNB in clinically node-negative (cN0), imaging-negative tumors, while ongoing studies such as NAUTILUS are validating these results in Asian populations. In the neoadjuvant setting, SLNB is standard for cN0 patients and feasible in clinically node-positive patients who convert to cN0 after neoadjuvant chemotherapy. Ongoing trials (ASICS, EUBREAST-01, ASLAN) are exploring whether axillary surgery can be omitted entirely in excellent responders, particularly in human epidermal growth factor receptor 2-positive and triple-negative breast cancer. The collective data indicate a clear trend. Axillary surgery should be optimized to disease biology, systemic therapy response, and patient quality of life.