De-escalating the Axilla: A Systematic Evaluation of Sentinel Lymph Node Biopsy Reliability and Oncological Safety in the Post-Neoadjuvant Landscape

Abstract

Introduction: Breast cancer management is increasingly shifting toward minimally invasive procedures. While neoadjuvant chemotherapy (NACT) is used to downstage locally advanced disease, it can induce lymphatic fibrosis, potentially compromising the identification rate (IR) and false-negative rate (FNR) of sentinel lymph node biopsy (SLNB). This systematic review evaluates the reliability and oncological safety of SLNB in patients following NACT. Methodology: Following PRISMA guidelines, a systematic search was conducted across PubMed, Scopus, and Google Scholar using keywords like "Locally Advanced Breast Cancer", “Neoadjuvant Chemotherapy” and "Sentinel Lymph Node Biopsy". Inclusion criteria focused on free full-text studies published between 2020 and 2025 that examined SLNB post-NACT. Ten studies were selected for final analysis, comprising six prospective and four retrospective cohorts. Total number of patients included were 1656. Results: IRs ranged from 49.54% to 96.8%, though dual tracer mapping achieved success rates up to 100%. FNRs varied significantly, from 11% with dual mapping to as high as 50% with single tracers. Accuracy improved notably by harvesting three or more nodes, which reduced the FNR to acceptable levels, reaching 0% in specific cohorts. Innovative methods like the "black node" technique (pre-NACT tattooing) showed an FNR of 0% in initially cN0 patients. Triple-negative and HER2-positive subtypes had the highest response rates, with some achieving zero SLNB-positivity. Five-year overall survival was high (95.2%-97.6%), and axillary recurrence remained low (1.1%-2.3%), with no significant difference compared to radical dissection. Conclusion: SLNB is a feasible, safe, and reliable alternative to radical axillary clearance in the post-NACT setting. Success is maximized through dual tracer mapping, retrieval of at least three nodes, and consideration of tumour biology. These strategies support the continued de-escalation of axillary surgery, reducing patient morbidity while maintaining oncological safety.