Validation Study of Sentinel Lymph Node Biopsy after Neoadjuvant Chemotherapy in Breast Cancer

This study evaluated the feasibility, accuracy, and oncological safety of sentinel lymph node biopsy (SLNB) in breast cancer patients who initially presented with node-positive (N1/N2) disease and converted to node-negative (ycN0) status following neoadjuvant chemotherapy (NACT). A prospective observational study was conducted at a tertiary center in New Delhi from July 2022 to July 2024. A total of 120 patients underwent dual-dye SLNB (methylene blue + indocyanine green) followed by complete axillary lymph node dissection. SLNB accuracy was assessed via sensitivity, specificity, and false-negative rate (FNR). SLNB was successfully performed in 97.5% of patients. The sensitivity and specificity of SLNB were 86.27% and 100%, respectively, with an overall FNR of 13.72%. A pathological complete response (pCR) was observed in 37.5% of patients, predominantly in HER2-enriched and triple-negative subtypes. SLNB after NACT is a feasible axillary staging method in ycN0 patients, with high identification rates but an FNR exceeding the ideal 10% threshold. Refinements such as targeted axillary dissection and robust radiologic assessment are essential to improve SLNB accuracy and avoid overtreatment.