The use of blue dye alone for sentinel lymph node biopsy after neoadjuvant chemotherapy in patients with initially node-positive breast cancer

False-negative sentinel lymph node biopsy (SLNB) rates following neoadjuvant chemotherapy (NACT) in initially node-positive (cN1/2) breast cancer patients are high, but decrease when lymph nodes are clipped, ≥3 sentinel lymph nodes (SLN) are removed or dual-tracer localization (radioisotope and blue dye) is used. Radiotracer, however, is often unavailable and outcomes with blue dye alone are unknown. Initially cT1-4, cN1/2 patients treated with NACT in 2013–2023 who underwent SLNB using blue dye alone were evaluated regarding SLN identification, axillary recurrence, disease-free and overall survival rates. Of 119 patients included, 19 remained cN1/2 after NACT. SLNB was performed using blue dye alone in 100 ycN0 cases (84%), with an identification rate of 96%. The SLN was negative in 70/119 cases (i.e. 59% avoided axillary dissection). The number of SLN detected was ≥3 in 55/70 cases (78%) (median 3.1; 1–6). Median age was 49 years (25–84). Most were T2 (n = 40, 57.1%), N1 (n = 64, 91.4%). Predominant subtypes were ERBB2 (52.9%) and triple-negative (20%). No axillary recurrence occurred over a median 36-month period. Five-year disease-free and overall survival were, respectively, 85.9% (95%CI: 74–99.8) and 96.3% (95%CI: 89.4–100). The ERBB2 subtype (1.99, 95%CI: 1.02–3.85, p = 0.04) and N1 lymph node status (2.58, 95%CI: 1.54–9.10, p = 0.03) were associated with a greater likelihood of undergoing SLNB alone without axillary dissection. SLNB with blue dye alone following NACT in initially cN1/2 patients avoided axillary dissection in almost 60% of cases, with no recurrences during the period evaluated. Longer follow-up studies are necessary.