Sentinel lymph node status and oncological outcomes of high-risk and low-risk cutaneous primary melanoma.

INTRODUCTION: The role of sentinel lymph node biopsy (SLNB) in clinically node-negative melanoma has been questioned in the era of effective adjuvant immunotherapy. We evaluated the staging and prognostic value of SLNB in a single-centre cohort, with emphasis on patients with “high-risk” primary tumours. METHODS: We retrospectively analysed 300 consecutive patients with cutaneous melanoma who underwent wide local excision with SLNB at a tertiary melanoma centre (April 2018–April 2023). Patients were stratified by AJCC 8th edition T stage into low-risk (T1–T3a) and high-risk (T3b–T4b) groups. Outcomes included SLN positivity, recurrence, and disease-free survival (DFS). DFS was assessed using Kaplan–Meier methods with log-rank testing; restricted mean survival time (RMST) was calculated to 3 years. In high-risk patients with available data, the Melanoma Institute of Australia sentinel node risk tool was evaluated for discrimination and calibration. RESULTS: Median age was 60.7 years and 51.3% were male. Overall SLN positivity was 22.0% (66/300) and was higher in high-risk than low-risk melanoma (31.5% [28/89] vs. 18.0% [38/211], P = 0.009). Recurrence occurred in 16.0% (48/300), more frequently in high-risk patients (31.5% vs. 9.5%). Estimated DFS at 1 and 3 years was 96.6% and 81.8% for low-risk melanoma versus 87.9% and 68.6% for high-risk melanoma (log-rank P < 0.001); RMST to 3 years favoured the low-risk group by 115.9 days (95% CI 20.8–213.3). SLNB resulted in substantial stage migration in high-risk clinically node-negative patients, identifying pathological stage IIIC disease in 31.5% (28/89) who would otherwise be classified as stage IIB/IIC. CONCLUSION: SLNB continues to provide clinically important staging and prognostic information, particularly in high-risk clinically node-negative melanoma where occult nodal disease is common. Omitting SLNB risks systematic understaging and loss of prognostic resolution.