Sentinel Lymph Node Biopsy in T4 Melanoma: An Important Risk-Stratification Tool

Background: Sentinel lymph node biopsy (SLNB) is a sensitive test for detecting subclinical nodal metastatic disease in patients with melanoma without evidence of lymph node involvement. The prognostic significance of SLN positivity in patients with melanoma >4 mm thick (T4) is unclear. The survival curves in the current AJCC staging system suggest that the status of the SLN is not predictive of outcome for patients with T4 melanoma. Methods: Patients with primary T4 melanoma without clinical nodal involvement who underwent SLNB between 2002 and 2012 at Peter MacCallum Cancer Centre were included in the analysis with chart review performed to collect clinical, pathological, and outcome data. A meta-analysis was performed including similar studies of SLNB in T4 melanoma, which reported overall survival (OS) data. Results: Of 217 patients who underwent SLNB, 78 patients had a positive SLN (36 %). The 5-year OS for SLNB negative and positive patients was 68 and 45 %, respectively [hazard ratio (HR) 2.82; 95 % CI 1.76–4.51; P = .001]. On multivariate analysis, the only predictors of OS were the status of the SLN (HR 2.88; 95 % CI 1.75–4.73) and the presence of satellitosis (HR 2.59; 95 % CI 1.30–5.76). The meta-analysis identified 10 studies that met the inclusion criteria. All reported similar findings, demonstrating a significant difference in OS according to sentinel lymph node status; the pooled analysis of 2104 patients demonstrated an overall HR for OS according to SLNB status of 2.3 (95 % CI 1.95–2.71). Conclusions: SLNB provides important prognostic information for patients with T4 melanoma. This information is important when stratifying patients for clinical trials.