Evidence for a better nodal staging system for melanoma: the clinical relevance of metastatic disease confined to the sentinel lymph nodes.

Abstract

The hypothesis tested in this study was whether patients with stage III metastatic melanoma confined to their sentinel lymph nodes (SLNs) had a more favorable prognosis than patients who had SLN and non-SLN (NSLN) metastases. Patients were identified who were clinically negative in their regional basins but with lymphatic mapping were found to have positive SLNs (331 patients). All patients subsequently underwent a complete lymph node dissection of the lymphatic basin involved, and the total number of metastatic SLNs and NSLNs were documented. As the regional metastatic disease involves NSLNs, disease-free survival (DFS) and overall survival (OS) decreases. For patients with a total of 2 nodes positive, those with disease confined to the SLNs had a significant better prognosis (DFS and OS: P < .00001) than those in whom 1 SLN and 1 non-SLN was involved. This difference was apparent for those patients with N2 and N3 disease (2 or more nodes positive in their regional basin). A multivariate regression analysis that included Breslow thickness, ulceration, number of positive nodes, and NSLN positivity showed that NSLN positivity (P = .0019) was the most powerful predictor of DFS and OS. When metastatic melanoma overwhelms the SLN and involves NSLNs, the biologic behavior changes to portend a worse survival, regardless of the total node count positive. These data make the argument that the current N staging system should be changed to incorporate SLN vs NSLN involvement.