An Evidence-Based Staging System for Mucosal Melanoma: A Proposal.

Abstract

BACKGROUND: There is no widely employed staging system for mucosal melanoma (MuM) that incorporates all anatomic sites. We hypothesized that MuM patients arising from different anatomical sites could be staged using a common approach. METHODS: A prospective database contained 1814 MuM patients with a median follow-up of 5.14 years was employed. Overall survival (OS) was calculated from the time of pathological diagnosis to the date of death from any cause. Multivariate analyses of prognostic variables and OS were performed using the Cox proportional hazard model. RESULTS: For localized MuM, the most significant median OS differences were primary tumors invading submucosa (i.e., T1) versus deeper (i.e., T2/T3/T4): 4.3 versus 3.4, 3.1, and 2.9 years, respectively (p < 0.001). For patients only with regional node metastasis at presentation, the most significant were: 1 versus ≥ 2 regional nodes (N1 vs. N2, 2.5 vs. 2.1 years, p < 0.001). For patients with distant metastasis at presentation, the median OS was 1.5, 1.2, 0.8, and 0.6 years respectively for skin/subcutaneous tissue/distant lymph nodes (M1a), lung metastasis (M1b), all other visceral sites except brain (M1c), and brain (M1d) (p < 0.001). Based on these results, the staging system for MuM is proposed: (1) Stage I: T1N0M0 (median OS, 4.3 years); (2) Stage II: T2-4N0M0 (3.1 years); (3) Stage IIIA: T1-4N1M0 (2.5 years), Stage IIIB: T1-4N2M0 (2.1 years); (4) Stage IV: TanyNanyM1 (0.9 years) (p < 0.001). CONCLUSIONS: A single, unified, staging system for mucosal melanoma inclusive of all anatomical primary tumor sites can harmonize staging of MuM and the design of clinical trials.