Risk-based stratification in head and neck mucosal melanoma

Background: Head and neck mucosal melanoma (HNMM) is a rare and aggressive disease with a high metastatic potential. Two staging systems are currently available: one specific to HNMM (mmTNM) and one specific to primary tumour sites (sccTNM). Our main objective was to assess the prognostic value of both of these classifications in order to allow accurate risk-based classification.

Methods: We performed a retrospective cohort study of patients with HNMM treated consecutively between 2000 and 2017. All of the patients were restaged using the mmTNM and the sccTNM. A prognostic analysis was carried out according to both staging systems.

Results: There were 96 patients with an HNMM in our cohort, of whom 80 underwent surgical treatment followed by radiotherapy. The median overall survival (OS) and progression-free survival (PFS) for the operated patients were 39 months (95% CI, 21.6-56.4 months) and 18 months (95% CI, 6.5-29.5 months), respectively. A paranasal sinus localization was associated with lower survival compared to a nasal cavity primary localization (p < 1 0^-4). Both of the classifications correlated with OS, PFS, and distant metastasis-free survival. High-risk HNMM were characterized as T4/stage IV by the mmTNM and T3-4/stage III-IV by the sccTNM. Given the primary tumour location, both TNM classifications were suitable for risk-stratification of sinonasal mucosal melanomas. However, combining both TNM, we defined new stages mmT3A and mmT3B according to sccTNM with a more accurate risk stratification (p < 1 0^-4).

Conclusions: Both of the classifications should be combined, in order to improve the risk-stratification of patients with HNMM.