Abstract
OBJECTIVES: The purpose of this study is to compare genetic mutations, tumor mutation burden (TMB), and the effects of molecular targeted drugs and immune checkpoint inhibitors (ICIs) in head and neck mucosal melanoma (HNMUM) with those in skin melanoma (SKM) and ocular melanoma (OM). METHODS: Data were analyzed for 72 consecutive patients with HNMUM, including 366 with SKM and 31 with OM, registered at the Japan National Cancer Center, Center for Cancer Genomics and Advanced Therapeutics (C-CAT) between June 2019 and October 2023. Genetic alterations and TMB were determined by FoundationOne CDx next-generation sequencing. RESULTS: The top 10 mutations in HNMUM were RAD21 (47.2%), NBN (45.8%), MYC (40.3%), LYN (31.9%), NRAS (29.1%), IRF4 (23.6%), DAXX (22.2%), KIT (22.2%), NOTCH3 (20.8%), and DDR1 (19.4%), with 16.6 ± 0.8 (mean ± SEM) mutations/individual. In SKM, BRAF (p = 0.04) mutation was associated with a significantly better prognosis. The TMB values were 5.7 ± 2.1 (mean ± SEM) in HNMUM, 4.1 ± 0.2 in SKM, and 3.4 ± 0.9 in OM, with no significant differences among the three groups. The median survival time for patients with distant metastases was 803 (95% confidence interval: 539-NA) days for HNMUM, 1413 (831-2172) days for SKM, and 1138 (438-NA) days for OM. CONCLUSIONS: The top 10 mutations in HNMUM are closer to those in OM than those in SKM. There was no significant difference in TMB values or survival rates with regard to the therapeutic effect of ICIs among the diseases, which suggests that current treatment of HNMUM with ICIs is appropriate. LEVEL OF EVIDENCE: 3 Laryngoscope, 135:134-139, 2025.