Abstract 5764: Genomic profiling of cutaneous, acral and mucosal melanomas in Chinese populations

Abstract

Abstract Background: Targeted therapies and immunotherapies have significantly improved the survival of patients with cutaneous melanoma. Nevertheless, patients with acral and mucosal melanomas show limited benefit. The proportion of acral and mucosal subtypes are much higher in Chinese populations than Caucasians. Therefore, it is of great interest to detail the genomic features of acral and mucosal melanomas and compare these with cutaneous melanoma. Methods: A total of 111 Chinese patients with melanoma treated in Union Hospital, Tongji Medical College, Huazhong University of Science and Technology were enrolled in this study, comprising 32 cutaneous(28.8%), 41 acral(36.9%) and 26 mucosal(23.4%) subtypes. NGS-based genomic profiling of major cancer-related genes was performed on formalin-fixed, paraffin-embedded (FFPE) tumor tissue specimens with matched blood samples. Tumor mutational burden (TMB) was calculated based on somatic nonsynonymous missense mutations. Results: The most commonly mutated genes of cutaneous melanoma include BRAF(48%), CDKN2A(41%), CDKN2B(41%), NRAS(22%) and PTEN(22%). In acral melanoma patients, the mutation rate of BRAF was 10% while NRAS(31%), CDKN2A(21%), EMSY(21%), KIT(18%), CCND1(18%)) and NF1(18%) were frequently mutated. Mucosal melanomas were found most commonly to have mutations in CDKN2A(36%), KIT(32%), CDKN2B(28%), PDGFRA(24%), KDR(20%) and BRAF(16%). In acral and mucosal subtypes, the overall mutation rates of BRAF were significantly lower while the relative proportions of non-V600 mutations were higher as compared to cutaneous subtype. These may explain the less significant survival benefit of BRAFi+/-MEKi in acral and mucosal melanomas. In contrast, KIT mutations including SNVs and amplification, were enriched in acral and mucosal melanomas. Acral melanomas had lower mutation load than mucosal melanomas(2.42 Muts/Mb vs 4.84 Muts/Mb, p=0.0002), while cutaneous melanomas(4.03 Muts/Mb) did not differ from other subtypes in mutation burden. Additionally, patients with TERT, APC and FAT1 gene mutations had a significantly higher TMB than patients with wild-type genes respectively, indicating more activated anti-tumor immune profiles and suggesting therapeutic benefit from immune checkpoint inhibitors. Conclusions: We conducted a direction comparison of comprehensive genomic profiles of different melanoma subtypes among Chinese patients. The genomic alterations identified in our study may provide reference to discover potential strategies for targeted therapy and immunotherapy in acral and mucosal melanomas. Citation Format: Jing Chen, Ting Ye, Li Fan, Jieying Zhang, Rubo Cao, Yanshen Liu. Genomic profiling of cutaneous, acral and mucosal melanomas in Chinese populations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5764.