Genomic landscape of cutaneous, acral, mucosal, and uveal melanoma in Japan: analysis of clinical comprehensive genomic profiling data.

Background: Cutaneous melanoma (CM) is the most common type in Caucasians, while acral melanoma (AM) and mucosal melanoma (MM), which are resistant to immunotherapies and BRAF/MEK-targeted therapies, are more common in East Asians. Genomic profiling is essential for treating melanomas, but such data are lacking in Japan.

Methods: Comprehensive genomic profiling data compiled in the Center for Cancer Genomics and Advanced Therapeutics (C-CAT) were analyzed.

Results: A total of 380 melanomas was analyzed, including 136 CM, 46 AM, 168 MM, and 30 uveal melanoma (UM). MM included conjunctival, sinonasal, oral, esophageal, anorectal, and vulvovaginal melanomas. No significant difference in the median tumor mutational burden (TMB) of CM (3.39 mutations/megabase), AM (2.76), and MM (3.78) was the key finding. Microsatellite instability-high status was found in one case. BRAF V600E/K was found in only 45 patients (12%). Key driver mutations in CM were BRAF (38%), NRAS (21%), NF1 (8%), and KIT (10%), with frequent copy number alterations (CNAs) of CDKN2A, CDKN2B, and MYC. AM was characterized by altered KIT (30%), NRAS (26%), and NF1 (11%) and CDKN2A, CDKN2B, CDK4, MDM2, and CCND1 CNAs. MM was characterized by altered NRAS (24%), KIT (21%), and NF1 (17%) and MYC, KIT, and CDKN2A CNAs, with differences based on anatomical locations. UM bore GNAQ or GNA11 driver mutations (87%) and frequent mutations in SF3B1 or BAP1.

Conclusion: The distinct genomic profiling in Japanese patients, including lower TMB, compared to Caucasians, is associated with poorer treatment outcomes. This result underscores the need for more effective therapeutic agents.