Background: As most clinical trials evaluating BRAF and MEK inhibitor combination therapy (B + Minh) have been conducted in Western countries, little is known about the effect of B + Minh among East Asian populations. Material and methods: Data from patients with advanced melanoma treated using B + Minh (either dabrafenib + trametinib or encorafenib + binimetinib) were retrospectively collected from 16 institutes in Japan. Response rates, adverse events, patterns of failure and survival were analysed. Results: We analysed 112 of 144 collected patient records and, of these, 14 had acral/mucosal melanoma. The response rate for the entire cohort was 75.0%. There were no statistical differences in response rates between acral/mucosal and cutaneous melanomas (64.3% versus 76.5%), whereas previous treatment using immune checkpoint inhibitors (ICIs) did not affect response (72.7% versus 73.9%) to B + Minh, response to ICI after B + Minh was only 20%. Patients who achieved complete response had the best overall survival rates at 24 months (94.7%). Elevated serum lactate dehydrogenase levels and 3 or more metastatic sites were independently associated with survival. The most common relapse site was the brain (17.9%). More than half of the patients (58.8%) experienced grade III/IV pyrexia. Conclusion: B + Minh was effective among Japanese patients with melanoma, including those with acral/mucosal melanoma. Factors associated with survival were similar to previous Western studies. B + Minh response was not affected by the previous use of ICI; however, vigilance against brain metastasis during B + Minh therapy is required as the brain was our most commonly encountered relapse site.
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