Efficacy of checkpoint inhibition in advanced acral melanoma

e21527 Background: Recent data in Japanese patients suggest poor outcomes for anti-PD1 in acral melanoma (AM), with no data available on combination treatment. The objective of this study was to analyze the efficacy of anti-PD1 monotherapy and anti-PD1 and anti-CTLA4 combination therapy in these patients. Methods: Our study population consisted of patients registered in the nationwide prospective Dutch Melanoma Treatment Registry between 2014 and 2020. We calculated objective response rate (ORR) in all unresectable stage III and IV AM and nonacral cutaneous melanoma (NAM) patients treated with anti-PD1, and combination anti-PD1 and anti-CTLA4. Progression-free survival (PFS), and overall survival (OS) were estimated for first-line treated patients. A Cox proportional hazard analysis was performed to adjust for potential confounders. Results: Nighty-five AM patients received at least one dose of anti-PD1 monotherapy, of whom 58 (61%) as first-line treatment. ORR was 28% (complete res...