Keywords: CR, complete response; CT, computed tomography; FDA, US Food and Drug Administration; ICB, immune checkpoint blockade; MCC, Merkel cell carcinoma; MCPyV, Merkel cell polyomavirus; Merkel cell carcinoma; ORR, objective response rate; PD-L1, programmed death ligand 1; PET, positron emission tomography; PFS, progression-free survival; SUV, standardized uptake values; TVEC, talimogene laherparepvec; advanced Merkel cell carcinoma; durable response; immunotherapy; oncolytic virus; regionally advanced Merkel cell carcinoma; talimogene laherparepvec.