Pembrolizumab (a programmed cell death-1 inhibitor, a PD-1 inhibitor) alone or in combination therapy improved prognosis compared to standard therapy in programmed cell death-ligand 1 (PD-L1)-positive patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) in a multicenter clinical trial (KEYNOTE-048) (5). This evidence concerns the gene PDCD1 and head and neck squamous cell carcinoma.