Therefore, it can be concluded that pembrolizumab plus platinum and 5-fluorouracil is an appropriate first-line therapy for recurrent or metastatic HNSCC, and that pembrolizumab monotherapy is an appropriate first-line therapy for PD-L1-positive recurrent or metastatic HNSCC (9, 93). Here, CD274 is linked to head and neck squamous cell carcinoma.