CD274 and head and neck squamous cell carcinoma: In KEYNOTE-048 study, pembrolizumab combined with chemotherapy in total population or pembrolizumab alone in participants with PD-L1 combined positive score (CPS)≥1 obtained better survival benefit than EXTREME regimen (cetuximab plus cisplatin/5-fluorouracil) in the first-line treatment for patients with R/M HNSCC 1.