CD274 and head and neck squamous cell carcinoma: KEYNOTE-048 was a landmark clinical study performed for r/m HNSCC treatment, which demonstrated that the first-line treatment of r/m HNSCC population with positive programmed cell death ligand 1 (PD-L1) expression with pembrolizumab alone or combined with platinum-containing chemotherapy presented a greater survival benefit than traditional targeted first-line chemotherapy drugs (Burtness et al., 2019).