CD274 and head and neck squamous cell carcinoma: In 2014, the KEYNOTE-012 study first confirmed the survival benefit in the PD-L1-positive R/M HNSCC population (23), and in 2016, Ferris R L published the results of the phase III trial Checkmate-141, showing that the ORR of nivolumab in R/M HNSCC patients was 13.3%, with was a significant OS benefit in HNSCC patients whose platinum-based therapy had failed (24).