PDCD1 and head and neck squamous cell carcinoma: In another single-arm, multicenter, phase II trial (jRCTs051200040), combination chemotherapy with paclitaxel and cetuximab was administered to 35 recurrent/metastatic (R/M)-HNSCC patients previously treated with platinum-based chemotherapy and PD-1 (programmed cell death protein 1) antibody.