PDCD1 and head and neck squamous cell carcinoma: KEYNOTE-048 (NCT02358031), a randomized open-label phase 3 study comparing the humanized monoclonal antibody pembrolizumab (Keytruda) targeting PD-1 alone or in conjunction with chemotherapy (platinum and 5-fluorouracil) against cetuximab with chemotherapy, demonstrated overall survival improvement in both treatment arms over standard-of-care therapy in recurrent or metastatic HNSCC [27].