PDCD1 and head and neck squamous cell carcinoma: The increased response rate to pembrolizumab treatment in cases of HPV+ HNSCC programmed cell death Protein 1 (PD-1)–positive patients, 25% vs. only 14% for HPV-HNSCC cases, also suggests the involvement of HPV status in the response to a possible association of PD-1 inhibitors and radiotherapy.