PDCD1 and head and neck squamous cell carcinoma: In 2019, both the US Food and Drug Administration and the European Commission granted approval for PD-1 inhibition as a first-line treatment for patients with metastatic or unresectable, recurrent head and neck squamous cell carcinoma (HNSCC) as monotherapy or in combination with platinum and 5-fluorouracil (5-FU) chemotherapy.