CD274 and head and neck squamous cell carcinoma: In the phase III KESTREL trial (NCT02551159), first-line durvalumab monotherapy or durvalumab plus tremelimumab was compared with EXTREME in recurrent/metastatic HNSCC, and archival tumors or blood were assayed for PD-L1, blood tumor mutational burden (bTMB), and neutrophil-to-lymphocyte ratio (NLR).