PDCD1 and non-small cell lung carcinoma: Although there have been modest improvements in therapeutic strategies for early-stage NSCLC over the last two decades, strategies for metastatic NSCLC have evolved with the use of therapies directed against mutant oncoproteins and immune checkpoint inhibitors (ICIs; programmed cell death protein 1 [PD-1] and its ligand [PD-L1]) that promote host antitumor response.