PDCD1 and non-small cell lung carcinoma: The advent of immune checkpoint inhibitors (ICIs) with anti-cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and anti-programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) has provided unprecedented efficacy gains in numerous cancers including non-small cell lung cancer (NSCLC).