PDCD1 and non-small cell lung carcinoma: Combination strategies of immune checkpoint inhibitors (ICIs) that target cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed cell death protein 1 (PD-1), and its ligand (PD-L1) with standard chemotherapy agents are a rapidly evolving treatment modality for stage IV non-small cell lung cancer (NSCLC) [1,2].