CTLA4 and non-small cell lung carcinoma: Immunotherapy using checkpoint inhibitory monoclonal antibodies blocking programmed cell death 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), either as single agents or in combination, have led to a revolution in the treatment of several solid tumors, including NSCLC.