CTLA4 and non-small cell lung carcinoma: Combination immunotherapy approaches targeting PD-1 and CTLA-4 using ipilimumab and nivolumab have led to their use in a variety of tumors types, including melanoma, non-small cell lung cancer, renal cell carcinoma, esophageal squamous cell carcinoma, microsatellite-instability-high or mismatch repair deficient colorectal cancer, malignant pleural mesothelioma, and hepatocellular carcinoma1–3,6–9.