In the past 20 years, the treatment of lung cancer has undergone radical changes, especially with the in-depth development of the molecular pathology of lung cancer and the rise of immunotherapy, including monoclonal antibodies (mAbs) blocking programmed cell death 1 (PD-1)/PD1 ligand 1 (PD-L1) and the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), known as immune checkpoint inhibitors (ICIs). This evidence concerns the gene PDCD1 and lung cancer.