In recent years, immunotherapy has shown good antitumor activity, especially programmed death receptor-1/ligand-L1 (PD-1/L1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) Checkpoint inhibitors have changed the pattern of tumor treatment, and SCLC has high immunogenicity, high mutation load and other favorable immune factors, so immuno-checkpoint inhibitors may become an important breakthrough in SCLC treatment. This evidence concerns the gene CTLA4 and neoplasm.