Fortunately, the emergence of immune checkpoint inhibitors (eg, cytotoxic T-lymphocyte-associated protein-4 [CTLA-4], programmed death 1 [PD-1]/ programmed cell death-ligand 1 [PD-L1], lymphocyte-activation-gene-3 [LAG-3], T cell immunoglobulin and mucin protein-3 [TIM-3]) has brought breakthroughs in the treatment of SCLC in recent years. Here, CTLA4 is linked to small cell lung carcinoma.