Immunotherapy Advances in Small Cell Lung Cancer

Small cell lung (SCLC) is a refractory cancer characterized by rapid growth and extensive early metastasis. About 70% of patients are already in the extensive stage at the time of diagnosis. Despite the high response rate to platinum-contained first-line chemotherapy, almost all patients subsequently experienced inevitable recurrence and had poor response to second-line treatment. The high mutation load and immunogenicity of SCLC suggest that immunotherapy may be effective for SCLC patients. Over the past few years, several clinical trials have evaluated the efficacy of checkpoint inhibitors [mainly cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and programmed death 1 (PD-1)/programmed death ligand-1 (PD-L1) inhibitors] in SCLC patients and demonstrated promising survival prospects. This article reviewed the clinical studies of immune checkpoint inhibitors (ICIs) in the first-line, maintenance and second or more line treatment of SCLC. Besides, predictive biomarkers were discussed to select suitable patients for immunotherapy effectively.