Current status and future perspectives of immune checkpoint inhibitors in extensive-stage small cell lung cancer

Small-cell lung cancer (SCLC) is a type of neuroendocrine neoplasms with high aggressiveness and poor prognosis. Chemotherapy has been the standard first-line therapy for SCLC over the past several decades. In recent years, results of randomized phase III CASPIAN and IMpower-133 trials indicated that the combination of immune checkpoint inhibitors (ICIs) with platinum-etoposide chemotherapy improved the overall survival (OS) of patients with extensive stage small-cell lung cancer (ES-SCLC), which has transformed the treatment model for ES-SCLC. ICIs combined with chemotherapy has become the new first-line standard treatment of ES-SCLC with the latest research results from CASPIAN and ASTRUM-005 studies. This review summarizes the recent progress of ICIs in the treatment of ES-SCLC and expounds the mode and efficacy of immunotherapy for ES-SCLC. Future research focused on exploring basic SCLC biology and identifying novel predictive biomarkers in response to ICIs in ES-SCLC is essential. Double-ICIs treatment strategies, bispecific antibodies, and ICIs combined with other therapies, such as chemotherapy, radiotherapy, and targeted therapy, represent a new modality and show great promise for the treatment of ES-SCLC, which should achieve greater therapeutic effects through multiple synergistic mechanisms.