Objective:To evaluate the safety and efficacy of sequential consolidation thoracic radiotherapy after first-line chemotherapy combined with immunotherapy for extensive-stage small cell lung cancer (SCLC).Methods:A retrospective analysis of patients with extensive-stage SCLC admitted to Jiangsu Cancer Hospital from January 2019 to September 2022 was conducted. Patients who achieved effective chemotherapy combined with immunotherapy received sequential consolidation thoracic radiotherapy. The safety was evaluated according to the common terminology criteria for adverse events (CTCAE) 5.0 standard, and the overall survival (OS) and progression-free survival (PFS) were analyzed by Kaplan-Meier method.Results:A total of 33 patients were enrolled, with a median age of 66 years (range, 50-79 years). The median follow-up time was 20 months (range, 3-33 months). Fifteen patients (46%) had disease progression, and 12 patients (36%) died. The toxicities mainly included leukopenia, thrombocytopenia, radiation esophagitis, anorexia, and fatigue, etc. Six patients (18%) had grade 4 hematological toxicity, mainly leukopenia. One patient (3%) had grade 3 radiation pneumonitis, and 3 patients (9%) had grade 1-2 radiation pneumonitis. No grade 5 toxicity was observed in all patient groups. The median PFS was 12 months (95% CI=3.9-20.1). The 6-month, 1-year, and 2-year PFS rates were 78%, 49.6%, and 35.6%, respectively. The median OS was 23 months (95% CI=15.98-30.01). The 6-month, 1-year, and 2-year OS rates were 86.2%, 74.5%, and 47.2%, respectively. Conclusions:Sequential consolidation thoracic radiotherapy after first-line chemotherapy combined with immunotherapy is a safe protocol for extensive-stage SCLC. It brings survival benefits to patients by increasing PFS and OS rates.