Consolidation Serplulimab Following Concurrent Chemoradiotherapy for LS-SCLC Patients

All eligible patients after screening will receive up to four cycles chemotherapy. Recommended regimens are etoposide 100 mg/m2 intravenously on day 1-3 in combination with cisplatin 75 mg/m2 intravenously on day 1 or carboplatin AUC=5 every 3 weeks. A total of 45Gy in 15 fractions over 3 weeks will be delivered. PCI is routinely scheduled for patients without progression after chemoradiotherapy, and hippocampal avoidance is highly recommended. 25Gy in 10 fractions over 2 weeks to the brain will be prescribed. Intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) technique are required. Patients without disease progression will receive an intravenous infusion of serplulimab 300mg every 3 weeks. Treatment of serplulimab should be continued until disease progression, intolerable toxicity, withdrawal of consent, or to a maximum of 1 year. Continuation of immunotherapy after disease progression is acceptable per investigators' discretion. The investigator and IRRC respectively assess the tumor images according to RECIST 1.1.