Immunotherapy combined with chemotherapy has emerged as the standard of care for patients with extensive-stage small cell lung cancer (ES-SCLC). The incorporation of thoracic radiotherapy can enhance treatment efficacy. Currently, the main types of research investigating immunotherapy combined with thoracic radiotherapy for untreated ES-SCLC are concurrent radiotherapy and sequential radiotherapy. The aim of this study is to evaluate the efficacy of adebelizumab in combination with chemotherapy, when administered concurrently with radiotherapy versus sequentially with radiotherapy, as a first-line treatment for ES-SCLC.