This study is a prospective, single arm, phase II clinical trial. We plan to include 36 newly diagnosed ES-SCLC patients who meet the inclusion criteria and receive induction therapy (tislelizumab+EP regimen, 4-6 cycles). After completing the induction therapy, efficacy evaluation will be conducted. Patients with remission will receive tislelizumab combined with consolidation chest radiotherapy (TRT) sequentially. After the consolidation therapy is completed, they will receive tislelizumab maintenance therapy until disease progression, intolerable toxicity, or withdrawal of informed consent occurs, whichever occurs first. The treatment duration will not exceed 2 years.