Tislelizumab Combined With Chemotherapy and Relayed Radiotherapy in First-line Treatment of ES-SCLC

Inclusion Criteria: 1. Age≥18 years old, male or female, signed Informed Consent Form (ICF); 2. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1; 3. Histologically or cytologically confirmed ES-SCLC; 4. No prior systemic treatment for ES-SCLC; 5. At least one measurable (RECIST 1.1) chest lesion capable of 15Gy/5f irradiation; 6. Adequate hematologic and end organ function; Exclusion Criteria: 1. Active leptomeningeal disease or uncontrolled, untreated brain metastasis; 2. Prior therapy with an antibody or drug against immune checkpoint pathways, including but not limited to, anti program death receptor-1 (anti-PD-1), anti-PD-L1, or anti cytotoxic T lymphocyte associated antigen 4 (anti CTLA-4) antibody; 3. Was administered a live vaccine ≤ 4 weeks before treatment; 4. Active autoimmune diseases or history of autoimmune diseases that may relapse; 5. Any condition that required systemic treatment with either corticosteroids or other immunosuppressive medication ≤ 14 days before treatment; 6. With a history of interstitial lung disease, non-infectious pneumonitis, or uncontrolled systemic diseases; 7. Severe chronic or active infections requiring systemic antibacterial, antifungal or antiviral therapy within 2 weeks prior to treatment, including but not limited to tuberculosis infection; 8. Received therapeutic oral or intravenous (IV) antibiotics within 2 weeks prior to starting treatment;