Low-dose Thoracic Radiotherapy Followed by Adebrelimab Plus Chemotherapy, and Then Sequential Maintenance Therapy With Adebrelimab for Extensive-stage Small Cell Lung Cancer

Inclusion Criteria:

1. Age ≥18 years and ≤75 years;
2. Histologically or cytologically confirmed SCLC;
3. No malignant pleural effusion or pericardial effusion;
4. No prior history of thoracic radiotherapy or thoracic surgery;
5. No prior systemic anti-tumor therapy;
6. ECOG performance status 0-2, with a life expectancy of ≥12 weeks;
7. At least one measurable lesion per RECIST 1.1 criteria;
8. No history of interstitial pneumonia;
9. No history of immune-related pneumonitis;
10. No history of autoimmune diseases;
11. No history of significant active pulmonary infection;
12. No use of corticosteroid therapy within 14 days prior to enrollment;
13. No Grade ≥3 hematologic toxicity or hepatic/renal impairment;
14. No brainstem metastases and no significant neurological symptoms;
15. For subjects with coexisting HBV/HCV infection, hepatic impairment ≤ Grade 1 after prior active antiviral therapy;
16. All subjects have provided written informed consent;

Exclusion Criteria:

1. Presence of interstitial pneumonia or infectious fever prior to treatment;
2. Comorbid autoimmune diseases or long-term oral corticosteroid use (including those who received oral corticosteroids within 14 days prior to treatment);
3. Prior history of thoracic radiotherapy or thoracic surgery;
4. Presence of Grade ≥3 hematologic toxicity or hepatic/renal impairment;
5. Hypersensitivity to adebrelimab;
6. Significant respiratory symptoms that preclude tolerance to radiotherapy;
7. Active hepatitis B or C infection, currently on antiviral therapy, and with liver function impairment of Grade 2 or above;
8. Presence of pleural effusion or pericardial effusion;