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

This study plans to prospectively enroll 43 subjects with extensive-stage small cell lung cancer (ES-SCLC) without malignant pleural effusion from multiple centers. All subjects will first receive low-dose radiotherapy (DT 15 Gy, 1.5 Gy/fraction × 10 fractions, BID). Within one week after radiotherapy completion, subjects will receive 4-6 cycles of systemic chemotherapy (EP or EC regimen) combined with adebrelimab (anti-PD-L1 antibody), followed by adebrelimab maintenance therapy for two years. Through this regimen, we aim to achieve survival outcomes comparable to or even superior to those of the MATCH study from West China Hospital (median PFS 6.9 months, median OS 16.9 months) and the NCT04562337 study from Shandong Cancer Hospital (median PFS 10.1 months, median OS 21.4 months), with manageable toxicity profiles.

Additionally, immunohistochemistry (IHC) will be performed to detect the expression levels of four key transcriptional proteins-YAP1, NEUROD1, ASCL1, and POU2F3-which are used to guide the molecular subtyping of small cell lung cancer. Based on these results, we will investigate the differential efficacy of this treatment regimen across distinct molecular subtypes (A/N/P/Y/I/AN/QN), with the goal of identifying the subject population most likely to benefit from this approach and ultimately better serving clinical practice.

Inclusion criteria

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

Exclusion criteria

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