Adebrelimab plus etoposide capsules as maintenance therapy for extensive-stage small cell lung cancer

Inclusion Criteria:

1. Voluntary participation with signed informed consent and good compliance for follow-up.
2. Age between 18 and 75 years old.
3. Histologically or cytologically confirmed extensive-stage small cell lung cancer (ES-SCLC) according to the AJCC 8th edition or VALG phase II staging criteria.
4. ECOG performance status score: 0 to 2.
5. Absence of disease progression after receiving 4-6 cycles of platinum-based chemotherapy combined with Adebrelimab induction therapy.
6. Recovery of non-hematologic adverse reactions to grade 1 (except for alopecia, skin pigment changes, or as determined by the investigator) following induction therapy.
7. Time from the end of induction treatment (last dose) to initiation of maintenance treatment ≤ 6 weeks.
8. At least one measurable lesion assessed by the investigator according to RECIST 1.1.
9. Normal function of major organs, meeting the following criteria:

(1)Bone marrow function: Absolute neutrophil count (ANC) ≥ 1.5×10\^9/L (grade 1 according to CTCAE 5.0); platelets ≥ 100×10\^9/L; hemoglobin \> 80g/L.

(2)Renal function: Creatinine ≤ 1.5 times the upper limit of normal (ULN), grade 1 according to CTCAE. Note: If creatinine is greater than 1.5 times the ULN, creatinine clearance must be \> 50ml/min.

(3)Liver function: Bilirubin ≤ 1.5 times ULN (grade 1 according to CTCAE), patients with Gilbert's syndrome bilirubin ≤ 3.0 times ULN; AST and ALT ≤ 3.0×ULN.

(4)Coagulation indicators: International normalized ratio (INR) ≤ 1.55 (if the patient is receiving a stable dose of therapeutic warfarin or low molecular weight heparin, INR is usually between 2 and 3), PTT \< 1.2 times ULN.

10.Women of childbearing potential must agree to use contraception during the study and for 6 months after the end of the study (such as an intrauterine device, contraceptive pills, or condoms); serum or urine pregnancy test must be negative within 1 week before enrollment, and must be non-lactating patients; men must agree to use contraception during the study and for 6 months after the end of the study.

Exclusion Criteria:

1. Limited-stage small cell lung cancer (SCLC);
2. Histologically or cytologically confirmed mixed histology SCLC;
3. Prior treatment with anti-angiogenic agents;
4. Conditions that may affect oral drug intake, such as inability to swallow, chronic diarrhea, or intestinal obstruction;
5. Major surgery, open biopsy, or significant traumatic injury within 4 weeks prior to enrollment;
6. Participation in another investigational drug clinical trial within 4 weeks prior to enrollment;
7. Relevant medical history:

(1)Untreated or symptomatic brain metastases or spinal cord compression; (2)Concurrent active malignancy requiring treatment; (3)Active autoimmune disease or immunodeficiency, or a history of such conditions, including but not limited to autoimmune hepatitis, interstitial lung disease, uveitis, rheumatoid arthritis, inflammatory bowel disease, hypophysitis, vasculitis, or nephritis.Exceptions include: patients with stable disease not requiring systemic immunosuppressive therapy, such as type I diabetes mellitus, hypothyroidism controlled with hormone replacement therapy, or skin disorders not requiring systemic treatment (e.g., vitiligo, psoriasis, or alopecia), or those with no external triggering factors and a low risk of recurrence; (4)History of psychiatric or substance abuse disorders that would interfere with study compliance; 8.Presence of any severe and/or uncontrolled comorbid conditions, including but not limited to:

1. Uncontrolled hypertension (systolic BP ≥150 mmHg or diastolic BP ≥100 mmHg);
2. Myocardial ischemia or infarction of grade I or higher, arrhythmias (including QTc ≥450 ms in males, ≥470 ms in females), congestive heart failure of NYHA class ≥2, or left ventricular ejection fraction (LVEF) \<50% on echocardiogram;
3. Decompensated diabetes mellitus or other contraindications requiring high-dose corticosteroids;
4. Exacerbation of chronic obstructive pulmonary disease (COPD) or other serious respiratory disorders requiring hospitalization;
5. Active or uncontrolled severe infection (≥CTCAE grade 2);
6. Uncontrolled pleural, pericardial, or peritoneal effusion requiring repeated drainage;
7. Liver cirrhosis, decompensated liver disease, active hepatitis, or chronic hepatitis requiring antiviral treatment;
8. Renal insufficiency: urine protein ≥++ on routine urinalysis and 24-hour urine protein \>1.0 g confirmed; 9.Severe infection within 4 weeks before the first dose, including but not limited to infectious complications, bacteremia, severe pneumonia requiring hospitalization, or infections requiring intravenous antibiotics, antifungals, or antivirals; or unexplained fever \>38.5°C during screening or prior to first dose; 10.Grade III-IV immune-related adverse events (irAEs) during the induction phase with PD-L1 inhibitors; 11.Active brain or leptomeningeal metastases at enrollment; Exception: patients who received prior treatment (e.g., radiotherapy) for brain or leptomeningeal metastases during or before induction and had stable disease on imaging for at least 4 weeks prior to enrollment, discontinued systemic steroid therapy (≤10 mg/day prednisone or equivalent) for more than 4 weeks, and are asymptomatic, may be eligible; 12.Patients deemed by the investigator to be unable or unlikely to comply with the study protocol, restrictions, or requirements.