Adebrelimab Maintenance Therapy for LS-SCLC Post Induction Chemo-Adebrelimab Plus CRT or CRT Alone

The study comprises two cohorts (A and B). Cohort A first receives two cycles of induction therapy combining PD-L1 inhibitors with chemotherapy, followed by two cycles of concurrent chemoradiotherapy and subsequent maintenance therapy with PD-L1 inhibitors. Cohort B first undergoes four cycles of concurrent chemoradiotherapy followed by maintenance therapy with PD-L1 inhibitors. Both cohorts continue treatment until disease progression or intolerable toxicity occurs.

Inclusion criteria

• Age: 18-75 years old, male or female;
• Patients with pathologically confirmed localized small cell lung cancer (as defined by the Veterans Administration Lung Study Group, VALG staging);
• No anticipated need for tumor resection during the study period (including patients unsuitable for surgery or unwilling to undergo surgery);
• No prior treatment for localized small cell lung cancer;
• Presence of measurable tumor target lesions (meeting RECIST 1.1 criteria);
• Expected survival > 3 months;
• ECOG PS: 0-1;
• Normal major organ function;

• Complete blood count (CBC) (without transfusion or hematopoietic growth factor correction within 14 days):

Hemoglobin (Hb) ≥ 90 g/L; Absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L; Platelet count (PLT) ≥ 100 × 10⁹/L; White blood cell count (WBC) ≥ 3.0 × 10⁹/L;

• Biochemical tests:

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5×ULN (≤ 5×ULN for patients with liver metastases); Serum total bilirubin (TBIL) ≤ 1.5×ULN (≤ 3×ULN for subjects with Gilbert syndrome); Serum creatinine (Cr) ≤ 1.5×ULN or creatinine clearance ≥ 50 mL/min;

• Coagulation function:

Activated partial thromboplastin time (APTT), International Normalized Ratio (INR), Prothrombin time (PT) ≤ 1.5×ULN;

• Doppler ultrasound assessment:

Left ventricular ejection fraction (LVEF) ≥50%;

• Women of childbearing potential must have a negative pregnancy test (βHCG) prior to treatment initiation. Women of childbearing potential and males (who have sexual intercourse with women of childbearing potential) must agree to use effective contraception continuously during treatment and for 6 months after the last dose.
• Patients voluntarily participate in this study and sign an informed consent form.

Exclusion criteria

• Mixed SCLC and extensive-stage SCLC;
• History of other malignancies within the past 5 years or concurrent malignancies, except for cured basal cell carcinoma of the skin, cervical carcinoma in situ, or superficial or non-invasive bladder cancer;
• History of uncontrollable psychiatric disorders or severe intellectual or cognitive impairment;
• Active, known, or suspected autoimmune disease; however, subjects with hypothyroidism requiring only hormone replacement therapy or skin conditions not requiring systemic treatment (e.g., vitiligo, psoriasis, or alopecia) are eligible;
• Subjects with any severe and/or uncontrolled medical conditions, including:

• Subjects with uncontrolled blood pressure (systolic ≥150 mmHg or diastolic ≥100 mmHg);
• Subjects with ≥ Grade 2 myocardial ischemia or myocardial infarction, arrhythmias (including male QTc ≥ 450 ms or female QTc ≥ 470 ms), and ≥ Grade 2 congestive heart failure (New York Heart Association [NYHA] classification);
• Severe unhealed wounds, ulcers, or fractures;
• History of psychiatric drug abuse, alcoholism, or illicit drug use;
• Active hepatitis (HBV reference: HBsAg positive with HBV DNA levels exceeding upper normal limit; HCV reference: HCV antibody positive with HCV viral load exceeding upper normal limit);
• Human Immunodeficiency Virus (HIV, HIV 1/2 antibody) positive;
• Patients unable to comply with the study protocol or participate in follow-up visits;
• Patients deemed unsuitable for this trial by the investigator.