Adjuvant Immune Checkpoint Inhibitor Versus Observation After Neoadjuvant Immunochemotherapy and Surgery in High-Risk NSCLC

Inclusion Criteria: 1. Male or female participants aged 18 to 75 years. 2. Histologically or cytologically confirmed non-small cell lung cancer. 3. Completion of 2 to 4 cycles of neoadjuvant immune checkpoint inhibitor therapy combined with chemotherapy, followed by complete (R0) surgical resection. 4. At least one of the following protocol-defined high-risk features for postoperative recurrence: * Pathologic lymph-node involvement; * Postoperative pathologic T2 or higher disease; * Failure to achieve a major pathologic response, defined as more than 10% residual viable tumor cells in the primary tumor; * Pleural invasion; * Intravascular tumor emboli; * High-risk histologic components, including solid, micropapillary, or adenosquamous components; * Detectable molecular residual disease. 5. For participants with lung adenocarcinoma, absence of sensitizing EGFR mutations and ALK rearrangements. Molecular testing is not mandatory for participants with squamous cell carcinoma according to the current protocol. 6. Eastern Cooperative Oncology Group performance status of 0 or 1. 7. Adequate organ function within 7 days before randomization, as demonstrated by all of the following: * Hemoglobin of at least 90 g/L; * Absolute neutrophil count of at least 1.5 × 10\^9/L; * Platelet count of at least 75 × 10\^9/L; * Total bilirubin no greater than 1.5 times the upper limit of normal; * Alanine aminotransferase and aspartate aminotransferase no greater than 2.5 times the upper limit of normal; * Serum creatinine no greater than 1.5 times the upper limit of normal or creatinine clearance of at least 60 mL/min; * Left ventricular ejection fraction of at least 50%; * International normalized ratio or prothrombin time no greater than 1.5 times the upper limit of normal. 8. Women of childbearing potential must have a negative pregnancy test within 7 days before the first dose and must agree to use effective contraception during the study and for 3 months after the last dose of study treatment. Male participants with partners of childbearing potential must agree to use effective contraception during the study and for 8 weeks after the last dose. 9. Ability to understand the study requirements, willingness to provide written informed consent, and ability to comply with study treatment and follow-up procedures. Exclusion Criteria: 1. Small cell lung cancer or non-small cell lung cancer containing a small cell carcinoma component. 2. Incomplete resection, including R1 or R2 resection, or salvage surgery. 3. Clinically significant malnutrition as determined by the investigator. 4. A history of clinically significant immune-related adverse events during prior treatment, including grade 3 or higher immune-mediated pneumonitis, myocarditis, or another serious immune-related adverse event that, in the investigator's judgment, makes further immune checkpoint inhibitor therapy unsafe. 5. Signs, symptoms, or a known history of clinically significant interstitial lung disease. 6. Any severe or uncontrolled concurrent medical condition, including: * Inadequately controlled hypertension; * Grade 2 or higher myocardial ischemia, myocardial infarction, clinically significant arrhythmia, corrected QT interval of at least 480 milliseconds, or New York Heart Association class II or higher heart failure; * Active or uncontrolled infection of grade 2 or higher; * Decompensated liver disease, active hepatitis, or chronic viral hepatitis requiring antiviral therapy; * Renal failure requiring hemodialysis or peritoneal dialysis; * Known human immunodeficiency virus infection, another acquired or congenital immunodeficiency disorder, or a history of organ transplantation; * Poorly controlled diabetes mellitus, defined as fasting blood glucose greater than 10 mmol/L; * Urine protein of 2+ or greater with a 24-hour urinary protein level greater than 1.0 g; * Clinically significant coagulation abnormalities or an increased risk of bleeding; * A seizure disorder requiring treatment. 7. A concurrent active malignancy, except for malignancies specifically permitted by the final protocol. 8. An active autoimmune disease or another immune-mediated disease requiring systemic treatment. 9. Long-term treatment with systemic immunosuppressive therapy or systemic corticosteroids, except for protocol-permitted physiologic replacement therapy. 10. An active psychiatric disorder, cognitive impairment, or another condition that would prevent provision of informed consent or adherence to study treatment and follow-up. 11. Any other condition that, in the investigator's judgment, makes the participant unsuitable for the study.