Consolidation Radiotherapy vs. Observation in Oligoresidual Advanced Non-Small Cell Lung Cancer After Chemo-Immunotherapy

Inclusion Criteria: 1. Voluntary signed written informed consent and compliance with protocol requirements; 2. Age ≥ 18 years; 3. Expected survival time ≥ 3 months; 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1; 5. Histologically or cytologically confirmed advanced non-small cell lung cancer; 6. After receiving 4-6 cycles of first-line platinum-based chemotherapy combined with immunotherapy, PET-CT evaluation shows no disease progression, with no more than 5 lesions not meeting criteria for complete metabolic response, involving no more than 3 organs; 7. All residual lesions can safely receive radiation therapy as assessed by radiation oncologists; 8. Patient can tolerate the radiotherapy process, such as maintaining fixed position; 9. At least one measurable lesion among the oligoresidual lesions according to RECIST v1.1; 10. Agreement to provide archived tumor tissue specimens from primary or metastatic sites, or fresh tissue samples; if unable to provide tumor tissue samples, subjects may be enrolled after investigator assessment if meeting other inclusion/exclusion criteria; 11. Toxicities from previous anti-tumor therapies recovered to ≤ grade 1 per National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE v5.0) (excluding alopecia, fatigue, pigmentation, hypothyroidism stable on hormone replacement therapy, grade 2 peripheral neuropathy after chemotherapy, and exceptions specified in other inclusion criteria); 12. Laboratory values at screening must meet the following criteria: a) Neutrophils ≥ 1.5×10\^9/L b) Platelets ≥ 100×10\^9/L c) Hemoglobin ≥ 90g/L (no blood transfusion within 14 days) d) Serum Cr ≤ 1×ULN, endogenous creatinine clearance \> 50ml/min (Cockcroft-Gault formula) e) AST ≤ 2.5×ULN; ALT ≤ 2.5×ULN; if liver metastases present, ALT and AST ≤ 5×ULN f) Total bilirubin ≤ 1.5×ULN (except for Gilbert's syndrome subjects, where total bilirubin must be \< 51.3μmol/L) g) Thyroid Stimulating Hormone (TSH), Free Triiodothyronine (FT3), Free Thyroxine (FT4) all within ±10% of normal range. Exclusion Criteria: 1. Archived tumor tissue, pre-treatment tumor biopsy, or histological examination showing evidence of previous small cell or mixed small cell/non-small cell histology; 2. Previous tissue samples or peripheral blood genetic sequencing reports indicating EGFR sensitizing mutations, ALK fusion, or other gene variations that should receive standard first-line targeted therapy; squamous cell carcinoma without genetic testing is presumed negative; 3. Symptomatic brain metastases; 4. Leptomeningeal metastases; 5. Active, known, or suspected autoimmune disease (excluding vitiligo, type I diabetes, residual hypothyroidism due to autoimmune thyroiditis requiring only hormone replacement therapy, or conditions not expected to recur in the absence of external triggers); 6. Active tuberculosis (TB) infection as determined by chest X-ray, sputum examination, and clinical examination. Patients with a history of active pulmonary TB infection within the previous year, even if treated, will be excluded. Patients with a history of active pulmonary TB infection more than 1 year ago will also be excluded unless effective previous anti-TB treatment can be documented; 7. Comorbidities requiring immunosuppressive medication, or requiring systemic or local use of corticosteroids at immunosuppressive doses; 8. Pregnancy or breastfeeding; 9. Interstitial lung disease with symptomatic manifestations, or that may interfere with the detection or management of suspected drug-related pulmonary toxicity; 10. Positive for human immunodeficiency virus antibody (HIVAb), active hepatitis B virus infection (HBsAg positive and HBV-DNA \> 10\^3 copies/ml), or hepatitis C virus infection (HCV antibody positive and HCV-RNA \> lower limit of detection at the research center); 11. History of severe neurological or psychiatric disorders, including but not limited to: dementia, depression, seizures, bipolar disorder, etc.; 12. Receipt of other investigational drugs or treatments within 4 weeks prior to study randomization; 13. Use of any Chinese herbal medicines with anti-tumor activity within 2 weeks prior to study drug administration; 14. History of other malignancies (excluding non-melanoma skin cancer and the following in situ cancers: bladder, gastric, colon, endometrial, cervical/dysplasia, melanoma, or breast), unless complete remission was achieved at least 2 years prior to study enrollment and no additional therapy is required or anticipated during the study period; 15. History of severe cardiac or cerebrovascular disease, e.g., New York Heart Association (NYHA) ≥ class 2 heart failure, acute coronary syndrome (such as myocardial infarction, unstable angina, etc.) within 6 months of screening, acute cerebrovascular disease (such as transient ischemic attack, cerebral infarction, cerebral hemorrhage, etc.) within 6 months of screening; 16. Thromboembolic events requiring therapeutic intervention within 6 months prior to screening, such as unstable deep vein thrombosis, arterial thrombosis, and pulmonary embolism; excluding infusion-related thrombosis; 17. Planned vaccination or vaccination with live vaccines within 28 days prior to study randomization; 18. Other conditions deemed unsuitable for participation in this clinical trial by the investigator due to comorbidities or other circumstances.