Primary Tumor Resection With Sintilimab and Chemotherapy in Advanced NSCLC

Inclusion Criteria: 1. Age 18-75 years, no sex limitation; 2. Histologically or cytologically confirmed stage III-IV non-squamous NSCLC, deemed unresectable (evaluated by MDT); 3. Negative for EGFR mutation and ALK rearrangement (tested by ARMS-PCR, NGS, or equivalent methods); 4. No histological evidence of small cell lung cancer (SCLC) or transformation to SCLC; 5. No prior exposure to anti-tumor therapy; 6. ECOG performance status of 0-1; 7. Expected survival ≥ 6 months; 8. Primary tumor diameter ≥ 1 cm, with at least one measurable lesion remaining after resection (per RECIST v1.1 criteria); 9. Adequate major organ function, including: ① Hematologic: absolute neutrophil count ≥ 1.5 × 10⁹/L, platelets ≥ 100 × 10⁹/L, hemoglobin ≥ 9.0 g/dL; ② Hepatic: ALT and AST ≤ 2.5 × ULN (≤ 5 × ULN in case of liver metastases), total bilirubin ≤ 1.5 × ULN; * Renal: serum creatinine ≤ 1.5 × ULN, or creatinine clearance ≥ 50 mL/min (calculated by Cockcroft-Gault formula); 10. Pulmonary function (patients must meet at least one of the following to ensure adequate postoperative pulmonary reserve): ① FEV1 ≥ 1.2 L (or ≥ 40% of predicted value); ② FEV1/FVC ≥ 0.7, excluding severe obstructive ventilatory impairment; ③ DLCO (diffusing capacity for carbon monoxide) ≥ 40% of predicted value, to assess diffusion capacity; ④ If preoperative FEV1 \< 1.2 L or DLCO \< 40%, a quantitative perfusion scan is recommended along with preoperative exercise testing (e.g., 6-minute walk test, stair-climbing test) to evaluate residual pulmonary function; 11. Preoperative assessment by the study team confirming that the patient can tolerate primary lesion resection; 12. Signed informed consent with willingness to comply with study protocol. Exclusion Criteria: 1. Impaired immune function: history of primary immunodeficiency; history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation. 2. Active brain metastases. Patients with adequately treated brain metastases may be eligible if they have remained neurologically stable for at least 2 weeks prior to study entry and are not receiving systemic corticosteroids or are on a stable/reducing dose equivalent to ≤10 mg prednisone daily. 3. Pregnancy. 4. Presence of any severe, uncontrolled, or unstable comorbidity that, in the opinion of the investigator, may interfere with the patient's participation in the study or affect the interpretation of study results, including uncontrolled seizures, psychiatric disorders, active or uncontrolled infections, or other conditions (including laboratory abnormalities).