Radiotherapy Plus Anti-PD-1 Versus Anti-PD-1 Alone in ypTanyN⁺M0 NSCLC

Inclusion Criteria: * Age 18-75 years, male or female. * Histologically confirmed NSCLC (adenocarcinoma, squamous cell carcinoma, or other NSCLC subtypes). * Clinical stage IIIA/IIIB at initial diagnosis, deemed suitable for neoadjuvant chemoimmunotherapy followed by surgery according to MDT. * Completed 2-4 cycles of platinum-based doublet chemotherapy plus PD-1 inhibitor as neoadjuvant therapy. * Underwent R0 resection (anatomical lobectomy or pneumonectomy with mediastinal lymph node dissection). * Postoperative pathological stage ypT\_anyN⁺M0 (residual nodal metastasis in mediastinal or hilar lymph nodes). * ECOG performance status 0-1. * Adequate hematologic, hepatic, and renal function per protocol-defined lab thresholds. * Able to start postoperative radiotherapy and/or PD-1 maintenance within 4-10 weeks after surgery (or after recovery from postoperative complications, as clinically appropriate). * Signed written informed consent. Exclusion Criteria: * Positive surgical margins (R1 or R2) or incomplete resection. * Prior thoracic radiotherapy that would overlap with planned treatment fields. * Active, uncontrolled infection or unresolved ≥ Grade 2 immune-related adverse events. * History of severe autoimmune disease requiring systemic immunosuppression. * Uncontrolled interstitial lung disease or significant pulmonary fibrosis. * Symptomatic or untreated central nervous system metastases at enrollment. * Any condition that, in the investigator's judgment, would compromise patient safety or protocol compliance.