Serplulimab Monotherapy in Elderly Patients With NSCLC and PD-L1 TPS ≥ 50%

Inclusion Criteria: * 1.Voluntary participation and informed consent: Subjects must voluntarily join the study, sign the written informed consent form (ICF), and demonstrate good compliance. 2.Age and Gender: Aged ≥65 years at the time of signing the ICF, regardless of gender. 3.Diagnosis and Staging: Histologically or cytologically confirmed Stage IIIB (ineligible for definitive chemoradiotherapy), Stage IIIC, or Stage IV NSCLC according to the AJCC 8th edition staging system. 4.PD-L1 Expression: Tumor tissue confirmed as PD-L1 TPS≥50% by a central laboratory or a validated local laboratory, using SP263 or 22C3 assays (a formal test report must be provided). 5.Driver Gene Status: Known absence of actionable driver mutations, including but not limited to EGFR sensitive mutations, ALK fusions, and ROS1 fusions. 6.Measurable Disease: At least one measurable target lesion per RECIST v1.1 criteria (lesions must not have received prior radiotherapy). 7.Prior Treatment History: No prior systemic therapy for advanced or metastatic disease. For patients who received adjuvant or neoadjuvant chemotherapy, inclusion is permitted if disease recurrence occurred ≥6 months after the completion of the last dose. 8.Performance Status: Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0-2. 9.Adequate organ and bone marrow function (no blood transfusions or hematopoietic stimulating factor therapy within 14 days prior to the first dose): * Absolute Neutrophil Count (ANC)≥1.5 x 10\^9//L * Platelet Count (PLT)≥100 x 10\^9//L * Hemoglobin (Hb)≥90 g/L * Serum Creatinine (Cr) ≤ 1.5 x Limit of Normal (ULN) or Creatinine Clearance ≥ 50mL/min * Total Bilirubin (TBIL) ≤ 1.5 x ULN * Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT)≤ 2.5 x ULN(≤ 5 x ULN for patients with liver metastases) Exclusion Criteria: * 1\. Hypersensitivity: Known hypersensitivity to serplulimab or any of its excipients. 2\. Prior Immunotherapy: Prior treatment with any anti-PD-1, anti-PD-L1, anti-CTLA-4, or other immune checkpoint inhibitors (ICIs). 3\. Autoimmune Disease: Active autoimmune disease requiring systemic treatment (e.g., corticosteroids or immunosuppressants) within the past 2 years. Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid replacement for adrenal or pituitary insufficiency) is permitted. 4\. Lung Disease/Pneumonitis: Active interstitial lung disease (ILD) or pneumonitis, or a history of (non-infectious) pneumonitis requiring steroid treatment. 5\. Infections: Active infection requiring systemic therapy. 6. CNS Metastases: Known active central nervous system (CNS) metastases and/or carcinomatous meningitis. However, patients with treated (via surgery or radiotherapy) and stable brain metastases are eligible, provided they are radiographically stable for at least 4 weeks prior to the first dose, have no evidence of new or enlarged brain lesions, and have discontinued glucocorticoids for at least 14 days. 7\. Pregnancy and Breastfeeding: Pregnant or breastfeeding women. 8. Investigator Discretion: Any other condition that, in the investigator's opinion, may interfere with the evaluation of the study drug, jeopardize subject safety, or confound the interpretation of study results.