Study to Evaluate the Efficacy and Safety of Adjuvant Tislelizumab in High-Risk Stage I NSCLC

Inclusion Criteria: * Able to provide written informed consent form (ICF) and agree to follow study requirements and assessment schedule. * Aged 18 years or older. * Histologically confirmed stage I non - small cell lung cancer (AJCC 9th edition), with tumor size 2cm \<= T \<=4cm. * Postoperative pathological report shows at least one high-risk factor (visceral pleural invasion, lymphovascular invasion, STAS, poorly differentiated status, high-grade invasive adenocarcinoma (any structure + high grade structure \>=20%, including solid, micropapillary, or complex glands)). * ECOG performance status 0 or 1. * PD-L1 expression \>=1%. * No EGFR/ALK sensitive mutations. * Achieved complete resection (R0) . * Within 8 weeks after surgery, with full recovery from operation. * Adequate organ function. Exclusion Criteria: * Any previous treatment for current lung cancer, including radiotherapy and systemic anti-tumour therapies (chemotherapy, immunotherapy, targeted therapy, anti-angiogenesis therapy, etc.). * Prior chest radiotherapy (including lung, oesophageal, mediastinal, or breast cancer). * Patients with large - cell neuroendocrine carcinoma (LCNEC) or mixed - subtype non - small - cell lung cancer with small - cell components. * With EGFR/ALK sensitive mutations. * Underwent segmentectomy or wedge resection only. * Tumours involving main bronchi, or with obstructive pneumonia/atelectasis (partial or whole lung). * Active autoimmune disease or history of relapsing autoimmune …