8609 Background: Bronchial artery chemoembolization (BACE) and immune checkpoint inhibitors (ICIs) are important therapy for NSCLC. The short-term benefit from BACE is considerable while the long-term survival benefits from ICIs is remarkable. This trial is designed to determine the efficacy and safety of immunotherapy with tislelizumab in addition to BACE in stage III-Ⅳ NSCLC patients (pts) who failed, refused or ineligible to receive standard treatments. Methods: In a single-arm, phase II study (NCT05058560), stage III-IV NSCLC patients who refused or were ineligible to receive standard treatments were enrolled. Patients received BACE followed by 200 mg tislelizumab every 3 weeks until disease progression, intolerable toxicities, or discontinuation determined by the investigators. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR), safety, and quality of life (QoL). Results: Thirty patients were enrolled in this study between December 2021 and August 2022. The median follow-up was 12 (range, 1.5-12) months. At the data cutoff (August 31, 2023), the median PFS was 10.5 (95% confidence interval [CI], 7.8-13.2) months and the median OS was not reached. The 3 -, 6 -, and 12-month ORR were 63.3% (95%CI, 43.9%-80.1%), 56.7% (95%CI, 37.4%-74.5%), and 30.4% (95%CI, 13.2%-52.9%), respectively. The DCR at 3 months was 80% (95%CI, 61.4%-92.3%), at 6 months was 76.7% (95%CI, 57.7%-90.1%), and at 12 months was 47.8% (95%CI, 26.8%-69.4%). The expression rate of PD-L1, tumor feeding arteries, and the application times of tislelizumab were prognostic factors for PFS. No grade 3 or higher treatment-related adverse events (TRAEs) occurred. Common grade 2 TRAEs were nausea, fever, and cough. QoL improved significantly after 1 cycle of treatment compared with baseline, including global quality of life, physical functioning, and emotional functioning. Conclusions: The study demonstrated promising efficacy and manageable safety profiles of BACE plus tislelizumab for advanced NSCLC patients, indicating a potential and effective treatment option for this population. Clinical trial information: NCT05058560 .