Chemoembolization, Therapeutic

The goal of this phase 2 trial is to evaluate the efficacy and safety of tislelizumab combined with intravenous chemotherapy and bronchial artery chemoembolization (BACE) as conversion therapy for patients with initially unresectable stage IIIA-IIIB non-small cell lung cancer (NSCLC). The main questions it aims to answer are: * What is the 1-year event-free survival (EFS) rate with this treatment? * Can this treatment improve tumor response and the chance of curative-intent resection? * What adverse events occur during treatment? Participants will receive tislelizumab, intravenous chemotherapy, and BACE for up to 4 cycles. Tumor response and resectability will be evaluated by imaging and multidisciplinary team (MDT) assessment every 2 cycles. Participants who become resectable may undergo surgery followed by postoperative treatment per protocol. Participants who remain unresectable after 4 cycles will receive guideline-recommended chemoradiotherapy followed by tislelizumab consolidation. Regular follow-up will be performed for efficacy and safety assessment.