A Study of Tislelizumab (BGB-A317) Plus Chemoradiotherapy Followed by Tislelizumab Monotherapy in Newly Diagnosed, Stage III Subjects With Locally Advanced, Unresectable Non-small Cell Lung Cancer

Inclusion Criteria: 1. Newly diagnosed, histologically confirmed, locally advanced, stage III unresectable non small cell lung cancer (NSCLC). Staging will be confirmed at screening by positron emission tomography-computed tomography (PET/CT) and brain imaging by magnetic resonance imaging (MRI) or computed tomography (CT) with contrast. 2. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1. 3. Epidermal growth factor receptor (EGFR) mutation and anaplastic lymphoma kinase (ALK) gene translocation status available prior to randomization. 4. Provision of fresh or archival tumor tissue or discussion with Sponsor. 5. Adequate hematologic and end-organ function. Exclusion Criteria: 1. Prior therapies including those targeting PD-1 or PD-L1 or chemotherapy, radiation, targeted therapy, biologic therapy, immunotherapy or investigational agent used to control non-small cell lung cancer (NSCLC). 2. History of severe hypersensitivity reactions to other monoclonal antibodies or any contraindication to the planned chemotherapy regimen. 3. History of, or ongoing, interstitial lung disease; pneumonitis requiring steroids; or clinically significant pericardial effusion. 4. Any active malignancy less than or equal to 2 years before randomization, with the exception of non-small cell lung cancer (NSCLC) and any locally recurring cancer that has been treated curatively. 5. Severe chronic or active infections including those requiring systemic antibacterial, antifungal or antiviral therapy; known human immunodeficiency virus (HIV) infection; untreated chronic hepatitis B or chronic hepatitis B virus carries or active hepatitis C; or active autoimmune disease. 6. Prior allogeneic stem cell transplantation or organ transplantation. 7. Significant cardiovascular disease or other condition which places the patient at risk.