A Study to Investigate Tislelizumab (BGB-A317) Versus Placebo in Combination With Concurrent Chemoradiotherapy in Participants With Localized Esophageal Squamous Cell Carcinoma

Key Inclusion Criteria: * Histologically confirmed diagnosis of localized ESCC and suitable for concurrent chemoradiotherapy (cCRT) * Measurable and/or non-measurable disease defined per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 * Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1 * Adequate organ function Key Exclusion Criteria: * Indicators of severe malnutrition * Clinically uncontrolled pleural effusion, pericardial effusion, or ascites requiring frequent drainage or medical intervention within 2 weeks prior to randomization * Known to be intolerable or resistant to treatment with the protocol-specified chemotherapy * Received prior radiotherapy or therapies targeting programmed cell death protein-1 (PD-1), programmed cell death protein ligand-1 (PD-L1), PD-L2 or other immune-oncology therapies * Active autoimmune diseases or history of autoimmune diseases that may relapse NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.