A Study of Chemoradiation in Combination with Tislelizumab As First Line Treatment in Participants with Advanced Esophageal Squamous Cell Carcinoma

Inclusion Criteria: 1. Subjects must have histologically confirmed squamous cell carcinoma of esophagus (per AJCC 8th edition). 2. Subjects must have unresectable advanced, recurrent or metastatic ESCC. 3. Subjects must not be amenable to curative approaches such as definitive chemoradiation and/or surgery. 4. PD-L1 expression (CPS) is less than 10. 5. No prior systemic anticancer therapy given as primary therapy for advanced or metastatic disease. 6. ECOG Performance Status of 0 or 1. 7. Subjects must have at least one measurable lesion by CT or MRI per RECIST 1.1 criteria; radiographic tumor assessment must be performed within 28 days prior to randomization. 8. Subjects must have adequate organ and bone marrow function. Exclusion Criteria: 1. Presence of tumor cells in the brain or spinal cord which are symptomatic or require treatment. 2. Active known or suspected autoimmune disease. 3. Any serious or uncontrolled medical disorder or active infection. 4. Known history of positive test for human immunodeficiency virus (HIV) or known acquired immunodeficiency syndrome (AIDS). 5. Any positive test result for hepatitis B or C indicating acute or chronic infection and/or detectable virus. 6. Prior treatment with an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or anti-CTLA-4 antibody, or any other antibody or drug specifically targeting T-cell co-stimulation or checkpoint pathways.