A Randomized, Placebo-Controlled, Double-Blind Phase 3 Study to Evaluate the Efficacy and Safety of Tislelizumab (BGB-A317) in Combination With Chemotherapy as First-Line Treatment in Patients With Unresectable, Locally Advanced Recurrent or Metastatic Esophageal Squamous Cell Carcinoma

Experimental: Tislelizumab + Chemotherapy

Tislelizumab 200 milligrams (mg) administered intravenously (IV) on Day 1 of each cycle every 3 weeks (Q3W) plus one of the following until unacceptable toxicity, disease progression or withdrawal for other reasons; each cycle is 21 days~* Chemotherapy Doublet A: cisplatin 60-80 mg/m\^2 or oxaliplatin 130 mg/m\^2 administered IV on Day 1 of each cycle Q3W and 5-fluorouracil IV 750-800 mg/m\^2 on Days 1 to 5 of each cycle Q3W;~* Chemotherapy Doublet B: cisplatin 60-80 mg/m\^2 or oxaliplatin 130 mg/m\^2 administered IV on Day 1 of each cycle Q3W and capecitabine orally 1000 mg/m\^2 on Days 1 to 14 of each cycle, twice a day; or~* Chemotherapy Doublet C: cisplatin 60-80 mg/m\^2 administered IV on Day 1 or 2 or oxaliplatin 130 mg/m\^2 administered IV on Day 1 of each cycle Q3W and paclitaxel 175 mg/m\^2 IV on Day 1 of each cycle Q3W; cisplatin may be given in 3 divided doses on Days 1, 2, and 3 depending on local guidelines

Active_comparator: Placebo + Chemotherapy

Matched placebo administered IV on Day 1 of each cycle every 3 weeks (Q3W) plus one of the following until unacceptable toxicity, disease progression or withdrawal for other reasons; each cycle is 21 days~* Chemotherapy Doublet A: cisplatin 60-80 mg/m\^2 or oxaliplatin 130 mg/m\^2 administered IV on Day 1 of each cycle Q3W and 5-fluorouracil IV 750-800 mg/m\^2 on Days 1 to 5 of each cycle Q3W;~* Chemotherapy Doublet B: cisplatin 60-80 mg/m\^2 or oxaliplatin 130 mg/m\^2 administered IV on Day 1 of each cycle Q3W and capecitabine orally 1000 mg/m\^2 on Days 1 to 14 of each cycle, twice a day; or~Chemotherapy Doublet C: cisplatin 60-80 mg/m\^2 administered IV on Day 1 or 2 or oxaliplatin 130 mg/m\^2 administered IV on Day 1 of each cycle Q3W and paclitaxel 175 mg/m\^2 IV on Day 1 of each cycle Q3W; cisplatin may be given in 3 divided doses on Days 1, 2, and 3 depending on local guidelines