Induction Immuno-chemotherapy and Concurrent Chemoradiotherapy With or Without Apatinib in Unresectable, Locally Advanced Esophageal Squamous Cell Carcinoma

Inclusion Criteria: * Diagnosed with esophageal squamous cell carcinoma through pathological examination or cytological examination; * Evaluated as locally advanced esophageal cancer that is unresectable through endoscopic ultrasound, imaging studies including barium swallow, CT scans of the neck, chest, and upper abdomen, MR imaging of the neck and chest, whole-body bone scan, or PET/CT, with staging ranging from T2-4, N0-3, M0-1 (M1 only includes patients with supraclavicular lymph node metastasis); * Male or female aged between 18 and 80 years old; * No prior chemotherapy, radiotherapy, surgery, targeted therapy, or immunotherapy; * Expected survival of ≥12 weeks; * ECOG performance status score of 0 or 1; * Organ and bone marrow function meeting the following criteria: forced expiratory volume in 1 second (FEV1) ≥800 ml; absolute neutrophil count ≥1.5×109/L; platelet count ≥100×109/L; hemoglobin ≥90 g/L; serum creatinine clearance calculated according to the Cockcroft-Gault formula ≥50 mL/min (Cockcroft and Gault 1976); serum bilirubin ≤1.5 times the upper limit of normal (ULN); aspartate aminotransferase and alanine aminotransferase ≤2.5 times ULN; * Signed and dated informed consent form is required before any study procedures are performed. Exclusion Criteria: * Participating in another clinical study concurrently, unless it is an observational (non-interventional) clinical study; * Prior use of any targeted therapy or immunotherapy; * Underwent major surgery (exclu…