Surufatinib in Combination With Neoadjuvant Chemo-immunotherapy and Concurrent Chemoradiotherapy for Patients With Unresectable Locally Advanced Esophageal Squamous Cell Carcinoma

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of esophageal squamous cell carcinoma (ESCC). * Locally advanced, unresectable esophageal cancer assessed by endoscopic ultrasound and imaging studies, including esophagography, contrast-enhanced CT scans of the lower neck, chest, and upper abdomen, MRI of the lower neck and chest, whole-body bone scintigraphy, or PET/CT; staged as T2-4, N0-3, M0-1 (M1 limited to supraclavicular lymph node metastasis). * Male or female patients aged 18 to 80 years. * No prior chemotherapy, radiotherapy, surgery, targeted therapy, or immunotherapy. * Expected life expectancy of at least 12 weeks. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Adequate organ and bone marrow function defined as: Forced expiratory volume in one second (FEV1) ≥ 1000 mL; Absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L; Platelet count ≥ 100 × 10⁹/L; Hemoglobin ≥ 90 g/L; Creatinine clearance ≥ 50 mL/min calculated by the Cockcroft-Gault formula (Cockcroft and Gault, 1976); Total bilirubin ≤ 1.5 × upper limit of normal (ULN); Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × ULN. * Signed and dated informed consent form must be obtained prior to any study-related procedures. Exclusion Criteria: * Participation in another clinical trial simultaneously, except for observational (non-interventional) studies. * Prior use of any targeted therapy. * Major surgery within 4 weeks prior to study entry (excluding vascular access procedures). * Uncontrolled comorbidities, including but not limited to active or ongoing infections, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina, arrhythmias, active peptic ulcer disease or gastritis, intestinal perforation, bowel obstruction, active bleeding disorders, or psychiatric/social conditions that may impair compliance with study requirements or the ability to provide informed consent. * Performance status (PS) score of 2-4. * Presence of any of the following organ or bone marrow dysfunctions: Forced expiratory volume in one second (FEV1) \< 1000 mL; Absolute neutrophil count (ANC) \< 1.5 × 10⁹/L; Platelet count \< 100 × 10⁹/L; Hemoglobin \< 90 g/L; Creatinine clearance \< 50 mL/min calculated by the Cockcroft-Gault formula (Cockcroft and Gault, 1976); Total bilirubin \> 1.5 × upper limit of normal (ULN); Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \> 2.5 × ULN. * Any condition that may interfere with the assessment of efficacy or safety of surufatinib.