Ivonescimab Plus Short-Course Hypofractionated Radiotherapy as Second-Line Therapy for Esophageal Squamous Cell Carcinoma

Inclusion Criteria: * a. Patients with histologically confirmed esophageal squamous cell carcinoma (ESCC) , aged 18-80 years; * b. Unresectable locally advanced, postoperative recurrent, or metastatic ESCC that has progressed on or is intolerant to first-line systemic therapy. For patients who received definitive concurrent chemoradiotherapy (CCRT) , disease progression during or within 6 months post-treatment is considered first-line treatment failure; * c. At least one measurable lesion per Response Evaluation Criteria in Solid Tumors (RECIST 1.1) . All positive regional lymph nodes are counted as a single lesion, while non-regional metastatic lymph nodes are counted per station; * d. Adequate major organ function, defined as: 1. Hematology: 1. Hemoglobin (Hb) ≥ 90 g/L 2. White blood cell (WBC) count ≥ 1.5 × 10⁹/L 3. Platelet count ≥ 60 × 10⁹/L 2. Serum biochemistry: 1. Albumin ≥ 25 g/L 2. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × upper limit of normal (ULN) 3. Total bilirubin ≤ 1.5 × ULN 4. Serum creatinine ≤ 1.5 × ULN or creatinine clearance (CrCl) ≥ 60 mL/min 3. Echocardiography: Left ventricular ejection fraction (LVEF) ≥ 50% (lower limit of normal) * e. Eastern Cooperative Oncology Group (ECOG) performance status: 0-2; * f. Expected survival ≥ 3 months; * g. Voluntarily enrolled, with signed informed consent, and willing to comply with study protocols and follow-up. Exclusion Criteria: * a. Patients with severe organ dysfunction, uncontrolled acute infection, or significant comorbidities; * b. Patients with vertebral metastases accompanied by spinal cord compression symptoms; * c. Patients with esophagotracheal or esophagomediastinal fistulas; * d. Patients with uncontrolled pleural, pericardial, or pelvic effusions requiring repeated drainage; * e. Patients with esophageal primary/metastatic lesions invading the heart or great vessels, as assessed by the responsible physician, with a risk of life-threatening hemorrhage; * f. Patients with esophageal primary/metastatic lesions invading the trachea or bronchi, as assessed by the responsible physician, with a risk of esophagotracheal fistula; * g. Patients not suitable for short-course hypofractionated radiotherapy, as evaluated by the responsible physician; * h. Pregnant or lactating women; * i. Patients with mental disorders, or those with a history of psychotropic drug abuse and unable to quit; * j. Patients who have participated in other drug clinical trials within the past 4 weeks; * k. Patients or their families who refuse to participate in the study.