Intensive Nutritional Support in Conversion Therapy for Locally Advanced Unresectable ESCC

Inclusion Criteria: Pathologically confirmed Esophageal Squamous Cell Carcinoma (ESCC). Aged 18-80 years, regardless of gender. ECOG Performance Status (PS) 0-2, and weight loss \< 10% within the past 6 months. Confirmed locally advanced unresectable ESCC according to NCCN Guidelines (Version 2026.1). Planned to receive surgery after completion of conversion therapy, with no surgical contraindications. Treatment-naive: No prior anti-tumor therapy for ESCC, including radiotherapy, chemotherapy, or surgery. Presence of measurable lesion(s) according to RECIST 1.1. Expected survival ≥ 3 months. Able to swallow and tolerate oral medications. Adequate organ function (blood counts, biochemistry, and coagulation parameters meeting protocol requirements). Women of childbearing age and men must agree to use effective contraception during the study and for 6 months after completion. Voluntary participation with signed informed consent and good compliance. Exclusion Criteria: Presence of esophageal-mediastinal fistula and/or tracheoesophageal fistula, or tumor invasion of major vessels with risk of fatal hemorrhage. History of other malignant tumors within the past 5 years. Current or prior use of immunosuppressants or systemic steroids (\>10 mg/day prednisone equivalent) within 2 weeks prior to first dose. Active autoimmune disease or history of autoimmune disease requiring systemic treatment. Known immunodeficiency history, including HIV infection, organ transplant, or bone marrow transplant. Uncontrolled concurrent diseases (e.g., uncontrolled hypertension, unstable angina, recent myocardial infarction, or severe infections). Active tuberculosis (TB) or history of TB without standardized treatment. Active Hepatitis B (HBV) or Hepatitis C (HCV) infection. Complete inability to take oral enteral nutrition due to esophageal stenosis. History or current presence of interstitial pneumonia or interstitial lung disease. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring repeated drainage. Significant gastrointestinal disorders with severe diarrhea (CTCAE \> Grade 2). Pregnant or lactating women. Participation in other clinical trials within 30 days prior to enrollment.