Node-Sparing Short-Course Radiotherapy (25 Gy/5 Fractions) Combined With Chemoimmunotherapy as Neoadjuvant Treatment for Locally Advanced Esophageal Squamous Cell Carcinoma：A Prospective Single-Arm, Phase II Study (NeoSCRTIC-01)

Inclusion Criteria:

• Written informed consent before enrollment.
• Age 18 to 75 years, any sex.
• Treatment-naive esophageal squamous cell carcinoma confirmed by pathology and PET-CT.
• Clinical stage cT1b-3N1-2M0 or cT2-3N0M0 (stage II/III according to the AJCC 9th edition).
• Disease assessed as amenable to R0 surgical resection before treatment.
• At least one measurable lesion according to RECIST v1.1.
• ECOG performance status 0-1.
• Adequate organ function: absolute neutrophil count ≥1,500/mm³; platelets ≥100,000/mm³; hemoglobin ≥9 g/dL; serum creatinine ≤1.5 mg/dL and/or creatinine clearance ≥60 mL/min; bilirubin ≤1.5×ULN; AST and ALT ≤1.5×ULN; no blood components or hematopoietic growth factors within 14 days.
• For women of childbearing potential: medically accepted contraception during treatment and for 3 months afterward; negative serum or urine HCG within 7 days before enrollment; not breastfeeding.
• For men who are not surgically sterile: agreement to use medically accepted contraception with their partner during treatment and for 3 months afterward.
• Willingness to participate and comply with safety and survival follow-up.

Exclusion Criteria:

• Prior radiotherapy, chemotherapy, prolonged/high-dose corticosteroid therapy, surgery, or molecular targeted therapy.
• Previous or concurrent other malignancy.
• Prior PD-1/PD-L1 therapy; known allergy to macromolecular protein preparations or any component of PD-1 therapy.
• Active autoimmune disease or relevant autoimmune disease history as specified in the protocol.
• Immunosuppressive agents for immunosuppression within 2 weeks before enrollment.
• Symptomatic pleural or peritoneal effusion requiring therapeutic puncture or drainage.
• Poorly controlled clinically significant cardiac disease as specified in the protocol.
• Abnormal coagulation with bleeding tendency or thrombolytic/anticoagulant therapy.
• Recent gastrointestinal conditions associated with bleeding or perforation risk.
• Severe bleeding within 3 months, hemoptysis within 4 weeks, or thromboembolic event within 12 months according to protocol thresholds.
• Active infection or unexplained fever >38.5°C during screening or before first dose.
• Abdominal fistula, gastrointestinal perforation, or intra-abdominal abscess within 4 weeks before study treatment.
• History/current pulmonary fibrosis, interstitial pneumonia, pneumoconiosis, radiation pneumonitis, drug-related pneumonitis, or severe pulmonary dysfunction.
• Congenital/acquired immunodeficiency including HIV infection, or active hepatitis outside protocol-defined limits.
• Participation in another clinical study or completion of a previous clinical study within 1 month; anticipated need for other systemic anticancer therapy.
• Live vaccine within 4 weeks before study treatment or anticipated during the study.
• Known history of psychotropic drug abuse, alcohol abuse, or illicit drug abuse.
• Unable or unwilling to bear self-paid portions of study-related examinations or treatment.
• Any other condition considered by the investigator to compromise participant safety, study completion, or data/sample collection.