A Multicenter Prospective Study Evaluating Concurrent Chemoradiotherapy Following Induction Immunochemotherapy for Esophageal Cancer Based on Dynamic ctDNA Monitoring

Inclusion Criteria: * All subjects must sign an informed consent form before initiating any study-related procedures; * All patients must be aged ≥18 years and ≤75 years; * Histologically or cytologically confirmed esophageal cancer (squamous cell carcinoma); * Clinical stage II-IVa, assessed by a surgeon as inoperable, or patient refusal of surgery; * No prior radiotherapy, chemotherapy, immunotherapy, or biotherapy for esophageal cancer; * ECOG performance status of 0-1; * Laboratory test values within the following limits before the first dose of the investigational drug: * Hematology: WBC ≥3.0×10⁹/L; ANC ≥1.5×10⁹/L; PLT ≥70×10⁹/L; HGB ≥9.0 g/dL; * Liver function: AST ≤2.5×ULN; ALT ≤2.5×ULN; * Renal function: Cr ≤1.5×ULN or CrCl ≥40 mL/min; * Coagulation: INR ≤1.5, APTT ≤1.5×ULN; * Other: Lipase ≤1.5×ULN, unless clinically/radiographically insignificant if lipase \>1.5×ULN. Exclusion Criteria: * Insufficient tissue/blood sample available before treatment as required for the study; * Patient refusal to undergo dynamic ctDNA testing; * The primary esophageal lesion is in close proximity to the tracheobronchial tree or major blood vessels, with an investigator-assessed high risk of perforation or major hemorrhage; * History of malignancies other than esophageal carcinoma within the past 5 years (except for curatively treated localized tumors such as carcinoma in situ of the cervix, basal cell carcinoma, or localized prostate cancer); * History of gastrointestinal bleeding within the past 6 months, or coagulopathy at enrollment, or current thrombolytic or anticoagulant therapy indicating a high risk of bleeding; * Severe cardiovascular or cerebrovascular diseases; * History of interstitial lung disease or active pneumonia/tuberculosis; * Severe allergic reactions to paclitaxel/cisplatin or any monoclonal antibody; * Any other condition deemed inappropriate for participation in this study as judged by the investigator.