Low-Dose Involved-Field Radiotherapy Plus Immunochemotherapy for ESCC

Inclusion Criteria: * Age 18-80 years * Patients with locally advanced, unresectable ESCC who have received radical treatment (radical chemoradiotherapy or radical radiochemotherapy), including: Cervical esophagus involvement, T4 stage, supraclavicular lymph node metastasis, or inability to tolerate or refusal of surgery due to personal reasons; Failure of neoadjuvant or conversion therapy;Unresectable local recurrence after surgery (with measurable target lesions) * No evidence of tumor recurrence or metastasis on follow-up examination 2-3 weeks after radical treatment * Ability to provide fresh tumor tissue specimens (baseline) * Normal function of major organs * Performance Status (PS) score ≤ 1 * Patients of childbearing potential must agree to use contraception. * Voluntary participation with signed informed consent Exclusion Criteria: * History of fistula formation due to primary tumor invasion * High risk of gastrointestinal bleeding, esophageal fistula, or esophageal perforation. * Poor nutritional status * Previous immune-related adverse events during prior radical treatment, including grade ≥3 immune-related pneumonitis, myocarditis, etc * Presence of symptoms or signs of interstitial disease * Patients with any severe and/or uncontrolled medical condition * Presence of concurrent malignancies * Presence of other autoimmune diseases or long-term use of immunosuppressants or corticosteroids. * Patients who are difficult to communicate with or are unlikely to comply with long-term follow-up. * Any other conditions that the investigator deems unsuitable for participation.