Two arms adopt local intervention administered at distinct timings.

Although immunotherapy combined with chemotherapy has become the first-line standard regimen for advanced esophageal squamous cell carcinoma (ESCC) and improved clinical outcomes in advanced patients, the prognosis of patients with esophageal cancer remains unsatisfactory, with a 5-year overall survival rate below 20%. As an effective modality for local disease control, local radiotherapy has no established optimal sequencing schedule when combined with systemic therapy. The timing of radiotherapy intervention may directly affect treatment efficacy, treatment tolerance and quality of life of patients. Several studies have explored the impact of radiotherapy timing in oligometastatic ESCC, yet substantial limitations persist in current evidence, resulting in a lack of unified guideline recommendations and wide heterogeneity in clinical practice. Most existing investigations are retrospective or small-sample prospective studies with high heterogeneity in study design, patient population selection and treatment regimens, yielding inconsistent conclusions that cannot support consistent clinical consensus. To clarify the impact of radiotherapy timing on clinical efficacy in oligometastatic esophageal cancer, the investigator designed the present clinical trial. This study aims to compare the efficacy and safety of concurrent radiotherapy versus sequential radiotherapy on the basis of immunochemotherapy among patients with oligometastatic ESCC, so as to fill the evidence gap in existing research.