Anti-PD-1 Immunotherapy Combined With SBRT for Patients With Oligometastatic ESCC

Inclusion Criteria: 1. Eastern Cooperative Oncology Group performance status ≤ 2; 2. Histologically confirmed squamous cell carcinoma of the esophagus; 3. Diagnosed with stage IVB disease (according to UICC TNM version 8) with less than five metastatic lesions within three organs; 4. Received 4 to 6 cycles of standard chemotherapy (fluoropyrimidine or taxane-based platinum doublet chemotherapy) and anti-PD1 treatment, and no progression disease was confirmed; 5. At least one metastatic lesions amenable to the delivery of SBRT; 6. Estimated life expectancy \>4 months; 7. The function of important organs meet the following requirements: a. white blood cell count (WBC) ≥ 4.0×109/L, absolute neutrophil count (ANC) ≥ 1.5×109/L; b. platelets ≥ 100×109/L; c. hemoglobin ≥ 9g/dL; d. serum albumin ≥ 2.8g/dL; e. total bilirubin ≤ 1.5×ULN, ALT, AST and/or AKP ≤ 2.5×ULN; f. serum creatinine ≤ 1.5×ULN or creatinine clearance rate \>60 mL/min; 8. Ability to understand the study and sign informed consent. Exclusion Criteria: 1. Progression was confirmed after completion of 4 to 6 cycles of standard chemotherapy and anti-PD1 treatment; 2. Patients with intracranial metastasis disease at diagnosis; 3. History of thoracic irradiation; 4. Known or suspected allergy or hypersensitivity to monoclonal antibodies and the chemotherapeutic drugs: Capecitabine, paclitaxel, or platinum; 5. Patients have spinal bone metastases combined with spinal cord compression; 6. A history of malignancies other than esophageal cancer before enrollment, excluding non-melanoma skin cancer, in situ cervical cancer, or cured early prostate cancer; 7. Patients who cannot tolerate radiotherapy due to severe cardiac, lung, liver, or kidney dysfunction, or hematopoietic disease or cachexia; 8. Inability to provide informed consent due to psychological, familial, social, and other factors; 9. Female patients who are pregnant or during lactation; 10. Active autoimmune diseases, a history of autoimmune diseases (including but not limited to these diseases or syndromes, such as colitis, hepatitis, hyperthyroidism), a history of immunodeficiency (including a positive HIV test result), or other acquired or congenital immunodeficiency diseases, a history of organ transplantation or allogeneic bone marrow transplantation; 11. A history of interstitial lung disease or non-infectious pneumonia; Presence of active hepatitis B (HBV DNA ≥ 2000 IU/mL or 104 copies/mL), hepatitis C (positive for hepatitis C antibody, and HCV-RNA levels higher than the lower limit of the assay).