PD-1 Inhibitor Plus Chemotherapy With or Without Radiotherapy in Patients With Metastatic Esophageal Cancer

Inclusion Criteria: * 1\. ≥18 years, any gender * 2\. Histologically or cytologically confirmed squamous cell carcinoma of esophageal cancer. The initial clinical stage is IVb (2018 American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 8th Edition) , with distant metastasis involving no more than 2 organs (lymph node metastasis is counted); * 3\. ECOG (Eastern Cooperative Oncology Groupper) formance status \<= 1. Patients aged 65 years and over need to complete G8 screening or Comprehensive Geriatric Assessment, and the final evaluation is good; * 4.There was no significant abnormality in laboratory routine indicators such as blood routine and liver and kidney function; * 5.No prior history of thoracic radiation; * 6.Expected survival is more than 12 weeks; * 7.Informed consent provided. Exclusion Criteria: * 1.Patients with other cancer history except hypopharyngeal carcinoma in situ, non-malignant skin cancer and cervical carcinoma in situ. * 2.Received surgery (except ostomy), chemotherapy or other anti-tumor treatment before enrollment； * 3\. Active infection currently exists . The following conditions occurred within 6 months before randomization: myocardial infarction, cerebrovascular accident, or received gastrointestinal, neurological, cardiopulmonary surgery; * 4\. History of allergy to chemotherapy drugs or autoimmune disease; * 5\. Participate in other clinical trials at present or within 4 weeks before enrollment; * 6.There are factors such as high risk of fistula that radiotherapy cannot be safely carried out as assessed by the radiation oncologist.