This study is a multi-center, non-interventional study. Clinicopathologic, treatment , outcome and efficacy data will be collected from medical records in metastatic esophageal squamous cell carcinoma (ESCC) patients.

This study is a multi-center, non-interventional study. Patients' background, treatment pattern, treatment outcome, efficacy will be collected in metastatic esophageal squamous cell carcinoma (ESCC) patients who were treated with chemotherapy combined with immunotherapy as 1st line treatment at approximately 5 institutions. The patients should have received at least 1 cycle of immunotherapy and chemotherapy with or without radiotherapy. Based on these data, overall survival (OS), progression free survival (PFS) from start of 1st line treatment and the role and efficacy of radiotherapy for these patients will be assessed.

Inclusion Criteria:

1. Pathologically diagnosed as esophageal squamous cell carcinoma;
2. The clinical stage is IVb stage, that is, non-regional lymph node metastasis and distant organ metastasis (AJCC8th) of esophageal carcinoma.
3. Patients had received no previous systemic therapy
4. Patients who had received at least one cycle of first-line chemotherapy combined with immunotherapy, received or did not receive radiotherapy;
5. Complete medical records;
6. ECOG0-2;

Exclusion Criteria:

1. Surgery for esophageal cancer;

2. Esophageal fistulae due to infiltration of the primary tumour.

3. Risk of gastrointestinal bleeding, oesophageal fistula or oesophageal perforation

4. Those who have a history of autoimmune disease or have been treated with immunosuppressants within the last 3 months.

5. Those who have received organ transplant surgery.

6. Patients with a previous history of malignant tumor (skin basal cell carcinoma and cervical carcinoma in situ) survived tumor-free for 3 years after treatment.

   Except for the above).

7. There are other serious diseases, such as myocardial infarction, cerebral infarction or severe cardiopulmonary insufficiency within 6 months

1. The clinical stage is IVb stage, that is, non-regional lymph node metastasis and distant organ metastasis (AJCC8th) of esophageal carcinoma.
2. Patients who had received at least one cycle of first-line chemotherapy combined with immunotherapy, received or did not receive radiotherapy;
3. Pathologically diagnosed as esophageal squamous cell carcinoma;