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 ICIs as 1st line treatment at approximately 26 institutions. The patients should have received at least 1 cycle of anti-PD-1 immunotherapy 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:

Age > 18, had an Eastern Cooperative Oncology Group performance status score of 0-3; Patients had unresectable or recurrent disease that precluded esophagectomy or definitive chemoradiation, or distant metastatic disease; Patients had received no previous systemic therapy (patients who had progressed ≥6 months after [neo]adjuvant therapy or definitive chemoradiation were eligible); Patients accepted at least one cycle of anti-PD-1 immunotherapy as 1st line treatment, combined chemotherapy was allowed.

Patients who provided informed consent by appropriate methods. In dead case, optout will be applicable.

Exclusion Criteria:

Patients who are prior exposure to immune-mediated therapy.

More than 600 patients