This prospective, multi-center, observational registry study (PKU-ESCC-EF) aims to evaluate the safety and effectiveness of a standardized diagnosis and treatment protocol for esophageal fistula (EF) in patients with advanced esophageal squamous cell carcinoma (ESCC). Esophageal fistula is a severe complication that often leads to life-threatening infections and poor nutrition. This study will observe patients receiving a comprehensive management strategy, which includes fistula sealing with esophageal or airway stents, targeted anti-infective therapy, nutritional support, and subsequent systemic anti-tumor therapy. The primary goal is to assess whether this standardized approach can improve overall survival and enable more patients to receive further anti-cancer treatments.

This observational registry employs a prospective, single-arm design to recruit eligible patients with newly diagnosed esophageal fistula (tracheoesophageal or mediastinal fistula) complicating unresectable advanced esophageal squamous cell carcinoma. All enrolled participants will receive management according to a predefined standardized diagnostic and therapeutic protocol. The protocol integrates a comprehensive workflow from diagnostic assessment to multidisciplinary intervention: initial diagnosis is supported by clinical manifestations, imaging studies, and endoscopic evaluation, followed by interventional fistula closure using esophageal or airway covered stents selected according to fistula characteristics. Accompanying medical support includes anti-infective therapy, negative pressure suction, anti-reflux treatment, and nutritional support. After achieving adequate fistula control and clinical stabilization, subsequent systemic anti-tumor therapy may be administered based on investigator assessment. Prospective data collection will encompass fistula sealing status, nutritional parameters, quality of life, subsequent anti-tumor treatment rate, overall survival, and exploratory biomarker analysis of biospecimens, thereby providing real-world evidence to standardize management strategies for this serious complication.

Inclusion Criteria:

• Voluntary participation and provision of written informed consent.
• Age between 18 and 75 years (inclusive).
• Histologically confirmed diagnosis of esophageal squamous cell carcinoma.
• Radiologically confirmed unresectable, advanced disease.
• Newly diagnosed esophageal fistula (including tracheoesophageal fistula or mediastinal esophageal fistula).
• Previous receipt of ≤ 3 lines of systemic anti-tumor therapy.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Adequate organ and marrow function within 7 days prior to potential anti-tumor treatment, as defined by:
• Hemoglobin ≥ 9.0 g/dL
• Absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L
• Platelet count ≥ 100 × 10⁹/L
• Total bilirubin (TBIL) ≤ 1.5 × the upper limit of normal (ULN)
• Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × ULN (or ≤ 5 × ULN in the presence of liver metastases)
• Serum creatinine ≤ 1.5 × ULN
• Adequate cardiac, pulmonary, and renal function to be eligible for general anesthesia, with no contraindications to general anesthesia.

Exclusion Criteria:

• Patients with postoperative anastomotic fistula.
• Uncontrolled active bleeding.
• Presence of a concurrent primary malignancy other than esophageal carcinoma.
• Clinically significant cardiovascular disease, including but not limited to:
• Heart failure (NYHA Class III-IV)
• Uncontrolled coronary artery disease, cardiomyopathy, or arrhythmia
• Uncontrolled hypertension
• History of myocardial infarction within the past 1 year
• Neurological or psychiatric disorders that impair cognitive ability, including the presence of central nervous system metastases.
• Uncontrolled, active severe clinical infection ( > Grade 2 per NCI-CTCAE version 5.0) within 14 days prior to enrollment, including active tuberculosis (this is a contraindication for anti-tumor therapy, not for interventional procedures).
• Known or self-reported HIV infection, or active Hepatitis B or Hepatitis C.
• A history of interstitial lung disease (e.g., interstitial pneumonia, pulmonary fibrosis), or evidence of interstitial lung disease on baseline chest X-ray/CT.

The study population will consist of adult patients (aged 18-75 years) with unresectable, advanced esophageal squamous cell carcinoma (ESCC) who have been newly diagnosed with an esophageal fistula (tracheoesophageal or tracheomediastinal fistula). Eligible participants must have received no more than three prior lines of systemic anti-tumor therapy and must demonstrate adequate organ function and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2, making them potential candidates for subsequent anti-tumor treatment following fistula management. Patients with postoperative anastomotic leaks, other active malignancies, uncontrolled infections, significant cardiopulmonary disease, or other specified exclusion criteria will not be eligible for enrollment.