Risk of Esophageal Cancer Returning After Immunotherapy, Chemotherapy, and Surgery

This observational study aims to understand the risk of cancer returning after surgery in people with esophageal squamous cell carcinoma, a type of cancer of the food pipe. It focuses on people who received immunotherapy and chemotherapy before surgery. Researchers will review existing medical records, scans, reports on tissue removed during surgery, and follow-up information. They will examine when and where cancer returns and which patient characteristics, treatment details, scan findings, and tissue findings are associated with its return. All treatment and tests were part of routine care. The study does not assign treatment or require additional scans, tissue collection, or follow-up visits.

Inclusion Criteria: * Age 18 years or older at the time of surgery. Histologically confirmed esophageal squamous cell carcinoma. Receipt of neoadjuvant immunochemotherapy, defined as an immune checkpoint inhibitor combined with chemotherapy, followed by curative esophagectomy between August 1, 2020, and October 31, 2025. Microscopically negative surgical margins (R0 resection), postoperative M0 status confirmed on review using the American Joint Committee on Cancer eighth edition staging system, and verifiable postoperative ypT and ypN categories. Availability of FDG PET/CT performed after completion of neoadjuvant treatment and before surgery, together with a verifiable surgery date, recurrence status, and valid follow-up dates. Availability of pretreatment PET/CT is not required. Exclusion Criteria: * Histology other than esophageal squamous cell carcinoma, R1 or R2 resection. Death within 30 days after surgery or absence of any verifiable postoperative outcome follow-up. Missing essential pathological staging information, or survival data that prevent confirmation of eligibility or determination of the primary outcome despite review of source records. Missing nonessential variables alone will not result in exclusion.