Lymph Node Dissection After Neoadjuvant Therapy for Gastric and EGJ Adenocarcinoma

This multicenter retrospective observational cohort study will evaluate approximately 2,000 adults with gastric or esophagogastric junction adenocarcinoma who received at least two cycles of neoadjuvant therapy followed by R0 gastrectomy with lymph node dissection. The study will estimate the frequency of pathological metastasis at individual lymph node stations according to the final preoperative imaging-based ycT and ycN categories and tumor location. The findings are intended to provide evidence for future prospective studies of risk-adapted reduction of perigastric lymph node dissection. No treatment is assigned by this study.

Inclusion Criteria: * Age 18 years or older. * Histologically confirmed gastric adenocarcinoma or esophagogastric junction adenocarcinoma. * Completion of at least two cycles of neoadjuvant chemotherapy, chemotherapy combined with immunotherapy, or chemoradiotherapy. * Final preoperative imaging assessment within four weeks before surgery with evaluable ycT and ycN categories according to the AJCC/UICC eighth edition. * ycM0 disease before surgery. * R0 curative-intent total, distal, or proximal gastrectomy with lymph node dissection. * Identifiable surgical procedure and evaluable station-specific lymph node pathological records. * Surgery performed between January 1, 2021, and August 30, 2026. Exclusion Criteria: * Histological diagnosis other than adenocarcinoma, including squamous cell carcinoma, lymphoma, gastrointestinal stromal tumor, or neuroendocrine neoplasm. * Conversion therapy for initially unresectable or metastatic disease. * Intraperitoneal hyperthermic perfusion treatment. * ycM1 disease, including peritoneal, hepatic, or other distant metastasis. * R1 or R2 resection, palliative surgery, or exploratory surgery without curative gastrectomy. * Previous gastrectomy. * Synchronous multiple primary gastric cancers. * Another active malignant tumor. * Missing core data required for eligibility or the primary analysis, including ycT, ycN, gastrectomy type, or station-specific pathological records.