Helicobacter Pylori Infection Status and Pathological Features for Predicting Gastric Cancer Biological Behavior and Prognosis: A Real-World Observational Study

Inclusion Criteria:

* Adults aged 18 to 80 years
* Retrospectively identified or prospectively enrolled patients with early gastric cancer, high-grade intraepithelial neoplasia, or other gastric neoplastic lesions treated with or scheduled for endoscopic submucosal dissection according to standard clinical indications at participating medical centers
* Availability or planned availability of sufficient Helicobacter pylori assessment data for study classification, including 13C-urea breath test, serum Helicobacter pylori IgG antibody testing, pathological assessment of gastric tissue, prior H. pylori infection history, prior eradication history, eradication confirmation, or follow-up H. pylori testing results when available
* Availability or planned availability of gastric tissue pathological assessment from routine biopsy specimens and/or endoscopic submucosal dissection specimens for evaluation of tissue-based H. pylori detection, background mucosal changes, lesion pathological characteristics, and ESD-related pathological findings
* Availability or planned availability of key clinical, endoscopic, and pathological information required to evaluate gastric cancer subtype, biological behavior, and curability after ESD, including lesion location, histological subtype, differentiation, depth of invasion, lymphovascular invasion, margin status, curative resection status, and additional treatment information when available
* Availability of follow-up data for retrospectively included participants, or willingness and ability to participate in follow-up evaluations for prospectively enrolled participants, including endoscopic follow-up at approximately 1, 2, and 3 years after ESD and longer-term follow-up when available
* Adequate cardiac, hepatic, renal, and pulmonary function to tolerate endoscopic treatment and routine follow-up for prospectively enrolled participants scheduled for ESD
* Ability to provide written informed consent for prospectively enrolled participants, or availability of ethics-approved retrospective clinical data for retrospectively included participants

Exclusion Criteria:

* Patients whose final diagnosis does not meet the study population definition, including those without early gastric cancer, high-grade intraepithelial neoplasia, or other eligible gastric neoplastic lesions
* Insufficient clinical, H. pylori testing, endoscopic, pathological, or follow-up information to classify H. pylori infection or eradication status or to evaluate the main study outcomes
* Lack of adequate pathological material or pathological information for assessment of gastric lesion characteristics, tissue-based H. pylori detection, or background mucosal changes
* Previous gastrectomy or major gastric surgery that substantially alters gastric anatomy and prevents reliable assessment of lesion location, intragastric distribution, or background mucosal status
* For prospectively enrolled participants scheduled for ESD, severe comorbid conditions, such as uncontrolled cardiovascular or cerebrovascular disease, severe coagulopathy, or very poor general condition, that make endoscopic submucosal dissection unsafe
* For prospectively enrolled participants scheduled for ESD, anticoagulant or antiplatelet therapy that cannot be safely interrupted or managed during the perioperative period, or active bleeding tendency judged to significantly increase procedural risk
* Pregnancy or breastfeeding for prospectively enrolled participants
* Inability or unwillingness to comply with study procedures or follow-up requirements for prospectively enrolled participants
* Any other condition judged by the investigators to make the participant unsuitable for the study