An integrated individual patient-level database from JCOG trials in esophageal cancer: A research platform (JCOG2512A).

Randomized controlled trials (RCTs) provide robust evidence in esophageal cancer. Nonetheless, many clinically relevant questions cannot be fully addressed within a single trial. Nationwide registries provide complementary real-world insights but are limited by heterogeneity in patient selection, treatment practices, data quality, data completeness, and follow-up, which constrain the detailed evaluation of time-dependent outcomes and disease-specific endpoints. To address these limitations, the Japan Esophageal Oncology Group of the Japan Clinical Oncology Group established JCOG2512A, an integrated individual patient-level database from prospective interventional trials in esophageal cancer. By harmonizing data collected under standardized eligibility criteria, treatment protocols, and follow-up schedules, this stage-spanning platform enables consistent analyses across disease stages and treatments. Designed as a sustainable research infrastructure that will be continuously updated as new trial results become available, this platform supports clinically meaningful analyses beyond individual RCTs and informs trial design and international collaborative research in esophageal cancer.