Introducing the J-CONNECT database: a real-world oncology resource for Japan

Real-world data (RWD) and real-world evidence (RWE) are increasingly important in oncology, where randomized controlled trials often exclude elderly patients, those with comorbidities, and rare cancer subtypes. To meet the need for high-quality oncology RWD in Japan, the J-CONNECT Consortium was launched to build a multiinstitutional database of chemotherapy-treated solid cancer patients using electronic medical records (EMRs).

Data were collected from 12 Ministry of Health, Labour and Welfare-designated cancer care hospitals, with expansion to 15 institutions planned by 2026. J-CONNECT links hospital cancer registry information with EMRs, capturing demographics, staging, treatments, laboratory results, and biomarkers. Coverage and distributional characteristics were evaluated by comparing distributions with the National Hospital-based Cancer Registry by cancer site, age, and sex.

The database included 51,497 patients diagnosed after 2018. Major cancer groups were breast (12,363), lung (6743), prostate (5235), colorectal (4012), pancreas (3720), stomach (2383), esophagus (1960), and liver (1731). Sex distributions were consistent with national data, while some variability was observed by age.

J-CONNECT is a robust oncology database in which clinical and biomarker variables are available, although completeness may vary; fitness-for-purpose should be assessed on a study-by-study basis. Coverage and distributional characteristics and also regulatory acceptance highlight its value for research, PMS, and policy. Future directions include expansion to 25 hospitals, integration of outcome and resource-use data, and adoption of common data models for broader collaboration. We believe J-CONNECT provides valuable oncology data supporting research, post-marketing surveillance, and public health policy in Japan.