The integrity of data in a clinical trial is essential, but the current data management process is too complex and highly labor-intensive. As a result, clinical trials are prone to consuming a lot of budget and time, and there is a risk for human-induced error and data falsification. Blockchain technology has the potential to address some of these challenges.The aim of the study was to validate the system, which enables the security of the medical data in clinical trial using blockchain technology.We have developed a blockchain-based data management system for clinical trials and tested the system through a clinical trial for breast cancer. The project was conducted to demonstrate clinical data management using blockchain technology under the regulatory sandbox enabled by the Japanese Cabinet Office.We verified and validated the data in the clinical trial using the validation protocol and tested its resilience to data tampering. The robustness of the system was also proven by survival with zero downtime for clinical data registration during the AWS disruption event in the Tokyo region on August 23, 2019.We show that our system can improve clinical trial data management and could provide trust in the clinical research process and ease for regulators to oversee trials. The system will contribute to the sustainability of healthcare services through the optimization of cost for clinical trials.