While the number of newly approved anticancer therapies has increased substantially in the past decade, there remains a need to bring effective treatments to patients more efficiently. In the United States and Europe, real-world data (RWD) are being utilized widely, including in regulatory submissions to assess the potential benefits of therapies in development and address the unmet needs of the patients with limited treatment options. In Japan, given the volume of annual new cancer cases and region-specific circumstances, oncology RWD are crucial for improving patient access to effective therapies. The development of such RWD is underway; a notable recent example is the use of the SCRUM-Japan Registry as a source of external control data in the regulatory approval of pertuzumab and trastuzumab for patients with HER2-positive metastatic colorectal cancer. In addition, electronic health records-based longitudinal, patient-level RWD in Japan are being curated by Flatiron Health K.K. (FHKK), the Japanese subsidiary of Flatiron Health, Inc., by leveraging both structured and unstructured data-processing methodologies developed in the United States over the past decade and tailoring the approach to local requirements. FHKK, in partnership with one of the flagship cancer hospitals in Japan, the National Cancer Center Hospital East (NCCHE), is constructing patient-level RWD in gastrointestinal and other cancers; the first datasets in gastrointestinal cancers will be provided in late 2023. As the curation of oncology RWD in Japan progresses, continuous expansion of the depth and breadth of the data is planned to improve and extend lives of people with cancer.