Reassessing the public health value of regional cancer registries in the era of Japan's National Cancer Registry: a learning health system perspective.

Cancer registries are integral to public health infrastructure and support not only the monitoring of cancer incidence and mortality but also cancer control planning, quality assurance of screening programs, evaluation of healthcare delivery, prognostic assessment, and development of research infrastructure. Japan's National Cancer Registry (NCR) was launched in 2016, and many long-standing regional cancer registries were subsequently integrated into the national system; however, the Kanagawa Cancer Registry (KCR) continues to operate independently. This Perspective examines how a regional cancer registry can retain public health value in the era of the NCR by serving as infrastructure for a Learning Health System (LHS) that supports cancer screening quality control, regional policy feedback, and continuous improvement. The KCR contributes to screening quality control, projection of cancer care demand, and identification of region-specific challenges that cannot be fully addressed by the NCR alone. In practice, an LHS cycle linking data use, evaluation, feedback, and improvement is gradually being established through the KCR. Thus, regional cancer registries in Japan should be reevaluated not merely as repositories of statistics, but as public health infrastructures that bridge regional policy and clinical practice.