Cancer screening programs in Japan: Progress and challenges.

National screening programs for gastric, colorectal, lung, breast, and cervical cancers are offered in Japan. The initial introduction of cancer screening programs was decided based on experts' opinions. Since 2003, the research groups funded by the National Cancer Center have published screening guidelines for gastric, colorectal, lung, prostate, cervical, and breast cancers. Although such guidelines have increasingly contributed to promoting evidence-based screening, it is still insufficient. Cancer screenings have mainly been provided in communities and workplaces. Compared with the average of OECD countries, participation rates in breast and cervical cancer screening are lower. Participation rates cannot be accurately calculated due to a lack of comprehensive cancer screening registries at the national level. Alternatively, estimates are derived from questionnaire surveys conducted on randomly selected samples from the national population. The quality assurance system has been limited to community-based screening and was not adapted to workplace screening until 2018. While there is a long history of cancer screening, the complex program delivery system might be a barrier to increasing the participation rate. Continued efforts are necessary to offer evidence-based cancer screening and establish an effective quality assurance system.