Objective Overscreening wastes medical resources, leading to overdiagnosis in cancer screening. In Japan, the national government recommended screening interval for cervical and breast cancer screening is two years, and there are no upper age limits set for cancer screening programs. The participation rate in cancer screening has been lower in Japan than in western countries. It might be affected by the inappropriate use of medical resources, but there are insufficient studies that focus on the utilization of medical resources for cancer screening. Overscreening is estimated based on the national survey for scrutinizing the appropriate utilization of medical resources for cancer screening.

The main reason for overscreening is participation beyond the target age and more frequent screening than the recommended interval. Resource utilization was examined to focus on the efficient use of resources for cervical and breast cancer screening.

Methods Based on the national survey for cancer screening in 2020, the number of cases of overscreening was estimated. This study’s target age was 20-69 years for cervical cancer screening and 40-69 years for breast cancer screening. The subjects were divided into the following groups by age and screening frequency: target age and biennial screening; overage and biennial screening; target age and annual screening; and overage and annual screening. Overscreening included the latter three groups. The percentage of overscreening was compared between cervical cancer and breast cancer screening by a chi-square test.

Results In 2020, the total number of national program participants was 3,109,208 for breast cancer screening and 4,224,543 for cervical cancer screening. The overscreening rate was 39.0% for cervical cancer screening and 38.2% for breast cancer screening. The cause of overscreening was different between cervical and breast cancer screening. Screening at overage was higher in breast cancer screening than in cervical cancer screening (24.6% vs. 16.0%, p<0.01), whereas too-frequent screening, was more elevated in cervical cancer screening than in breast cancer screening (29.3% vs. 19.3%, p<0.01).

Conclusion About 40% is estimated as overscreening for cervical and breast cancer screening, which wastes medical resources for society and harms individual participants. Municipalities that provided a recommended age without an upper age limit are 61.1% for breast cancer screening and 96.5% for cervical cancer screening. In addition, the municipalities provided annually are 28.0% for breast cancer screening and 43.7% for cervical cancer screening. Cancer screening beyond the target age leads to overdiagnosis and unpredictive adverse effects. To avoid these harms, the stopping age should be clarified. There is a misunderstanding that too-frequent screening can save lives through early detection. Education on the appropriate aim of cancer screening is required for local policymakers so that they understand the balance of benefits and harms. Since overscreening is a waste of resources and harms cancer screening, appropriate resource use should be considered as public health policy.