Future of Japanese Breast Cancer Screening Program Funded by Insurers: Toward ‘Equitable’ Screening Using Ultrasound and Tomosynthesis

Abstract

　For the past 25 years, Japan has followed outdated guidelines for mammography screening, with no proven reduction in breast cancer mortality. This is due to extrapolating Western evidence, which is directly applicable to Japanese women with different breast densities. Japanese women have a higher rate of dense breasts, and the sensitivity of mammography alone for women in their 40s is only 47%. The J-START study, the only RCT (randomized controlled trial) for Japanese women, proves that adding ultrasonography improves sensitivity. Though J-START hasn't shown reduced mortality, it is more relevant than Western RCTs.

　Breast cancer screening funded by insurers should aim to reduce personal mortality risk, promote more early detection and treatment, and prevent workforce loss. It requires more accurate screening methods. Japan lacks an accurate system to track mammography sensitivity and participation rates, contributing to inefficacy. Current guidelines are based on outdated combined mammography and clinical breast examination screening data and do not reflect screening mammography alone data.

　Next-generation breast cancer screening should focus on equitable screening, ensuring all women, especially those with dense breasts, achieve the best outcomes, such as avoiding breast cancer deaths.