Sensitivity and specificity of screening mammography without clinical breast examination among Japanese women aged 40-49 years: analysis of data from the J-START results

Background Current breast cancer screening programs worldwide offer only mammography for asymptomatic women, without clinical breast examination (CBE). The sensitivity and specificity of true asymptomatic screening mammography are important, especially in Japan. Methods This study used data from the Japan Strategic Anti-cancer Randomized Trial (J-START) results, and then calculated the sensitivity and specificity of screening mammography without CBE among Japanese women aged 40-49 years. Results The sensitivity and specificity of modern film mammography, performed biennially, among Japanese women aged 40-49 years were 71.7% and 92.6%, respectively. The sensitivity of mammography alone was 47.4%. From the secondary analysis, the sensitivity of mammography alone was 44.1% for women with dense breasts and 34.8% for women with non-dense breasts. Conclusion The sensitivity of mammography alone of 47.4% is too low. The low sensitivity of screening mammography for true asymptomatic Japanese women aged 40-49 years places this population at an elevated risk, which can justify performing adjunctive ultrasonography.