Screening ultrasonography revealed 15% of mammographically occult breast cancers

Background Mammography and physical examination (PE) are the recommended modalities for breast-cancer screening for women 40 years and older in Japan. Mammography, however, cannot detect lesions in dense breast tissue, which is common in Japanese women. Breast screening by ultrasound (US) is popular in Japan. We studied which modality or combinations of modalities optimize breast cancer detection for Japanese women. Methods From April 1993 through March 2005 we found 97 breast cancers in 9,082 women by screening examinations with mammography, US, and PE. We compared the detection rates of these three modalities for breast cancer. Results The detection rates of mammography, US, and PE for breast cancer were 83.5 (81 of 97 cancers), 75.3 (73 of 97 cancers), and 60.8% (59 of 97 cancers), respectively. The detection rates of the combinations of mammography and US, mammography and PE, and US and PE were 99.0 (96 of 97 cancers), 88.7 (86 of 97 cancers), and 81.4% (79 of 97 cancers), respectively. Ultrasonography detected 15% of the mammographically occult breast cancers. Conclusion Screening with the combination of mammography and US significantly increases the detection rate of breast cancer. These results suggest that screening with mammography and US would optimize cancer detection in Japanese women.