Are Supplemental Screening Ultrasonography and MRI Worthwhile in Women with Excess Risk for Breast Cancer?

The value of adding ultrasonography or magnetic resonance imaging (MRI) to screening mammography remains unknown. Investigators recruited asymptomatic women (median age at enrollment, 55) with dense breasts and at least one additional breast cancer risk factor (e.g., BRCA mutations, histories of breast cancer) to undergo three annual rounds of screening mammography and ultrasound. Tests were considered positive when recommendations were other than routine screening and Breast Imaging-Reporting and Data System (BI-RADS) scores were ≥3. Women were eligible for the MRI substudy if they completed all three rounds of screening and agreed to undergo subsequent contrast-enhanced MRI. A reference standard was defined as the most severe biopsy results (whether cancerous or not) within 1 year of mammographic screening. A total of 2321 women completed the third screen and had reference standards; 612 of these women were included in the MRI analysis.

Overall, 111 primary breast cancers (80% invasive) were diagnosed. Of these, 30% were detected only by mammography, 29% were detected only by ultrasound, 8% were detected only by MRI, and 10% were not detected with any form of imaging. Supplemental ultrasound increased cancer detection by an average of 4.3 cases per 1000 women with each round. Adding MRI further increased cancer detection by an average of 14.7 cases per 1000 women. The number of screens needed to detect one cancer was 127 for mammography, 234 for supplemental ultrasound, and 68 for MRI when mammography and ultrasound screens were both negative. Specificity was reduced with the addition of either ultrasound or MRI.