Contrast-enhancing foci are normal in healthy premenopausal breasts, even when formal malignancy criteria of enhancement velocity are met. This has to be kept in mind to avoid false-positive results, especially in younger patients.

Background: Breast MRI screening helps detect small, node-negative breast cancers not seen on mammography or ultrasound. Current breast-MRI protocols are designed for diagnostic rather than screening purposes, and are therefore time consuming to acquire and to read, thus limiting access to and availability of screening MRI. We pursued a novel concept for screening MRI by using a protocol that allows a very short acquisition and reading time, and involves expert radiologists to interpret the images. Our screening MRI protocol consists of only the first post-contrast-subtracted (FAST) images and their maximum-intensity-projection (MIP). Purpose: We investigated whether this protocol is suitable for breast-MRI screening of women at slightly to moderately increased risk of breast cancer. Long-term goal is to increase the access to screening breast-MRI. Methods: Prospective IRB-approved observational reader study in 443 women at slightly increased risk of breast-cancer, with normal digital mammograms (n = 606) and ultrasound studies (n = 427), who underwent 606 MRI-screening studies from January 2009 through July 2010, and underwent a 2 year validation period. Expert radiologists reviewed MIP images first to search for significant enhancement, then FAST images to establish a diagnosis. Only thereafter, the regular full diagnostic breast-MRI protocol (FDP) was analyzed. Main outcome measures were Sensitivity, specificity, PPV and NPV, rate of interval cancers and additional cancer yield of MIP/FAST versus FDP readings, and MR table time and time to review MIP and FAST screening MRI Results: MR table time for FDP was 17 minutes vs. 3 minutes for FAST images and their MIP. Average time to read MIP and FAST was 2.8 and 28 seconds, respectively. Eleven breast-cancers (4 DCIS, 7 invasive, all T1N0, all intermediate or high-grade), were diagnosed for an additional cancer yield of 18.2/1000. MIP-readings were positive in 10/11 (90.9%) cancers and yielded a NPV of 99.8% (418/419). FAST and FDP were positive in 11/11 (100%). Specificity and PPV of FAST vs. FDP were equivalent (94.3% vs. 93.9% and 24.4% vs. 23.4%). No interval cancer occurred during the 2 year follow up. Diagnostic Indices of MIP, FAST and Full Diagnostic Protocol MIP*FASTFDPSensitivity90.9%100.0%100.0%Specificityn.a.94.3%93.9%PPVn.a.24.4%23.4%NPV99.8%100.0%100.0%*Since MIP images were used only to rate presence or absence of significant enhancement, the findings cannot be used to calculate specificity and PPV, i.e. indices that communicate the ability to characterize enhancement Conclusion: An MR table-time of 3 minutes and an expert radiologist MIP-image reading time of 3 seconds are sufficient to establish absence of breast-cancer with a NPV of 99.8%. With a reading time of under 30 seconds for FAST, screening MRI is achieved with a diagnostic accuracy equivalent to the full breast-MRI protocol and resulted in an additional cancer yield of 18.2/1000. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-02-14.