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Accelerated breast MRI for breast cancer screening.
General Poster Session A
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: Current breast MRI protocols are designed for diagnostic, not for screening purposes, and are therefore time consuming to acquire and to read. We investigated whether an abridged breast MRI protocol, consisting only of the first post contrast subtracted (FAST) images and their maximum intensity projection (MIP), would be suitable for screening purposes. Idea was to trade some of the very high sensitivity of breast MRI for acquisition and interpretation speed. Long term goal is to increase the access to breast MRI by reducing the cost associated with the examination. Methods: 443 women at increased risk of breast cancer, with negative digital mammography, underwent 606 breast MRI screening studies. Images were prospectively read by experienced breast radiologists. Readers were asked to first review the MIPs and search for significant enhancement, then to evaluate the FAST images for possible further categorization of enhancement, and only thereafter, to analyse the full diagnostic breast MRI protocol. We compared diagnostic yield and accuracy of MIP and of FAST readings vs. that of the full protocol. Results: MR table time for the full protocol was 21 minutes, table time for FAST images and MIPs was under 3 minutes. Average time to read MIP and FAST image was 2.8 seconds and 28 seconds, respectively. A total 11 breast cancers (4 DCIS, 7 invasive, median size 8 mm, all intermediate or high grade), were diagnosed in the 603 examinations for an additional cancer yield of 18.2/1000. MIPs were positive in 9/11 (82%); FAST readings as well as the full protocol were positive in 10/11 (91%). NPV of the MIP and FAST readings was 99.6% (484/486) and 99.8%, respectively. Specificity of FAST readings was equivalent to that of the full protocol (94.4%), with 33 vs. 35 false-positive diagnoses. Conclusions: In this high risk screening cohort, an MR table time of 3 minutes and an expert radiologist reading time of 2 seconds for the interpretation of the MIP image was sufficient to establish absence of breast cancer with a negative predictive value of 99.6%. With the same abridged MR protocol and an expert reading time of under 30 seconds for interpretation of FAST images, sensitivity and specificity was identical to that of the full protocol, allowing an additional cancer yield of 18.2/1,000.