3-minute MRI of the Breast for Cancer Screening

Kuhl et al in their JCO article report on the suitability of a fast MRI of breast cancer for screening.  Their protocol consisted of one pre-contrast and one post-contrast sequences their derived images [FAST] and maximum-intensity projection [MIP] images.

They conducted a prospective observational study in 443 women who were at mildly to moderately increased risk for breast cancer who underwent 606 screening MRIs. Eligible women had normal or benign digital mammograms and, for those with heterogeneously dense or extremely dense breasts (n = 427), normal or benign ultrasounds. Breast radiologists with expertise in MRI reviewed the MIP image first to search for significant enhancement and then reviewed the complete study that consisted of MIP and FAST images and optionally their non-subtracted source images and characterized the enhancement in order to establish a diagnosis. Only thereafter was the regular full diagnostic protocol study was analyzed.

MRI acquisition time for complete diagnostic protocol was 17 minutes, versus 3 minutes for the abbreviated protocol (AP). Average time to read the single MIP and complete AP was 2.8 and 28 seconds, respectively. Eleven breast cancers (four ductal carcinomas in situ and seven invasive cancers; all T1N0 intermediate or high grade) were diagnosed, for an additional cancer yield of 18.2 per 1,000. MIP readings were positive in 10 (90.9%) of 11 cancers and allowed establishment of the absence of breast cancer, with a negative predictive value (NPV) of 99.8% (418 of 419). Interpretation of the study using the abbreviated protocol, as with the full diagnostic protocol(FDP), allowed diagnosis of all cancers (11 [100%] of 11). Specificity and positive predictive value (PPV) of AP versus FDP were equivalent (94.3% v 93.9% and 24.4% v 23.4%, respectively).

The authors conclude that the 3 minutes abbreviated protocol and a MIP image are sufficient for an expert radiologist to establish in 3 seconds the absence of breast cancer, with an NPV of 99.8%. With a reading time < 30 seconds for the complete AP, diagnostic accuracy was equivalent to that of the FDP and resulted in an additional cancer yield of 18.2 per 1,000.