Rapid MRI of the breast in evaluating lesions discovered on screening

In Canada, breast MRI has traditionally been reserved for evaluation of disease extent in patients with known breast malignancy. More recently, MRI has been emerging as an instrument for breast screening. However, its utilization is limited by increased relative cost and increased reader time. In this study, we evaluate a rapid MRI protocol for breast cancer screening within a breast screening population.

A series of 100 MRI studies performed in a high-risk breast cancer population were selected, ensuring a mix of malignant and benign pathology and normal cases. These were presented as full and abbreviated MRI protocols to 3 breast-trained radiologists. Each case was evaluated for Breast Imaging Reporting and Data Systems (BIRADS) category and the presence or absence of cancer. The time taken to complete and interpret each study was also recorded.

Of the 100 cases, 17 were of histopathology-proven invasive carcinoma, 6 were ductal carcinoma in situ, 33 were benign, and 44 were normal cases. Sensitivity using the rapid protocol was 69.6% (CI: 47.1-86.8) vs 83% (CI: 61.2-95.1) using the full protocol. Specificity using the rapid protocol was 77.9% (CI: 67.0-86.6) vs 83% (CI: 61.2-95.1) using the full protocol. Intra-observer agreement of BIRADS category and cancer detection was very good (0.82-0.93 weighted Kappa and 0.81-0.9 weighted Kappa, respectively). Inter-observer variability of BIRADS category and cancer detection was moderate (0.54-0.59 and 0.53-0.58, respectively).

Our study suggests that a rapid MRI protocol is comparable in performance to that of a standard MRI protocol. In addition, breast imagers are unlikely to change their BIRADS assessment of a study based on the additional sequences provided by the lengthier study. The use of a rapid MRI protocol can improve accessibility, thus making breast MRI a more utilized tool for breast cancer screening.