Does MRI Offer Any Advantage Over Breast Tomography with Ultrasound when Screening for Breast Cancer?
Breast MRI is an accepted screening modality in genetically high-risk women and those whose calculated risk is high, as well as in women with dense breast tissue. However, many women object to routine screening with MRI due to claustrophobia and/or the intravenous injection of gadolinium. Despite no evidence of clinical harm, some are concerned about the unknown effects of possible gadolinium deposits in the brain. In comparison, Digital Breast Tomosynthesis (DBT) requires no intravenous contrast, has faster image acquisition, and there is no associated claustrophobia. Questions have arisen as to its sensitivity and specificity compared to breast MRI and two studies examine this question.
In the Bosnian Journal of Basic Medical Sciences, Roganovic et al. from Bosnia and Herzegovina reviewed 57 symptomatic and asymptomatic women referred to their breast imaging center. All had standard digital mammography (DM), DBT and MRI. Both DBT (p=0.001) and MRI (p=0.02) outperformed standard DM.
The sensitivity of DM was 72.4%, and specificity, 46.4% whereas the sensitivity of DBT was 100% and specificity 75%. The sensitivity and specificity of MRI was 93.1% and 60.7% respectively (ROC curves below).
The authors concluded that there was a significant difference in performance between DM and DBT as well as between DM and MRI. There was no statistical difference between MRI and DBT (p=0.07). The study was limited by small sample size and non-blinded review.
The second study by Mariscotti et al. was performed in Italy prospectively on 200 consecutive women with histologically proven breast cancer. All patients underwent DM incorporated with DBT as well as ultrasound and MRI. There was no difference between MRI alone and the combination of DM with DBT (p=1.0). While breast density did not impact MRI sensitivity, ultrasound sensitivity was higher in the dense breast. Sensitivity of both DM and DBT was higher in the non-dense breast.
MRI and ultrasound had the highest sensitivity in identifying multicentric and multifocal disease, although they offered only a slight difference compared to DBT (p=0.049). The modality with the highest sensitivity in identifying synchronous bilateral cancer was MRI, followed by DBT.
The authors concluded “that there was little to no gain in sensitivity and no gain in overall accuracy by performing MRI in women who have been evaluated previously by DM, DBT, and ultrasound”. They noted that “further addition of MRI to conventional imaging with DBT did not statistically contribute to detection yield.”
These screening studies are small; yet enough issues surround MRI to consider another prospective randomized study of sufficient size be performed to answer the following questions: In light of advances with DBT plus ultrasound where does MRI fit in the armamentarium of breast imaging? Is MRI appropriate only for screening in those at ultrahigh risk (e. g. BRCA)? Is MRI superior to DBT plus ultrasound in evaluating multicentric disease or extent of disease? These reported advances with DBT suggest that it is time to reset the role of breast MRI.