EAU 2018: Prostate Cancer Bi-Parametric Versus Multi-Parametric Magnetic Resonance Imaging
One of the ongoing limitations of mpMRI is that it can take time to image the prostate (>30 min), it can be costly, and the imaging is not always standardized. In recent series, mpMRI has been shown to miss between 2-11% of significant cancers. There are ways, however, that we can improve on these limitations by shaving off potentially unnecessary parts of the test. For example, DCE requires the use of contrast, and contrast uptake by different tissues (such as the brain) has unclear consequences in the long-term. Furthermore, it is somewhat unclear if DCE necessarily improves the detection of significant lesions by experienced radiologists.
DCE is useful for technical DWI failures (such as artificial hip prostheses), can help explain elevated PSAs caused by benign etiologies (prostatitis), and can improve the characterization of PIRADS 3 lesions (lesions can be upgraded to “4” if there is focal vascular enhancement). However, Dr. Barentsz argues that experienced radiologists can differentiate prostatitis from prostate cancer using T2 images, and that the utility of DCE may be overstated.
Bi-parametric MRI (bpMRI) uses only T2 and DWI images, forgoing the need for contrast administration (DCE). Small head-to-head studies comparing bpMRI to mpMRI appears to show that the test characteristics of the two are very similar, detecting similar percentages of high grade lesions with similar negative predictive values. However, bpMRI is most effective in the hands of experienced radiologists.
To further reduce the time commitment needed to obtain an MRI, Dr. Barentsz discussed the possibility of reducing the number of T2 sequences obtained (default is axial, coronal, and sagittal sequences). He showed that it is advisable to maintain at least 2 planes of T2-weighted sequences to insure the ability to properly identify the zone of the lesion and to differentiate “2” from “4” lesions based on location.
In conclusion, a 15-minute bpMRI with two T2-weighted planes may be the optimal test to maximize detection and limit time and costs. However, this technology needs experienced radiologists, and an accreditation process is underway in Europe to make sure radiologists who read these studies are experienced enough to make proper interpretations. Urologists also need to be trained, of course, to make sure they can interpret the images for themselves for surgical planning and for patient counseling.
Presented by: Jelle Barentsz, MD, Nijmegen, The Netherlands
Written by: Shreyas Joshi, MD, Urologic Oncology, Fox Chase Cancer Center, Philadelphia, PA at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark.