The tremendous interest in 3T multiparametric MRI (mpMRI), not only here in the U.S. but around the world, brought with it the challenge of how to standardize the reporting of prostate image analysis among radiologists around the globe. The European Society of Urogenital Radiology (ESUR) proposed a numeric system called the Prostate Imaging Reporting and Data System, or PI-RADS, for prostate cancer detection. It is based in an earlier system for breast imaging, a numeric system called BI-RADS.
Understanding the PI-RADS system in detail is complicated, so let’s try to simplify. We want to help men understand why PI-RADS data are becoming important and what a basic PI-RADS grade might mean with a prostate MRI — which you receive from Diagnostic Imaging Services.
It is becoming quite common for men to be given multiparametric MRI scans as one element in the work-up of a patient who is considered to be at risk for clinically significant prostate cancer, or as a repetitive element in the monitoring of patients who have been diagnosed with prostate cancer but who are being monitored on some form of active surveillance protocol.
Our MRI scan uses techniques that can include a series of factors, such as sequential, high-resolution, T2- or T3-weighted morphological images; diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) images. However, we don’t want men to get too caught up in the technical scan details. What is important is that a standardized system has been developed to give a specific score (on a scale of 1 to 5) to each variable for each lesion that can be seen on the MRI scans.
Rather like a Gleason grade, a score of 1 is considered to be most probably benign and a score of 5 is considered to be highly suspicious of a prostate malignancy.
And, as with Gleason scoring, there are two levels to the system. The first level is the one described above, in which a score is assigned to each image of each lesion. But the second level is one where these scores are added together to provide a total PI-RADS grade and classification for each lesion, as shown below:
PI-RADS (1): Very low: clinically significant cancer is highly unlikely to be present
PI-RADS (2): Low: clinically significant cancer is unlikely to be present
PI-RADS (3): Intermediate: the presence of clinically significant cancer is equivocal
PI-RADS (4): High: clinically significant cancer is likely to be present
PI-RADS (5): Very high: clinically significant cancer is highly likely to be present
If you do have a prostate MRI at DIS as one element in your diagnosis, work-up, or monitoring, you should be asking your doctor if he can tell you your PI-RADS scores for each lesion, because it does certainly give one more way to help to understand your risk, and it does this in a highly standardized manner.
One of the opportunities that is clearly presented by the PI-RADS system is that it may well help physicians to not biopsy men who are at very low risk for clinically significant disease.