mpMRI is based on three types of imaging (anatomic, biological and vascularity). PIRADS uses a 5 point scale based on mpMRI results to assess the probability of the presence of clinically significant prostate cancer. The scale goes from P1 – highly unlikely to have clinically significant cancer to P5 – very likely. PIRADS 5 is defined as a suspicious lesion greater than 1.5 cm, or seminal vesicle invasion, or presence of extra-prostatic extension.
Both versions of the PIRADS are very similar as both are based on evidence and expert consensus, have a 5 point scale for scoring T2 and diffusion-weighted imaging (DWI), and each lesion is given an overall score to indicate chance of being clinically significant prostate cancer.
Major differences in the two versions of the PIRADS include the fact that for version 2, different weighting for peripheral zone (PZ) and transitional zone (TZ) are done, with DWI dominating in PZ and T2 dominating in TZ. Additionally, as opposed to ver. 1, there are simple algorithms and tables to determine overall score in ver. 2.
Dr. Rooij concluded with a summary on the challenges of PIRADS ver. 2, which include:
1. Adaptation of a new system training to reduce inter-observer variability
2. Solving the overlap between BPH and prostate cancer In PIRADS 3 lesion in the TZ
3. Dynamic contrast-enhanced (DCE) is a secondary sequence, upgrade of “3” to “4” based on DCE may create false positives
4. Subjectivity of “hypo-“ and “hyperintense” : there is a clear need for the quantification of DWI
5. Is the cutoff size of 1.5 cm correct?
6. The score does not take into account clinical details
7. There are no guidelines or recommendation for follow-up or biopsy
These challenges must be considered and their solutions must be incorporated into the next version of PIRADS, in a continuing effort to improve utilization of mpMRI in prostate cancer imaging.
Speaker(s): Maarten de Rooij, Nijmegen (NL)
Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto
at the #EAU17 - March 24-28, 2017- London, England