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EAU PCa 2018: When to Use MRI in the Diagnosis of Prostate Cancer?

Milan, Italy (UroToday.com) Dr. Villeirs gave an update on the usage of MRI in the diagnosis of prostate cancer. He began his discussion on the scoring system of prostate MRI:  The Prostate Imaging Reporting and Data System (PIRADS), defining standards of high-quality clinical service for multi-parametric Magnetic Resonance Imaging (mpMRI), including image creation and reporting. The PIRADS has been validated in a meta-analysis of 21 studies including over 3857 patients. This demonstrated a pooled sensitivity of 89% and a pooled specificity of 73%.1 These results were irrespective of the magnet strength (1.5 T or 3.0 T). Additionally, there have been multiple single-institution studies demonstrating fair sensitivity for detection of any cancer, and high sensitivity (90%) for the detection of clinically significant cancer (Gleason Grade group 3-5). Furthermore, these data demonstrate a high negative predictive value (90%) for the exclusion of clinically significant cancer (Gleason grade group 3-5).

In a study evaluating the histologic significance of every level of the PIRADS scoring system2, the correlation of the PIRADS scoring system to the Gleason Grade group was quite high (Figure 1).

Figure 1: Correlation of mpMRI PIRADS 2 results and Gleason Grade Groups:
UroToday EAUPCa18 Correlation of mpMRI PIRADS 2 results and Gleason Grade Groups

These results demonstrate that there is a clear rationale for mpMRI. If it is negative with no suspected lesions, there is no need to do a biopsy, as it has a high negative predictive value for excluding clinically significant disease. If the mpMRI is positive, a targeted biopsy is required for the visible mpMRI lesion. mpMRI targeted biopsies can be performed in three ways: 1. Cognitive, 2. MRI-US fusion, 3. MRI in bore. A study published in 2017 had demonstrated no difference in results between these three techniques3. 

The European Association of Urology (EAU) guidelines state the mpMRI should only be performed in the setting of repeat biopsy when clinical suspicion of prostate cancer persists despite negative biopsies. The guidelines also state that systematic biopsies should always be performed in addition to the targeted biopsies. The relative sensitivity of mpMRI targeted biopsy compared to standard TRUS biopsy in the repeat setting has been shown to be 1.45-1.62 higher. 4 However, in the setting of initial biopsy, the guidelines show that the relative sensitivity of mpMRI compared to TRUS biopsy is 0.97-1.15, correlating to no significant difference.4 The first randomized controlled trial published in the setting of initial biopsy demonstrated that mpMRI compared to standard systematic TRUS biopsy has a 59% vs. 54% overall diagnosis rate, respectively. Additionally, mpMRI has 44% clinically significant cancer detection rate compared to 49% of TRUS biopsy.5

The PROMIS study was a multicenter, paired - confirmatory cohort trial, comparing TRUS biopsy to mpMRI targeted biopsy using Likert score.6 This trial enrolled 576 patients with no previous biopsy and with a PSA <=15 ng/ml. If mpMRI were used as a triage test in biopsy-naïve patients with a high PSA (Likert>=3), the following results were shown: 27% fewer biopsies, 5% less insignificant cancer diagnosed, and 18% more significant cancer diagnosed in mpMRI targeted biopsies. The PRECISION trial 7 was a multicenter, randomized, noninferiority trial, comparing MRI-targeted biopsy vs. standard TRUS biopsy using PIRADS v2. Overall it enrolled 500 patients, in 25 centers, both academic and non-academic, in 11 countries. All patients had no previous biopsy, and a PSA<=20 ng/ml. In this trial, if mpMRI were used as a triage test in biopsy-naïve patients with increased PSA (PIRADS >=3), the results demonstrated: 28% fewer biopsies, 13% less insignificant cancer diagnosed, and 12% more significant cancer diagnosed in the mpMRI targeted biopsy. There are currently at least four ongoing trials attempting to answer the questions whether mpMRI can function as a triage test and avoid biopsies. These include:

  1. 4M trial (Barentsz, Netherlands)
  2. MRI-FIRST -trial (Rouviere, France)
  3. PROKOMB-trial (Baur, Berlin)
  4. MVP-trial (Nam, Canada)
This interesting overview was summarized by Dr. Villeirs, stating that to date, mpMRI is recommended only after a previous negative biopsy, and there is promising data the in biopsy-naïve patients, mpMRI used as a triage test will results in the performance of fewer biopsies overall, with more significant cancers and less insignificant cancers diagnosed.

Presented by: Geert Villeirs, Ghent, Belgium

References:
1. Woo et al. Eur Urol 2017; 72:177
2. Mehralivand S et al. J Urol. 2017; 198: 583
3. Wegelin et al. Eur Urol 2018; 71:517
4. Schoots, et al. Eur Urol 2015; 68:438
5. Panabianco et al. Urol Oncol 2015; 33: 17.e1-7
6. Ahmed et al. Lancet 2017; 389:815
7. Kasivisvanathan et al. NEJM  2018

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the 2nd EAU Update on Prostate Cancer  (PCa18)– September 14-15, 2018 – Milan, Italy