EAU 2019: The Imaging Specialist’s Perspective on MRI for Prostate Cancer

Barcelona, Spain (UroToday.com) Dr. Rouviere presented the imaging specialist’s perspective on MRI use in prostate cancer. According to the European Association of Urology (EAU) guidelines prostate multiparametric MRI (mpMRI) was originally recommended after a negative prostate biopsy before a repeat biopsy (2015). Later, mpMRI was recommended before a confirmatory biopsy in candidates for active surveillance (2016), and recently it has been recommended before a first set of biopsy, in biopsy naïve men (2019).

There are two possible clinical pathways :
  1. The combined pathway -if the mpMRI is positive – the patient undergoes a systematic +targeted biopsy, and if the mpMRI is negative – the patient undergoes only a systematic biopsy.
  2. The MRI pathway – if the mpMRI is positive – the patient undergoes a targeted biopsy and if the mpMRI is negative, the patient undergoes no biopsy.
It is important to understand the added value of the systematic biopsy. There are two relevant multicenter prospective trials – the MRI-FIRST1 and the 4M trial2. Additionally, there is a very pertinent Cochrane Meta-analysis3. The diagnosis of clinically significant cancers (>=Gleason grade group 2) in these trials for biopsy-naïve men are shown in figure 1. These results show that systematic biopsies retain substantial added value in biopsy naïve patients and cannot be omitted at this point for these specific population. However, a systematic biopsy might be omitted in case of repeat biopsy.

Figure 1 – Results of important trials in biopsy naïve patients, ISUP >=2 cancers:
EAU2019 UroToday biopsy naive patients

Many times, the systematic biopsies are negative and are responsible for the over-detection of indolent cancers. MpMRI specificity is low and a substantial part of PIRADS 3 and 4 lesions are benign. It is important to ask if it is possible to better predict the patients who need a (systematic or targeted) biopsy?

The negative predictive value of mpMRI is good in most studies,4 but it decreases when the pre-test risk of disease increases (figure 2).5 This means that if the risk of clinically significant disease is high, the results of the mpMRI cannot be trusted. In contrast, the positive predictive value of mpMRI increases as the pre-test risk of disease increases (figure 3).5 This means that a moderately positive mpMRI (PIRADS 3 or 4) in a low-risk patient, might not need a biopsy at all. In the near future, risk calculators combining clinical data, mpMRI findings, and biomarkers will be used to decide who needs to be biopsied. Hopefully, this approach will reduce the number of biopsies and the over-detection of ISUP grade 1 cancers (Gleason grade group 1), while maintaining, or even improving the detection of clinically significant prostate cancer.

Figure 2 – Negative predictive value of mpMRI:
EAU2019 UroToday Negative predictive value of mpMRI

Figure 3 – Positive predictive value of mpMRI:
EAU2019 UroToday Positive predictive value of mpMRI

Dr. Rouviere continued and stated that the accuracy of the targeted method is not optimal, despite MRI/US fusion. It is needed to improve this accuracy, or at least assess the minimal number of targeted cores to be taken depending on the size of the mpMRI lesion, its position, and the prostate volume. Obtaining only 1-2 cores form a suspicious mpMRI lesion is not sufficient, and a “saturation biopsy” of mpMRI suspicious prostate areas may be necessary.

The last topic discussed was the reproducibility of mpMRI interoperation. Despite the use of the PIRADS version 2 scoring system, inter-reader reproducibility is moderate at best. The are some initiatives to try and improve mpMRI interpretation. These include a certification process for radiologists – ESUR/EAU initiative, and using a quantitative mpMRI, which means replacing subjective assessment of PIRADS categories by quantitative MRI parameters. Using computer-assisted diagnosis systems will also improve mpMRI interpretation, and this will continue to evolve in the near future.

In conclusion, mpMRI is currently recommended before any prostate biopsy. Dr. Rouviere predicts that risk stratification will be used to decide who may deserve a biopsy after mpMRI. Additionally, the role of systematic biopsy will gradually decrease over time and it will remain necessary to obtain a substantial number of targeted cores from each lesion, to take into account the imprecision of the MRI/US fusion methods. Lastly, certification of radiologists and the use of quantitative mpMRI will improve the reproducibility of interpretation.

Presented by: Olivier Rouvière, MD, PhD, Professor, Department of Urinary and Vascular Imaging, Centre Hospitalier Universitaire de Lyon, Lyon, France

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre @GoldbergHanan at the 34th European Association of Urology (EAU 2019) #EAU19 conference in Barcelona, Spain, March 15-19, 2019. 

1. Rouviere O et al. Use of prostate systematic and targeted biopsy on the basis of multiparametric MRI in biopsy-naive patients (MRI-FIRST): a prospective, multicentre, paired diagnostic study. Lancet Oncol. 2019 Jan;20(1):100-109. doi: 10.1016/S1470-2045(18)30569-2. Epub 2018 Nov 21.
2. Van der Leest et al. Head-to-head Comparison of Transrectal Ultrasound-guided Prostate Biopsy Versus Multiparametric Prostate Resonance Imaging with Subsequent Magnetic Resonance-guided Biopsy in Biopsy-naïve Men with Elevated Prostate-specific Antigen: A Large Prospective Multicenter Clinical Study. European Urology. Volume 75, Issue 4, April 2019, Pages 570-578
3. Droost FJH, et al. Cochrane database of systematic reviews 2019
4. Moldovan PC et al. What Is the Negative Predictive Value of Multiparametric Magnetic Resonance Imaging in Excluding Prostate Cancer at Biopsy? A Systematic Review and Meta-analysis from the European Association of Urology Prostate Cancer Guidelines Panel. Eur Urol. 2017 Aug;72(2):250-266. doi: 10.1016/j.eururo.2017.02.026. Epub 2017 Mar 21.
5. Rouviere O et al. The current role of prostate multiparametric magnetic resonance imaging Diagn Interv Imaging 2018