Assessment of Prostate MRI Before Prostate Biopsies

Background: Prostate cancer is difficult to detect using ultrasound. As a result, in case of suspicion of prostate cancer based on digital rectal examination (DRE) or Prostate Specific Antigen (PSA) level, it is currently recommended to perform "blinded" systematically distributed biopsies with 10-18 samples obtained from predefined locations in the gland.

These so-called systematic biopsies (SB) may lead to improper patient management by (i) missing clinically significant cancer, especially in the anterior half of the gland that tends to be undersampled, (ii) inducing chance detection of clinically insignificant cancer foci that may result in overtreatments, (iii) undersampling the tumor foci and thus underestimating their volume and aggressiveness.

Multiparametric Magnetic Resonance Imaging (mp-MRI) has yielded promising results in detecting aggressive (Gleason ≥7) prostate cancers. Several monocenter studies showed that targeted biopsies (TB) based on mp-MRI findings could detect significantly more aggressive cancers, reduce the diagnosis of clinically insignificant cancers, and better evaluate the aggressiveness of detected cancers than SB. However, these monocenter studies only provide low-level evidence and three recent independent reviews of literature concluded that there was a need for a robust multicenter trial evaluating the diagnostic yield of TB as compared to SB. This is particularly important since many academic and private centers in France already perform mp-MRI before prostate biopsy in daily routine. Therefore the risk is that this approach becomes the norm without being properly evaluated and it is crucial and urgent to perform a controlled multicentric study to provide high-level evidence as to whether mp-MRI should or should not be obtained before prostate biopsy.

One controlled multicentric study has been published recently in which SB and TB had been obtained by two different operators in 95 patients. TB yielded a significantly higher detection rate for all prostate cancers (69% vs 59%, p=0.033) and for clinically significant cancers (67% vs 52%, p=0.0011). However, this study was limited by the fact that patients with negative mp-MRI were not included.

Research hypotheses: There is currently no robust multicenter trial comparing prostate TB based on mp-MRI findings versus the current standard of care (SB). We propose a multicentre prospective trial comparing the results of SB and TB performed in the same patients by two independent operators. Our hypothesis is that TB detects aggressive (Gleason ≥7) cancers in a significantly higher percentage of patients than SB.

Main objective: To compare the percentage of patients with "clinically significant cancer" (using definition A, i.e. cancer with Gleason score ≥7) detected by SB versus TB.