EAU 2018: Simple Biparametric MRI in Detection and Ruling Out Significant Prostate Cancer in Biopsy-Naïve Men

Copenhagen, Denmark (UroToday.com) Dr. Boesen and colleagues presented results of simple biparametric MRI (bpMRI) for detecting prostate cancer in biopsy-naïve men. Standard transrectal ultrasound-guided biopsies in men with clinical suspicion of prostate cancer are prone to sampling errors due to difficulties in target identification. Multiparametric MRI (mpMRI) has been shown to improve detection and risk stratification of prostate cancer. However, mpMRI is time-consuming and costly. A simpler and rapid (~15 min) biparametric MRI (bpMRI) using fewer scan sequences and no intravenous contrast-media could provide a basis for a prostate MRI triage test before any biopsy in a large scale. The objective of this study was to prospectively assess the diagnostic accuracy and negative predictive value (NPV) of a novel bpMRI method in biopsy-naive men in detection and ruling out significant prostate cancer in confirmatory biopsies.

For this study, the BIDOC (biparametric MRI for detection of prostate cancer) study included 1,020 men with clinical suspicion of prostate cancer between November 2015 and June 2017. All patients provided written informed consent and underwent bpMRI (T2-weighted and diffusion-weighted imaging) followed by systematic biopsy (all men) and bpMRI targeted biopsies in men with moderately/highly suspicious bpMRIs. BpMRI suspicion grade and biopsy results were compared, and the definition of significant prostate cancer was any core with Gleason score ≥7 (4+3) or maximum cancerous-core-length >50% of Gleason score 7 (3+4). Prostate cancer detection rates combining systematic biopsy and targeted biopsy were used as reference standard.

Overall, prostate cancer was detected in 64% of men amongst whom 40% had significant prostate cancer. There was no significant difference in detection of significant prostate cancer comparing systematic biopsy to targeted biopsy (34% vs. 33%; p=0.271), but systematic biopsy detected significantly more men with insignificant prostate cancer (28% vs. 14%; p<0.001). Restricting biopsy to men with moderately/highly suspicious bpMRIs meant: 30% of men could have avoided prostate biopsies, significant prostate cancer diagnoses were improved by 13%, and insignificant prostate cancer diagnoses were reduced by 40% compared with systematic biopsy alone. The NPV of a low-suspicion bpMRI was 99%, considering that only eight men with a low-suspicion bpMRI had significant prostate cancer on systematic biopsy.

Dr. Boesen concluded that a low-suspicion bpMRI has a high NPV in ruling out significant prostate cancer on confirmatory biopsies in biopsy-naive men. Combining targeted biopsy and systematic biopsy only in men with moderately/highly suspicious bpMRIs is the preferred approach and allows for 30% of men to safely avoid prostate biopsies, improves significant prostate cancer diagnosis by 13% and reduces insignificant prostate cancer diagnosis by 40% compared to the current diagnostic standard ─ systematic biopsy in all men. Using bpMRI as a triage test improves risk stratification and may be used to exclude aggressive disease and avoid biopsies with its inherent risks.

Presented by: Lars P. Boesen, Herlev Gentofte University Hospital, Herlev, Denmark

Co-Authors: Nørgaard N, Løgager V, Balslev I, Thestrup K-C, Winther M, Bisbjerg R, Jakobsen H, Thomsen H

Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, twitter: @zklaassen_md at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark

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