CUA 2017: Magnetic Resonance Imaging-Targeted vs. Systematic Biopsies in Men on Active Surveillance: Results of a Prospective, Randomized Canadian Urology Research Consortium Trial

Toronto, Ontario ( Dr. Laurence Klotz presented the first report of a multicentre, prospective, randomized phase 3 trial (ASIST) attempting to determine if multiparametric magnetic resonance imaging (mpMRI) and targeted biopsy can improve selection of patients eligible for active surveillance. The question of the study was to see whether mpMRI and targeted biopsy improved detection of clinically significant cancer compared to systematic biopsy. The primary outcome was the proportion of subjects whose biopsy was upgraded at their confirmatory biopsy to Gleason score 7 (3 + 4) or higher. 

Eligible patients were diagnosed with favourable-risk prostate cancer (Gleason 6 and prostate-specific antigen [PSA] <10) within the previous 12 months. Out of the 296 registered patients, 273 were randomized between systematic 12-core biopsy and an MRI, with targeted and systematic biopsies, done between six and 13 months after the initial biopsy. There were no differences between treatment arms in terms of stratum, demographics, tumour characteristics, or prior treatments. 

Initial results demonstrated that 31 (23%) of trans-rectal ultrasound (TRUS)-guided biopsy patients had Gleason 7 or higher cancer compared with 29 (21.2%) of the MRI-guided biopsy (p=0.68). Independent, blinded pathology review was performed on 188 patients. Upgrading incorporating path review occurred in 36/132 (27.3%) of TRUS-guided and 42/127 (33.1%) of MRI-guided biopsy patients (p=0.34). The positive predictive value (PPV) for Gleason 7 or higher cancer for Prostate Imaging Reporting and Data System (PI-RADS) score 1‒2, 3,4, and 5 was 13%, 29%, 24%, and 33%, respectively.  2/12 (16.7%) with a MRI score of 1, and 3/33 (9%) with MRI score of 2 had Gleason 7 or higher cancers on systematic biopsy. The negative predictive value (NPV) of PI-RADS 1‒2 for Gleason ≥7 was 89%. 

If targeted biopsies only were performed in men with a PIRADS 3-5 target, 19/127 (15%) of patients would have been upgraded and 10/137 (7.3%, 95% CI 3.6-13%) would have been missed. If targeted and systemic biopsies were performed only in those with a PIRADS 3-5 lesion, clinically significant cancer would have missed in 3.6%.

In summary, no significant difference was observed in the rate of upgrading between confirmatory biopsy with TRUS compared with MRI-guided targeted biopsy. No secondary outcome was statistically significant. Performing confirmatory targeted biopsy only in men with a PI-RADS lesion ≥3 would identify 89% of Gleason 7 or greater cancers. Doing only targeted biopsies missed clinically significant cancers in 7% of patients. MRI with targeted biopsies will identify most, but not all men with higher Gleason grade. 

Presented By: Laurence H. Klotz, MD, University of Toronto, Toronto, Ontario, Canada

Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre   Twitter: @GoldbergHanan at the  72nd Canadian Urological Association Annual Meeting - June 24 - 27, 2017 - Toronto, Ontario, Canada