Magnetic resonance imaging of the prostate and targeted biopsy, Comparison of PIRADS and Gleason grading

IntroductionMultiparametric magnetic resonance imaging (mpMRI) of the prostate has become integral in the investigation of suspected prostate cancer. Regions of interest are graded using the PIRADS scoring system, and in our institution, lesions graded as PIRADS 3-5 undergo sampling by MRI-guided biopsy. Limited data currently exists on PIRADS grading and biopsy results. MethodsRetrospective review of 343 MRI-guided biopsies (MRGB) performed between April 2013 and December 2016 was conducted. This included patients irrespective of whether they were biopsy naive, biopsy negative or known low-grade malignancy. A Gleason score (G) >= 3+4 was considered to reflect clinically significant disease (CSD). ResultsOf the 18 PIRADS 2 cases (at referrer request) who went to biopsy, 16 were negative and two had small volume Gleason 6 cancer. A total of 75 PIRADS 3 cases were biopsied with 88% negative or small volume Gleason 6 cancer, only 12% yielded G 3+4. Of the 133 PIRADS 4 lesions, 24% were negative, 25% were G6 and 51% were G 3+4. A total of 117 PIRADS 5 cases were biopsied with 7% negative, 13% Gleason 6 and 80% considered significant ( G 3+4). Of all biopsies, 230 (67%) had a positive result (G6) with 171 of these (75%) being considered CSD, with overall CSD of 50% (171/343). ConclusionsThis paper demonstrates the incidence of CSD for different PIRADS grades. The low incidence of CSD in PIRADS 3 lesions suggests that in low clinical risk men, follow up in priority to biopsy may be an alternative treatment pathway.