Performance and inter-observer variability of prostate MRI (PI-RADS version 2) outside high-volume centres

Abstract

<b>Objective:</b> Despite the growing trend to embrace pre-biopsy MRI in the diagnostic pathway for prostate cancer (PC), its performance and inter-observer variability outside high-volume centres remains unknown. This study aims to evaluate sensitivity of and variability between readers of prostate MRI outside specialized units with radical prostatectomy (RP) specimen as the reference standard.<b>Materials and methods:</b> Retrospective study comprising a consecutive cohort of all 97 men who underwent MRI and subsequent RP between January 2012 and December 2014 at a private hospital in Sweden. Three readers, blinded to clinical data, reviewed all images (including 11 extra prostate MRI to reduce bias). A tumour was considered detected if the overall PI-RADS v2 score was 3-5 and there was an approximate match (same or neighbouring sector) of tumour sector according to a 24 sector system used for both MRI and whole mount sections.<b>Results:</b> Detection rate for the index tumour ranged from 67 to 76%, if PI-RADS 3-5 lesions were considered positive and 54-66% if only PI-RADS score 4-5 tumours were included. Detection rate for aggressive tumours (GS ≥ 4 + 3) was higher; 83.1% for PI-RADS 3-5 and 79.2% for PI-RADS 4-5. The agreement between readers showed average [Formula: see text] values of 0.41 for PI-RADS score 3-5 and 0.51 for PI-RADS score 4-5.<b>Conclusions:</b> Prostate MRI evidenced a moderate detection rate for clinically significant PC with a rather large variability between readers. Clinics outside specialized units must have knowledge of their performance of prostate MRI before considering omitting biopsies in men with negative MRI.