Detection of Gleason 6 prostate cancer in patients with clinically significant prostate cancer on multiparametric magnetic resonance imaging

INTRODUCTION: Multiparametric-Magnetic Resonance Imaging (mpMRI)-Ultrasound fusion guided biopsy (Fbx) has emerged as the newstandard of risk stratification for prostate cancer (PCa) with superior detection rates of clinically significant PCa than randomized biopsy. In the present study, we evaluated patients with suspicion of clinically significant PCa on mpMRI, but histopathologically proven Gleason 6 PCa in Fbx. MATERIAL AND METHODS: Between 2015 and 2019, 849 patients underwent Fbx and concurrent systematic 12-core biopsy at our department. 234 patients were diagnosed with Gleason 6 PCa in either mpMRI-targeted and/or concurrent systematic biopsy. Patients were analyzed regarding PSA, mpMRI findings according to PI-RADS classification, histopathological results of Fbx and systematic 12-core biopsy. 99/234 patients were also analyzed in regards of histopathology of the whole-mount specimen of subsequent radical prostatectomy (RP). RESULTS: In 131/234 patients (56%), Gleason 6 PCa was detected in the mpMRI target. In 103/234 patients (44%), Gleason 6 PCa was detected in the concurrent systematic 12-core biopsy with negative mpMRI-targeted biopsy. Men with evidence of Gleason 6 in the mpMRI target had significantly higher amounts of overall positive biopsies (median 4 vs. 2, p < 0.001) and higher maximum tumor infiltration per biopsy core (30% vs. 20%, p < 0.001) compared to men with negative mpMRI-targeted biopsy. Detection of Gleason 6 in mpMRI Target lesions correlated significantly with the PI-RADS score (p < 0.001). Patients with positive mpMRI-target had significantly higher tumor infiltration in whole-mount specimen after prostatectomy (20% vs. 15%, p = 0.0026) compared to men without detection of Gleason 6 in mpMRI-targeted biopsy but in additional systematic biopsy. CONCLUSION: Detection of Gleason 6 PCa in mpMRI-targeted biopsy indicates higher tumor burden compared to detection of Gleason 6 PCa in concurrent systematic biopsy and negative mpMRI-targeted biopsy.