UCLA

Purpose

Magnetic resonance imaging (MRI) guidance may improve the accuracy of Gleason score (GS) determination by directing the biopsy to regions of interest (ROI) that are likely to harbor high-grade prostate cancer (CaP). The aim of this study was to determine the frequency and predictors of GS upgrading when a subsequent MRI-guided biopsy is performed on patients with a diagnosis of GS 6 disease on the basis of conventional, transrectal ultrasound-guided biopsy.

Methods and materials

A consecutive series of 245 men with a diagnosis of low-risk CaP (ie, cT1c, GS 6, prostate-specific antigen <10) based on transrectal ultrasound-guided biopsy was enrolled in an active surveillance protocol that used subsequent MRI-guided biopsy for confirmation of GS. ROIs were categorized on a scale of 1 to 5. The Artemis ultrasound-MRI fusion device was used to perform targeted biopsies of ROIs as well as systematic biopsies from a software-based 12-point map. Predictors of GS upgrading were analyzed using univariate and multivariate analyses.

Results

Fusion biopsy resulted in 26% of patients having GS upgrading (GS 3+4 in 18%, 4+3 in 5%, and 8-9 in 3%). Of the 72% of patients with ROIs appropriate for targeting, targeted cores upgraded the GS in 18%, whereas systematic cores upgraded the GS in 24%. In patients without targeted biopsy, GS upgrading was seen in 14%. On multivariate analysis, a category 5 ROI was the most significant predictor of GS upgrading with an odds ratio of 10.56 (P < .01).

Conclusions

Nearly 25% of men with GS 6 CaP diagnosed by standard transrectal ultrasound biopsy may experience GS upgrading when a subsequent MRI-ultrasound fusion biopsy is performed. The most important single predictor of upgrading is a category 5 ROI on multiparametric MRI. GS upgrading may influence treatment decisions. Therefore, MRI-guided biopsy should be considered prior to formulating a management strategy in patients whose conventional biopsy reveals low-risk CaP.