Prospective Assessment of Prostate Cancer Aggressiveness Using 3-T Diffusion-Weighted Magnetic Resonance Imaging-Guided Biopsies Versus a Systematic 10-Core Transrectal Ultrasound Prostate Biopsy Cohort

BACKGROUND: Accurate pretreatment assessment of prostate cancer (PCa) aggressiveness is important in decision making. Gleason grade is a critical predictor of the aggressiveness of PCa. Transrectal ultrasound-guided biopsies (TRUSBxs) show substantial undergrading of Gleason grades found after radical prostatectomy (RP). Diffusion-weighted magnetic resonance imaging (MRI) has been shown to be a biomarker of tumour aggressiveness. OBJECTIVE: To improve pretreatment assessment of PCa aggressiveness, this study prospectively evaluated MRI-guided prostate biopsies (MR-GBs) of abnormalities determined on diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC) maps. The results were compared with a 10-core TRUSBx cohort. RP findings served as the gold standard. DESIGN, SETTING, AND PARTICIPANTS: A 10-core TRUSBx (n=64) or MR-GB (n=34) was used for PCa diagnosis before RP in 98 patients. MEASUREMENTS: Using multiparametric 3-T MRI: T2-weighted, dynamic contrast-enhanced imaging, and DWI were performed to identify tumour-suspicious regions in patients with a negative TRUSBx. The regions with the highest restriction on ADC maps within the suspicions regions were used to direct MR-GB. A 10-core TRUSBx was used in a matched cohort. Following RP, the highest Gleason grades (HGGs) in biopsies and RP specimens were identified. Biopsy and RP Gleason grade results were evaluated using chi-square analysis. RESULTS AND LIMITATIONS: No significant differences on RP were observed for proportions of patients having a HGG of 3 (35\% vs 28\%; p=0.50), 4 (32\% vs 41\%; p=0.51), and 5 (32\% vs 31\%; p=0.61) for the MR-GB and TRUSBx cohort, respectively. MR-GB showed an exact performance with RP for overall HGG: 88\% (30 of 34); for TRUS-GB it was 55\% (35 of 64; p=0.001). In the MR-GB cohort, an exact performance with HGG 3 was 100\% (12 of 12); for HGG 4, 91\% (10 of 11); and for HGG 5, 73\% (8 of 11). The corresponding performance rates for TRUSBx were 94\% (17 of 18; p=0.41), 46\% (12 of 26; p=0.02), and 30\% (6 of 20; p=0.01), respectively. CONCLUSIONS: This study shows prospectively that DWI-directed MR-GBs significantly improve pretreatment risk stratification by obtaining biopsies that are representative of true Gleason grade.