Elsevier

European Urology

Volume 61, Issue 1, January 2012, Pages 177-184
European Urology

Prostate Cancer
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

https://doi.org/10.1016/j.eururo.2011.08.042Get rights and content

Abstract

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.

Introduction

The Gleason grading system is the key method to describe the pathologic characteristics of prostate cancer (PCa). Of all the clinically determinable parameters, the Gleason score (GS) has proven to be the most important in measuring aggressiveness, disease outcome, and the risk of mortality from PCa [1].

Transrectal ultrasoundguided biopsy (TRUSBx) is currently the most accepted method for establishing a definite diagnosis of PCa in patients with a clinical suspicion based on prostate-specific antigen (PSA) values or digital rectal examination (DRE). The most frequently used schemes include sampling 10–12 cores with emphasis on the lateral peripheral zone and transition zone [2], [3]. The tumour biopsy cores are scored according to the Gleason grading scheme to determine aggressiveness.

PCa can be multifocal and heterogeneous in composition, often presenting with well-, moderately, and poorly differentiated components in the same tumour. TRUSBx-determined GS has been shown [4], [5], [6] to be substantially discordant (undergrading in 34–38%) with the GS determined in radical prostatectomy (RP) specimens. Because risk stratification affects individualised treatment decisions and prognosis, the accurate pretreatment prediction of GS remains essential.

Multiparametric MR imaging (MP-MRI), including T2-weighted imaging, diffusion-weighted imaging (DWI), and dynamic contrast-enhanced MR imaging (DCE-MRI), have all been shown (especially in combination) to localise PCa accurately [7], [8]. Improved localisation of suspicious regions on MP-MRI have also been biopsy targeted under MR guidance and shown to increase tumour detection rates substantially [9], [10]. DWI has been shown to provide information about tumour aggressiveness [11], [12].

The aim of this study was to determine prospectively whether DWI-guided prostate biopsies could improve the pretreatment assessment of PCa aggressiveness. These results were compared with a standard clinical cohort of patients who underwent 10-core TRUSBxs. In both cohorts the performance of Gleason grades in biopsy and RP (the gold standard) was determined.

Section snippets

Patients

Between August 2006 and April 2009, 123 consecutive patients underwent RP at the Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, and were retrospectively included after a PCa diagnosis was made with 10-core TRUSBx or MR-GB. Patients with prior hormonal/radiotherapy were excluded.

Transrectal ultrasound–guided biopsy sampling

Extended systematic 10-core TRUSBxs (6 lateral and 4 transition zone) were obtained using a Pro Focus B-K ultrasound device (B-K Medical, Herlev, Denmark) and 18G needles with a 17-mm sampling length.

Results

Ninety-eight patients fulfilled the inclusion criteria. In 34 of 98 patients a tumour diagnosis was made using MR-GB (median: 3 cores, range: 1–5; median number of biopsies/TSR: 2, range: 1–3), and in 64 of 98 patients a diagnosis was made using 10-core TRUSBx. The median duration of the procedure for MR-GB was 29 min (range: 15–75 min). The median duration between MR-GB and RP was 6 wk (range: 3–11 wk) and between TRUSBx and RP was 5 wk (range: 2–9 wk). Table 2 summarises the patients’

Discussion

In this prospective study, 3-T DWI targeted MR-GB sampling improved the pretreatment assessment of PCa aggressiveness. The Gleason grades as determined with MR-GB showed a high performance rate (88%) with prostatectomy. This is in sharp contrast to 10-core TRUSBx, which showed a 55% performance rate. In this study the most abnormal ADC regions following MP-MRI localisation of tumour were used to target biopsies. To our knowledge, this is the first prospective report on the use of DWI to obtain

Conclusions

Biopsies targeted towards the most abnormal regions on 3-T DWI MR imaging represent a substantially improved method for the assessment of true tumour aggressiveness and can therefore represent an indispensable tool in the diagnosis and management of patients with PCa. This will probably also hold true for other malignancies. Thus its use is strongly advocated.

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