Performance of multiparametric MRI in men at risk of prostate cancer before the first biopsy: a paired validating cohort study using template prostate mapping biopsies as the reference standard

Abstract

Background: Multiparametric magnetic resonance imaging (mpMRI) has the potential to serve as a non-invasive triage test for men at risk of prostate cancer. Our objective was to determine the performance characteristics of mpMRI in men at risk before the first biopsy using 5 mm template prostate mapping (TPM) as the reference standard.

Methods: One hundred and twenty-nine consecutive men with clinical suspicion of prostate cancer, who had no prior biopsy, underwent mpMRI (T1/T2-weighted, diffusion-weighting, dynamic contrast enhancement) followed by TPM. The primary analysis used were as follows: (a) radiological scores of suspicion of ≥3 attributed from a five-point ordinal scale, (b) a target condition on TPM of any Gleason pattern ≥4 and/or a maximum cancer core length of ≥4 mm and (c) two sectors of analysis per prostate (right and left prostate halves). Secondary analyses evaluated the impact of changing the mpMRI score threshold to ≥4 and varying the target definition for clinical significance.

Results: One hundred and forty-one out of 258 (55%) sectors of analysis showed 'any cancer' and 77/258 (30%) had the target histological condition for the purpose of deriving the primary outcome. Median (with range) for age, PSA, gland volume and number of biopsies taken were 62 years (41-82), 5.8 ng ml(-1) (1.2-20), 40 ml (16-137) and 41 cores (20-93), respectively. For the primary outcome sensitivity, specificity, positive and negative predictive values and area under the receiver-operating curve (with 95% confidence intervals) were 94% (88-99%), 23% (17-29%), 34% (28-40%), 89% (79-98%) and 0.72 (0.65-0.79), respectively.

Conclusions: MpMRI demonstrated encouraging diagnostic performance characteristics in detecting and ruling out clinically significant prostate cancer in men at risk, who were biopsy naive.

Figures

Figure 1

Axial images from a positive MRI (scoring 5/5) with a maximum of 5 mm, 50%, of Gleason 3+4 found at template biopsy in the right posterior apical parasagittal zone. The T2 image (a) shows a low signal focus on the right (arrow), the contrast-enhanced image (b) shows corresponding focal enhancement (arrow), the Apparent Diffusion Coefficient (ADC) map (c) shows significantly restricted diffusion (arrow) and there is a focus of high signal on the long b diffusion image (b-1400) (arrow, d). Note that although the transition zone (arrowhead) enhances moderately and shows mildly restricted diffusion, it is not of high signal on the long b value images (d).

Figure 2

Axial images from an indetermnate MRI (scoring 3/5) with no tumour found at biopsy. The T2 image (a) shows diffuse, but slightly heterogenous, moderate reduction in signal in the peripheral zone on each side (arrows). The contrast-enhanced image (b) shows moderate enhancement in a similar distribution (arrows). No significantly restricted diffusion is seen on the ADC map (c) and long b diffusion image (d).