Validation of IMPROD biparametric MRI in men with clinically suspected prostate cancer: A prospective multi-institutional trial

Abstract

Background: Magnetic resonance imaging (MRI) combined with targeted biopsy (TB) is increasingly used in men with clinically suspected prostate cancer (PCa), but the long acquisition times, high costs, and inter-center/reader variability of routine multiparametric prostate MRI limit its wider adoption.

Methods and findings: The aim was to validate a previously developed unique MRI acquisition and reporting protocol, IMPROD biparametric MRI (bpMRI) (NCT01864135), in men with a clinical suspicion of PCa in a multi-institutional trial (NCT02241122). IMPROD bpMRI has average acquisition time of 15 minutes (no endorectal coil, no intravenous contrast use) and consists of T2-weighted imaging and 3 separate diffusion-weighed imaging acquisitions. Between February 1, 2015, and March 31, 2017, 364 men with a clinical suspicion of PCa were enrolled at 4 institutions in Finland. Men with an equivocal to high suspicion (IMPROD bpMRI Likert score 3-5) of PCa had 2 TBs of up to 2 lesions followed by a systematic biopsy (SB). Men with a low to very low suspicion (IMPROD bpMRI Likert score 1-2) had only SB. All data and protocols are freely available. The primary outcome of the trial was diagnostic accuracy-including overall accuracy, sensitivity, specificity, negative predictive value (NPV), and positive predictive value-of IMPROD bpMRI for clinically significant PCa (SPCa), which was defined as a Gleason score ≥ 3 + 4 (Gleason grade group 2 or higher). In total, 338 (338/364, 93%) prospectively enrolled men completed the trial. The accuracy and NPV of IMPROD bpMRI for SPCa were 70% (113/161) and 95% (71/75) (95% CI 87%-98%), respectively. Restricting the biopsy to men with equivocal to highly suspicious IMPROD bpMRI findings would have resulted in a 22% (75/338) reduction in the number of men undergoing biopsy while missing 4 (3%, 4/146) men with SPCa. The main limitation is uncertainty about the true PCa prevalence in the study cohort, since some of the men may have PCa despite having negative biopsy findings.

Conclusions: IMPROD bpMRI demonstrated a high NPV for SPCa in men with a clinical suspicion of PCa in this prospective multi-institutional clinical trial.

Trial registration: ClinicalTrials.gov NCT02241122.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. Study flowchart for men undergoing both targeted and systematic biopsy.

bpMRI, biparametric magnetic resonance imaging; GS, Gleason score.

Fig 2. Comparison of biopsy findings from systematic 12-core biopsy and biparametric MRI targeted biopsy (2 cores per lesion, up to 2 lesions per man).

Biopsy findings per patient of systematic 12-core biopsy compared with IMPROD biparametric MRI targeted biopsy for the total cohort of 338 men. Yellow shading indicates men in whom targeted biopsy upgraded the PCa risk category in relation to systematic 12-core biopsy. Dark yellow indicates cases in which the upgrade was to an intermediate or high-risk category. Teal shading indicates men in whom systematic 12-core biopsy upgraded PCa risk category in relation to targeted biopsy (or no biopsy based on non-suspicious MRI). Dark teal indicates cases in which the upgrade was to an intermediate or high-risk category.