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

Date Published: June 3, 2019

Publisher: Public Library of Science

Author(s): Ivan Jambor, Janne Verho, Otto Ettala, Juha Knaapila, Pekka Taimen, Kari T. Syvänen, Aida Kiviniemi, Esa Kähkönen, Ileana Montoya Perez, Marjo Seppänen, Antti Rannikko, Outi Oksanen, Jarno Riikonen, Sanna Mari Vimpeli, Tommi Kauko, Harri Merisaari, Markku Kallajoki, Tuomas Mirtti, Tarja Lamminen, Jani Saunavaara, Hannu J. Aronen, Peter J. Boström, Ricky W. Johnstone

Abstract: BackgroundMagnetic 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 findingsThe 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.ConclusionsIMPROD bpMRI demonstrated a high NPV for SPCa in men with a clinical suspicion of PCa in this prospective multi-institutional clinical trial.Trial NCT02241122.

Partial Text: Prostate cancer (PCa) is the most common solid organ cancer in men in Europe [1]. In contrast to the detection protocol for many other solid organ cancers, the decision of whom to biopsy among patients with a clinical suspicion of PCa has historically not been based on imaging findings [2]. The standard diagnostic pathway has relied on prostate specific antigen (PSA) levels and digital rectal examination (DRE) findings to determine if a man should undergo transrectal ultrasound-guided (TRUS) biopsies [2]. This pathway is well known to result in unnecessary biopsies, overdetection of nonsignificant PCa (non-SPCa), and underdetection of clinically significant PCa (SPCa) [2].

Recruitment of the trial population is described in Fig 1. Of the 364 men recruited, 14 withdrew their consent before and 10 after MRI. Two men were excluded due to non-diagnostic IMPROD bpMRI studies caused by rectal-gas-related artifacts on DWI. The majority of the patients who withdrew their consent were either claustrophobic or gave no specific reason for withdrawing.

In this multi-institutional trial, the clinical utility of a rapid biparametric pre-biopsy MRI (IMPROD bpMRI) in men with a clinical suspicion of PCa has been prospectively validated. IMPROD bpMRI demonstrated a high NPV for SPCa in both trials (MULTI-IMPROD trial [NCT02241122] and IMPROD [NCT01864135]).



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