Diagnostic accuracy of magnetic resonance imaging (MRI) prostate imaging reporting and data system (PI‐RADS) scoring in a transperineal prostate biopsy setting

Abstract

ObjectivesTo determine the sensitivity and specificity of multiparametric magnetic resonance imaging (mpMRI) for significant prostate cancer with transperineal sector biopsy (TPSB) as the reference standard. Patients and MethodsThe study included consecutive patients who presented for TPSB between July 2012 and November 2013 after mpMRI (T2-and diffusion-weighted images, 1.5 Tesla scanner, 8-channel body coil). A specialist uro-radiologist, blinded to clinical details, assigned qualitative prostate imaging reporting and data system (PI-RADS) scores on a Likert-type scale, denoting the likelihood of significant prostate cancer as follows: 1, highly unlikely; 3, equivocal; and 5, highly likely. TPSBs sampled 24-40 cores (depending on prostate size) per patient. Significant prostate cancer was defined as the presence of Gleason pattern 4 or cancer core length ≥6 mm. ResultsA total of 201 patients were included in the analysis. Indications were: a previous negative transrectal biopsy with continued suspicion of prostate cancer (n = 103); primary biopsy (n = 83); and active surveillance (n = 15). Patients' mean (±SD) age, prostate-specific antigen and prostate volumes were 65 (±7) years, 12.8 (±12.4) ng/mL and 62 (±36) mL, respectively. Overall, biopsies were benign, clinically insignificant and clinically significant in 124 (62%), 20 (10%) and 57 (28%) patients, respectively. Two of 88 men with a PI-RADS score of 1 or 2 had significant prostate cancer, giving a sensitivity of 97% (95% confidence interval [CI] 87-99) and a specificity of 60% (95% CI 51-68) at this threshold. Receiver-operator curve analysis gave an area under the curve of 0.89 (95% CI 0.82-0.92). The negative predictive value of a PI-RADS score of ≤2 for clinically significant prostate cancer was 97.7% ConclusionWe found that PI-RADS scoring performs well as a predictor for biopsy outcome and could be used in the decision-making process for prostate biopsy.

Diagnostic value of MRI-based PSA density in predicting transperineal sector-guided prostate biopsy outcomes

“…Two additional outcomes which represented significant cancer were assessed as follows: Gleason pattern 4 and/or maximum cancer core length (MCCL) of >4mm, referred to as Definition G4 and Gleason pattern 4 and/or MCCL >6mm, referred to as Definition G6 [16]. These lengths of core involvement were selected as they are representative of a lesion volume of 0.2ml (4mm) and 0.5ml (6mm) [24].…”

“…These lengths of core involvement were selected as they are representative of a lesion volume of 0.2ml (4mm) and 0.5ml (6mm) [24]. These volumes are below the calculated threshold of 1.3ml for significant tumour volume, as per the European Randomised study of Screening for Prostate Cancer [16,24].…”

“…While only T2 sequences are required for disease staging and prostate volume assessment, our index test uses a 1.5 Tesla magnet and two straightforward and resource-friendly sequences: T2-weighted imaging and DWI [16,32]. We recently demonstrated a high sensitivity (97%) for Prostate ImagingReporting and Data System (PI-RADS) at a threshold score of ≤2 [16]; therefore, in the absence of contraindications, all our patients now receive mpMRI prior to TPSB. This ability of MRI to detect clinically significant lesions has led to its adoption in many centres [33].…”

“…The addition of multiparametric MRI (mpMRI) sequences such as diffusion weighted imaging (DWI) and dynamic contrast enhancement (DCE) has led to some centres performing MRI as part of the initial diagnostic pathway [16,17]. In fact, the recent PROMIS (Prostate MR imaging study) randomised controlled trial found mpMRI to have greater sensitivity (93%) compared to conventional TRUS-guided transrectal biopsy (48%) [18].…”

“…With pre-biopsy MRI, prostate volume can be estimated accurately and noninvasively, with studies demonstrating improved accuracy in MR-derived volume assessment and reduced intraobserver variability compared to TRUS [19,20]. The majority of prostate MRI studies have focussed on the utility of additional sequences, excluding the additional utility of PSAD [16,21].…”