Evaluation of the PI-RADS Scoring System for mpMRI of the Prostate: A Whole-Mount Step-Section Analysis

World J Urol. 2015 Jul;33(7):1023-30. doi: 10.1007/s00345-014-1370-x. Epub 2014 Aug 1.

Abstract

Purpose: Evaluation of the Prostate Imaging Reporting and Data System (PI-RADS) scoring system for classifying multi-parametric magnetic resonance imaging findings of the prostate using whole-mount step-section slides as reference standard.

Materials and methods: Prospective inclusion of 50 consecutive patients with biopsy-proven prostate cancer (PCa). All patients received a multi-parametric MRI of the prostate, consisting of T2-weighted, diffusion-weighted, and dynamic contrast-enhanced MRI. After prostatectomy, all prostates were prepared as whole-mount step-section slides. For each patient, six lesions were predefined on whole-mount step-sections according to a distinct scheme and the corresponding regions were identified on MRI. Each lesion then was scored on MRI according to PI-RADS by an experienced blinded uro-radiologist and compared with histopathological findings.

Results: PCa received significant (p < 0.01) higher overall PI-RADS scores (4.10 ± 0.75) compared with benign changes (2.00 ± 0.74). In the peripheral zone, each single modality score showed good diagnostic accuracy for PCa detection (area under the curve [AUC] > 0.90). When combining all single modality scores, an even higher discriminative ability of PCa detection (AUC = 0.97, 95 % CI 0.95-0.99) could be achieved. In contrast, in the transitional zone, dynamic contrast-enhanced MRI (DCE) showed very low diagnostic accuracy (AUC = 0.60). Regarding tumor malignancy, no high-grade PCa (Gleason >7a) was present at PI-RADS scores <4 and no Gleason 6 PCa at a PI-RADS score of 5.

Conclusion: The PI-RADS scoring system showed good diagnostic accuracy: Only PI-RADS 4 and 5 showed high-grade PCa. However, it seems necessary to revise the PI-RADS scoring system concerning DCE in the transitional zone.

MeSH terms

  • Aged
  • Carcinoma / pathology*
  • Carcinoma / surgery
  • Humans
  • Image Interpretation, Computer-Assisted*
  • Magnetic Resonance Imaging*
  • Male
  • Middle Aged
  • Neoplasm Grading
  • Neoplasm Staging
  • Predictive Value of Tests
  • Prospective Studies
  • Prostatectomy
  • Prostatic Neoplasms / pathology*
  • Prostatic Neoplasms / surgery
  • ROC Curve