Prognostic value of Prostate Imaging and Data Reporting System (PI-RADS) v. 2 assessment categories 4 and 5 compared to histopathological outcomes after radical prostatectomy.

To assess Prostate Imaging and Data Reporting System (PI-RADS) v. 2 score 4/5 lesions compared to Gleason score (GS) and stage after radical prostatectomy (RP) and to validate the proposed 15-mm size threshold that differentiates category 4 versus 5 lesions.

With Institutional Review Board (IRB) approval, 140 men underwent 3T magnetic resonance imaging (MRI) and RP between 2012-2015. Two blinded radiologists: 1) assigned PI-RADS v. 2 scores, 2) measured tumor size on axial T2 -weighted-MRI, and 3) assessed for extraprostatic extension (EPE). Interobserver agreement was calculated and consensus diagnoses achieved through reference standard (MRI-RP maps). PI-RADS v. 2 scores and tumor size were compared to GS and stage using chi-square, analysis of variance (ANOVA), and receiver operating characteristic (ROC) curve analysis.

In all, 80.7% (113/140) of tumors were category 4 (n = 45) or 5 (n = 68) lesions (κ = 0.45). Overall tumor size was 18.2 ± 7.7 mm and category 5 lesions were larger (22.6 ± 6.8 versus 11.5 ± 1.9 mm, P < 0.001). High-risk (GS ≥8) tumors were larger than low- and intermediate-risk tumors (P = 0.016) and were more frequently, but not significantly so, category 5 lesions (78.9% [15/19] vs. 22.1% [4/10], P = 0.18). 67.3% (76/113) of patients had EPE. Category 5 lesions were strongly associated with EPE (P < 0.0001). Area under the ROC curve for diagnosis of EPE by size was 0.74 (confidence interval 0.64-0.83), with size ≥15 mm yielding a sensitivity/specificity of 72.4/64.9%. Size improved sensitivity for diagnosis of EPE compared to subjective assessment (sensitivity/specificity ranging from 46.1-48.7%/70.3-86.5%, κ = 0.29) (P = 0.028).

PI-RADS v. 2 category 5 lesions are associated with higher Gleason scores and EPE. A 15-mm size threshold is reasonably accurate for diagnosis of EPE with increased sensitivity compared to subjective assessment.

3 J. Magn. Reson. Imaging 2016.

Journal of magnetic resonance imaging : JMRI. 2016 Nov 03 [Epub ahead of print]

Christopher S Lim, Matthew D F McInnes, Robert S Lim, Rodney H Breau, Trevor A Flood, Satheesh Krishna, Christopher Morash, Wael M Shabana, Nicola Schieda

Ottawa Hospital, University of Ottawa, Department of Radiology, Civic Campus C1, Ottawa, Ontario, Canada., Ottawa Hospital, University of Ottawa, Division of Urology, Department of Surgery, General Campus, Ottawa, Ontario, Canada., Ottawa Hospital, University of Ottawa, Department of Anatomical Pathology, General Campus, Ottawa, Ontario, Canada., Ottawa Hospital, University of Ottawa, Department of Radiology, Civic Campus C1, Ottawa, Ontario, Canada. .

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