Role of PI‐RADSv2 with multiparametric MRI in determining who needs active surveillance or definitive treatment according to PRIAS

Purpose To evaluate the role of Prostate Imaging Reporting and Data System v. 2 (PI‐RADSv2) in triaging patients with prostate cancer according to Prostate Cancer Research International: Active Surveillance (PRIAS). Materials and Methods Between January 2012 and December 2014, 456 patients with biopsy‐proven cancer underwent multiparametric 3T magnetic resonance imaging (MRI) using T 2 ‐weighted, diffusion‐weighted, and dynamic contrast‐enhanced MRI sequences, and then radical prostatectomy. Two radiologists independently reviewed MR images using PI‐RADSv2. For AS, PRIAS required clinical stage <T3, prostate‐specific antigen (PSA) ≤10 ng/mL, PSA density <0.2 ng/mL 2 , Gleason score (GS) ≤6, and the number of positive cores ≤2. For AS, PI‐RADSv2 required an index lesion scored <4. Standard reference was prostatectomy, in which insignificant cancer was defined as a small (<0.5 cm 3 ) organ‐confined lesion with GS ≤6. Sensitivity and specificity for insignificant cancer were obtained with PRIAS, PI‐RADSv2, and both. Results The sensitivity and specificity with PRIAS were 82.9% (68/82) and 70.9% (265/374), respectively. PI‐RADSv2 decreased the sensitivity to 61% (50/82) to 80.5% (66/82), but increased the specificity to 77.8% (291/374) to 90.8% (340/374). The combination of PRIAS and PI‐RDASv2 increased significantly the specificity to 89.6% (335/374) to 92.8% (347/374) ( P < 0.001). Conclusion PRIAS using multiparametric MRI can identify a greater number of insignificant cancers than PI‐RADSv2. However, PI‐RADSv2 helps detect many significant cancers that are misdiagnosed as insignificant cancer with PRIAS. Level of Evidence : 3 Technical Efficacy : Stage 2 J. MAGN. RESON. IMAGING 2017;45:1753–1759