Accuracy and Interobserver Agreement for Prostate Imaging Reporting and Data System, Version 2, for the Characterization of Lesions Identified on Multiparametric MRI of the Prostate

Objective: The objective of this study was to measure the accuracy and interobserver agreement of the Prostate Imaging Reporting and Data System, version 2 (PI-RADSv2), for the characterization of prostate lesions on multiparametric MRI.

Materials and methods: This retrospective study included 170 men examined at a single institution between August 2014 and February 2015 on a 3-T MRI scanner. Study patients were found to have lesions concerning for prostate cancer that were targeted for MRI/transrectal ultrasound fusion biopsy. Two experienced readers independently assigned a PI-RADSv2 assessment category to the dominant lesion in each patient. The AUC was calculated to determine reader accuracy for the detection of clinically significant prostate cancer (Gleason score ≥ 3 + 4). The Cohen kappa statistic was used to quantify interobserver agreement.

Results: The prevalence of clinically significant prostate cancer was 0.36 (61/170 patients). The AUCs for readers 1 and 2 were 0.871 and 0.882, respectively. The AUCs were greater for peripheral zone lesions than for transition zone lesions. When a PI-RADSv2 assessment category ≥ 3 was considered positive, the agreement between readers was good overall (κ = 0.63) and was fair for transition zone lesions (κ = 0.53). When a PI-RADSv2 assessment category ≥ 4 was considered positive, the agreement was excellent overall (κ = 0.91) and was excellent for both peripheral zone lesions (κ = 0.91) and transition zone lesions (κ = 0.87).

Conclusion: Two experienced readers were able to accurately identify patients with clinically significant prostate cancer using PI-RADSv2 with good interobserver agreement overall.