Comparison of Diagnostic Performance of PI-RADS V2 and V2.1 and Interobserver Agreement in Both Versions

Objective: To compare the diagnostic performance for the detection of clinically significant prostate cancers and interobserver agreement between PI-RADS v2 and v2.1 Material and Method: The mpMRI images of 258 patients and 394 nodüles included in this retrospective study were obtained on 3T MR and evaluated by two radiologists according to PI-RADS v2 and v2.1. Sensitivity and specificity between v2 and v2.1 compared. Detection rates for clinically significant prostate cancers of upgraded and downgraded lesions in the use of v2.1 from v2 were assessed. Interobserver agreement was assessed using κ statistics. Results: PI-RADS v2.1 and v2 showed higher sensitivity and lower specificity (100%, 52.38%) in peripheral zone and showed higher sensitivity and specificity (92.86%, 98.79%) in transition zone for category ≥4 lesions in the detection of csPCa, not significantly difference was found between the two versions. Interobserver agreement was statistically significant and very weak in the transition zone (κ=0.383, κ=0.279, respectively), very strong in the peripheral zone (κ=0.869) according to both classifications and they were similar. Conclusion: The diagnostic performance of PI-RADS v2 and v2.1 were found similar in detecting clinically significant cancers and all cancers in both zones. The clinically significant cancer detection rate in category 2+1 lesions in the transition zone was higher than in category 2 lesions but it wasn’t statistically significant. Interobserver agreement was low in the transition zone and very strong in the peripheral zone in both versions.