Standardized Reporting of Prostate MRI: Comparison of the Prostate Imaging Reporting and Data System (PI-RADS) Version 1 and Version 2

Introduction Objective of our study was to determine the agreement between version 1 (v1) and v2 of the Prostate Imaging Reporting and Data System (PI-RADS) for evaluation of multiparametric prostate MRI (mpMRI) and to compare their diagnostic accuracy, their inter-observer agreement and practicability. Material and Methods mpMRI including T2-weighted imaging, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced imaging (DCE) of 54 consecutive patients, who subsequently underwent MRI-guided in-bore biopsy were re-analyzed according to PI-RADS v1 and v2 by two independent readers. Diagnostic accuracy for detection of prostate cancer (PCa) was assessed using ROC-curve analysis. Agreement between PI-RADS versions and observers was calculated and the time needed for scoring was determined. Results MRI-guided biopsy revealed PCa in 31 patients. Diagnostic accuracy for detection of PCa was equivalent with both PI-RADS versions for reader 1 with sensitivities and specificities of 84%/91% (AUC = 0.91 95% CI[0.8-1]) for PI-RADS v1 and 100%/74% (AUC = 0.92 95% CI[0.8-1]) for PI-RADS v2. Reader 2 achieved similar diagnostic accuracy with sensitivity and specificity of 74%/91% (AUC = 0.88 95% CI[0.8-1]) for PI-RADS v1 and 81%/91% (AUC = 0.91 95% CI[0.8-1]) for PI-RADS v2. Agreement between scores determined with different PI-RADS versions was good (reader 1: kappa = 0.62, reader 2: kappa = 0.64). Inter-observer agreement was moderate with PI-RADS v2 (kappa = 0.56) and fair with v1 (kappa = 0.39). The time required for building the PI-RADS score was significantly lower with PI-RADS v2 compared to v1 ( 24.7 +/- 2.3 s vs. 41.9 +/- 2.6 s, p<0.001). Conclusion Agreement between PI-RADS versions was high and both versions revealed high diagnostic accuracy for detection of PCa. Due to better inter-observer agreement for malignant lesions and less time demand, the new PI-RADS version could be more practicable for clinical routine.