Comparison of PI-RADS version 2 and PI-RADS version 2.1 for the detection of transition zone prostate cancer

Purpose: To compare the diagnostic performance of PI-RADS v2 and v2.1 for detecting transition zone prostate cancer (TZPC) on multiparametric prostate MRI (mpMRI). Method: Fifty-eight patients with elevated PSA levels underwent mpMRI at 3 T including T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI), and subsequent MRI-transrectal ultrasonography fusion-guided prostate-targeted biopsy (MRGB). The standard of reference was MRGB-derived histopathology. Two readers independently assessed each TZ lesion, assigning a score of 1-5 for T2WI, a score of 1-5 for DWI, and the overall PI-RADS assessment category according to PI-RADS v2 and v2.1. The diagnostic performance of the two methods was compared in terms of inter-reader agreement, diagnostic sensitivity, diagnostic specificity, and area under the ROC curve (AUC). Results: Of the 58 patients, 26 were diagnosed with PC (GS= 3+ 3, n= 9; GS= 3+ 4, n= 9; GS= 3+ 5, n= 1; GS= 4+ 3, n= 4; GS= 4+ 4, n= 3) and 32 with benign lesions. Regarding inter-reader agreement of overall PI-RADS assessment category, the kappa value was 0.580 for v2 and 0.645 for v2.1. For both readers, there was no difference in diagnostic sensitivity between the versions (p >= 0.500). For reader 1, the diagnostic specificity was higher for v2.1 (p= 0.002), and was similar for reader 2 (p= 1.000). For both readers, AUC tended to be higher for v2.1 than for v2, but the difference was not significant (0.786 vs. 0.847 for reader 1, p= 0.052; and 0.808 vs. 0.858 for reader 2, p= 0.197). Conclusions: These results suggest that compared with PI-RADS v2, PI-RADS v2.1 could be preferable for evaluating TZ lesions.