[Implications of PI-RADS Version 1 and Updated Version 2 on the Scoring of Prostatic Lesions in Multiparametric MRI]

A revised version of the PI-RADS scoring system has been introduced and score-related variability between version 1 and 2 may be suspected. This study aimed to assess the PI-RADS scores derived from version 1 (v1) and the updated version 2 (v2).

61 patients with biopsy-proven prostate cancer (PCa) and 90 lesions detected on pre-biopsy 3-Tesla multiparametric MRI were included in this retrospective analysis. 2 experienced radiologists scored all lesions in consensus. Lesion scores differing between PI-RADS v1 and v2 were further analyzed. Histology data from radical prostatectomy (RP) were included when available.

The PI-RADS v1 and v2 score differed in 52% of patients (32/61) and in 39% of lesions (35/90). On a lesion basis, the reason for the differences were related to sum score in v1 vs. categorical system in v2 in 51% (18/35) of lesions, cutoff between PI-RADS 4 and 5 based on lesion size in v2 as opposed to the sum score in v1 in 31% (11/35) and were inconclusive in 17% (6/35). The RP subgroup indicates enhanced detection of PCas with GS 3+3 and GS 3+4 in v2.

PI-RADS scores of prostatic lesions frequently differed between v1 and v2, the major reasons for these differences being score-related. In men undergoing RP, PI-RADS v2 improved detection of low risk PCa, but did not increase accuracy for discrimination of GS 3+4 vs. GS≥4+3 compared to v1. Urologists should be aware of the system-related differences when interpreting PI-RADS scores.