Interobserver Reproducibility of the PI-RADS Version 2 Lexicon: A Multicenter Study of Six Experienced Prostate Radiologists

Abstract

Purpose:To determine the interobserver reproducibility of the Prostate Imaging Reporting and Data System (PI-RADS) version 2 lexicon. Materials and Methods:This retrospective HIPAA-compliant study was institutional review board-approved. Six radiologists from six separate institutions, all experienced in prostate magnetic resonance (MR) imaging, assessed prostate MR imaging examinations performed at a single center by using the PI-RADS lexicon. Readers were provided screen captures that denoted the location of one specific lesion per case. Analysis entailed two sessions (40 and 80 examinations per session) and an intersession training period for individualized feedback and group discussion. Percent agreement (fraction of pairwise reader combinations with concordant readings) was compared between sessions. k coefficients were computed. Results:No substantial difference in interobserver agreement was observed between sessions, and the sessions were subsequently pooled. Agreement for PI-RADS score of 4 or greater was 0.593 in peripheral zone (PZ) and 0.509 in transition zone (TZ). In PZ, reproducibility was moderate to substantial for features related to diffusion-weighted imaging (k = 0.535-0.619); fair to moderate for features related to dynamic contrast material-enhanced (DCE) imaging (k = 0.266-0.439); and fair for definite extraprostatic extension on T2-weighted images (k = 0.289). In TZ, reproducibility for features related to lesion texture and margins on T2-weighted images ranged from 0.136 (moderately hypointense) to 0.529 (encapsulation). Among 63 lesions that underwent targeted biopsy, classification as PI-RADS score of 4 or greater by a majority of readers yielded tumor with a Gleason score of 3+4 or greater in 45.9% (17 of 37), without missing any tumor with a Gleason score of 3+4 or greater. Conclusion:Experienced radiologists achieved moderate reproducibility for PI-RADS version 2, and neither required nor benefitted from a training session. Agreement tended to be better in PZ than TZ, although was weak for DCE in PZ. The findings may help guide future PI-RADS lexicon updates.q RSNA, 2016

Risk Stratification Among Men With Prostate Imaging Reporting and Data System version 2 Category 3 Transition Zone Lesions: Is Biopsy Always Necessary?

“…All of the studies were performed at a single institution, so the ADC threshold reported herein, which included a b value of 0 s/mm 2 in its calculation, may not be directly applicable to different scanners and platforms or calculations that do not include b values below 100 s/mm 2 . The clinically significant PCA detection rate of 15% among PI-RADSv2 category 3 TZ lesions in our cohort is slightly higher than that reported in previous publications [2, 3, 6] and could reflect enrichment of TZ lesions, given that they are more often occult at systematic biopsy and that nearly a quarter of our population had undergone at least one prior negative systematic biopsy. Last, although suggested by PI-RADSv2, the definition of clinically significant PCA that we used in this study (Gleason score ≥ 3 + 4) may not be universally agreed on because it does not account for tumor volume and is based on targeted biopsy rather than radical prostatectomy.…”

“…In a multireader reproducibility study of PI-RADSv2, Rosenkrantz et al [6] reported an overall PCA detection rate of 15.4% among lesions with overall PI-RADSv2 category of less than 4, none of which was clinically significant PCA. Tan et al [3] reported an overall PCA detection rate of 19.4% among PI-RADSv2 category 3 lesions, less than 10% of which constituted clinically significant PCA.…”

“…Given the low likelihood of clinically significant PCA in PI-RADSv2 category 3 lesions, especially lesions in the TZ, where interreader agreement and positive predictive value are lower [6, 13], we sought to identify ancillary clinical and imaging features that might improve risk stratification in this subset of patients. We observed that the combination of both PSAD of 0.15 ng/mL 2 or greater and lesion ADC of less than 1000 mm 2 /s significantly increased the likelihood of clinically significant PCA in our cohort.…”

Predictive Parameters Identifying Men Eligible for a Sole MRI/Ultrasound Fusion-Guided Targeted Biopsy without an Additional Systematic Biopsy

“…Applying the lesion size for patient selection suitable to a TB-only approach would have led to a great reduction of biopsy cores while only posing a small risk to miss tumours or underestimating the PCa risk group. Considering the reader variability of the mpMRI rating of 40% and the possible pitfalls of MRI/US fusion biopsies, the lesion size may present a valid predictor for a TB-only approach [25,26] . The combination of the predictive factors would have further reduced the number of tumors missed or underestimated.…”

The Director of Prostate Imaging: advancing care for prostate cancer patients

“…The PI-RADS v2 guidelines were developed to address this issue [3]. Nonetheless, studies show moderate inter-reader variability of PI-RADS v2 [4,5]. It is thus important to have systems in place to attempt to minimize the problem.…”