Validation of dominant and secondary sequence utilization in PI-RADS v2 for classifying prostatic lesions.

Introduction: To assess the secondary sequence rule in The Prostate Imaging Reporting Data System (PI-RADS) version 2 by comparing the detection of Grade group 1+ (GG1+) and 2+ (GG2+) cancers in PI-RADS 3, an upgraded PI-RADS 4, and true (non-upgraded) PI-RADS 4 targets. Materials and

Methods: We analyzed a total of 589 lesions scored as PI-RADS 3 or 4 obtained from 434 men who underwent mpMRI-US fusion biopsy from September 2015 to November 2017 for evaluation of GG1+ and GG2+ prostate cancer. PI-RADS 4 lesions were differentiated into those that were 'upgraded' to PI-RADS 4 based on the secondary sequence and those that were 'true' PI-RADS 4 based on the dominant sequence.

Results: The odds of detecting a GG2+ cancer was significantly higher for an upgraded 4 (peripheral zone (PZ): OR 5.06, 95%CI 2.04-12.54, p < 0.001, transitional zone (TZ): OR 3.08, 95%CI 1.04-9.08, p = 0.042) and true 4 (PZ: OR 5.82, 95%CI 3.10-10.94, p < 0.0001, TZ: OR 2.43, 95%CI 1.14-5.18, p = 0.022) lesions compared to PI-RADS 3 lesions. Additionally, we found no difference in the odds of detecting a GG2+ prostate cancer between a true PI-RADS 4 (OR 1.15, 95%CI 0.49-2.71 p = 0.746) and upgraded 4 (referent) in the PZ. Similar non-significance was noted between true 4 (OR 0.79, 95%CI 0.26-2.38 p = 0.674) and upgraded 4 lesions in the TZ for detection of GG2+ cancers.

Conclusions: Upgraded PI-RADS 4 and true 4 targets have a higher odds of detecting GG1+ and GG2+ compared to PI-RADS 3 in the PZ and TZ. Our findings validate the revised scoring system for PI-RADS.