Evaluating the impact of reader experience on PI-RADS 3 of version 2.1 scoring concordance in multiparametric prostate MRI: a single-center analysis.

PURPOSE: PI-RADS 3 lesions remain a "grey-zone" with an equivocal category on prostate mpMRI, complicating biopsy decisions and treatment strategies. This study aimed to investigate how radiologist experience affects the interpretation of prostate multiparametric magnetic resonance imaging (mpMRI) with Prostate Imaging Reporting and Data System (PI-RADS) score 3 of version 2.1.

METHODS

A retrospective study involved three radiologists of different experience levels independently evaluating mpMRI images with PI-RADS 3 scores and confirmed pathological outcomes. From January 2023 to April 2025, 673 patient cases were reviewed. Excluding cases with prior interventions, non-PI-RADS 3 scores, or lacking pathological confirmation, 133 patients were analyzed. Inter-reader reliability was assessed using Cohen's kappa statistic (k), and correlations between PI-RADS and Gleason scores were analyzed with Kendall's tau (t). Diagnostic performance metrics including the area under the ROC curve (AUC), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated.

RESULTS

Median k score among all radiologist pairs was 0.149. The correlation between PI-RADS and Gleason scores was weakly positive but not statistically significant (t = 0.197). Senior Reader 2 demonstrated the highest AUC (0.748), accuracy (63.2%), PPV (48.2%), NPV (88.0%), and sensitivity (86.97%). Expert Reader 1 had the highest specificity (56.3%).

CONCLUSION

Three assigned radiologists with different experience levels achieved generally poor inter‑reader agreement using the PI‑RADS version 2.1 guideline, and varying expertise did not significantly influence PI-RADS 3 evaluations. Future work should refine interpretation flows, adjunct decision rules, test weighted agreement statistics, and validate these findings in larger, multicenter cohorts.