Introduction:
Transition zone (TZ) prostate cancer poses diagnostic challenges due to overlapping imaging features with benign prostatic hyperplasia (BPH). The study aims to investigate whether Prostate Imaging Reporting and Data System (PI-RADS) v2.1 combined with prostate-specific antigen density (PSAD) can enhance diagnostic accuracy in distinguishing TZ cancer from BPH.

Material and methods:
The retrospective study included 377 patients divided into two groups: TZ cancer group (n = 139) and BPH group (n = 238). Two radiologists independently reviewed prostate MR images of each patient and assigned a PI-RADS score for the TZ lesion. Clinical characteristics between the two groups were compared using Chi-square test, t-test or Mann-Whitney U-test. The diagnostic performance of PI-RADS scores, PSAD and the combined parameters was determined by ROC curve analysis.

Results:
Statistically significant differences were found in PSA, prostate volume, PSAD and PI-RADS scores between the two groups (All P  0.0001). No difference in age was observed between the two groups (P = 0.602). The area under the curve (AUC) for PI-RADS v2.1 alone was 0.802 (95% CI: 0.759-0.841) with a sensitivity of 79.14% and specificity of 74.37% at a cutoff of  4. The AUC for PSAD alone was 0.808 (95% CI: 0.765-0.847) with a sensitivity of 79.14% and specificity of 77.31% at a cutoff of 0.22 ng/mL/mL. Combining PI-RADS and PSAD yielded an AUC of 0.873 (95% CI: 0.835-0.905), with a sensitivity of 79.26% and specificity of 86.55%.

Conclusions:
The combination of PI-RADS v2.1 and PSAD enhances the diagnostic accuracy for TZ cancer, thereby reducing unnecessary invasive procedure.