Transition zone-based prostate-specific antigen density for differentiating clinically significant prostate cancer in PI-RADS score 3 lesions.

We intended to investigate the potential of several transitional zone (TZ) volume-related variables for the detection of clinically significant prostate cancer (csPCa) among lesions scored as Prostate Imaging Reporting and Data System (PI-RADS) category 3. Between September 2018 and August 2023, patients who underwent mpMRI examination and scored as PI-RADS 3 were queried from our institution. The diagnostic performances of prostate-specific antigen density (PSAD), TZ-adjusted PSAD (TZPSAD), and TZ-ratio (TZ volume/whole gland prostate volume) were analyzed. We calculated the sensitivity and specificity for each variable, the overall accuracy was evaluated with the area under the receiver operating characteristic curve (AUC). The best cutoff value was determined by the Youden index, and differences between diagnostic performances were compared with the Delong test. A total of 154 TZ lesions were included, of them 28 were diagnosed with csPCa. The AUC for PSAD, TZPSAD, and TZ-ratio were 0.644 (95% CI 0.538-0.751), 0.714 (95% CI 0.607-0.821), and 0.746 (95% CI 0.636-0.856), with corresponding optimal cutoff values of 0.11 ng/ml/ml, 0.21 ng/ml/ml, and 0.66 ng/ml/ml, respectively. PSAD was significantly inferior to either TZPSAD (P = 0.03) or TZ-ratio (P = 0.03). The combination model including TZPSAD, TZ-ratio, and age generated an AUC of 0.838 (95% CI 0.759-0.917), significantly higher than use of these variables alone, with P values of 0.001 and 0.035 for the TZPSAD and TZ-ratio, respectively. TZPSAD and TZ-ratio were found to be independent predictors for differentiating csPCa among TZ lesions categorized as PI-RADS score 3. Furthermore, by combining these two variables with others, the diagnostic performance can be improved significantly.