The utility of the transition zone index for optimal predictor selection of prostate cancer in patients with intermediate PSA levels

Objective To investigate the utility of the transition zone index (TZI) for optimal predictor selection of prostate cancer (PCa) in patients with prostate-specific antigen (PSA) levels of 4 to 10 ng/ml. Methods In this retrospective cohort study, results of transrectal ultrasonography (TRUS)-guided biopsy were assessed in 616 consecutive patients; The prostate and transition zone volumes were determined by TRUS. A TZI cutoff value of 0.47 produced the best sensibility and specificity rates in receiver operating characteristic (ROC) curve analysis and thus was used to classify the study subjects into group TZI ≤0.47 and group TZI ≤0.47. Logistic regression analysis was used to predict outcomes. The variables that were statistically significant in the stepwise logistic regression analysis were assessed using the ROC curve and the area under the curve (AUC). Results Overall, 166 of the 616 patients (26.9%) had histologically confirmed PCa. A total of 238 (38.6%) patients were classified into group TZI ≤0.47, of whom 97 (40.8%) exhibited a positive biopsy, and 378 (61.4%) patients were classified into group TZI>0.47, of whom 69 (18.3%) exhibited a positive biopsy. The stepwise logistic regression analysis revealed that PSA density (PSAD) exhibited the strongest predictive value in the overall population and in group TZI ≤0.47, whereas PSA transition zone density (PSATZD) was the optimal predictor in group TZI>0.47. The ROC curve analysis revealed that when using the TZI- specific 100% sensitivity cutoffs, 17.7% and 25% of the biopsies were unnecessary and could be avoided in the overall patient population prior to and following the division into groups, respectively (P = 0.002). Using an individually generated 95% sensitivity cutoff of 0.12 ng/ml 2 for PSAD and a cutoff of 0.179 ng/ml 2 for PSATZD for TZI-stratified cohorts of TZI ≤ 0.47 and TZI>0.47, a more consistent specificity of 44% and 46.9%, respectively, for each cohort was observed. Conclusion The optimal predictor for PCa differs between various TZI levels. The combination of PSAD in patients with TZI≤0.47 and PSATZD in patients with TZI>0.47 helps to identify potentially unnecessary biopsies compared to the use of a single PSAD for the entire patient population.