The prostate cancer gene 3 (PCA3) urine test in men with previous negative biopsies: does free-to-total prostate-specific antigen ratio influence the performance of the PCA3 score in predicting positive biopsies?

OBJECTIVE: to determine the performance characteristics of the prostate cancer gene 3 (PCA3) score on the outcome of biopsy relative to different ranges of free-to-total prostate-specific antigen (PSA) ratio (f/tPSA) in men with a previous negative biopsy and a PSA level of 2.5-10 ng/mL, as urine tests like PCA3 are currently under investigation in order to improve prostate cancer diagnosis and to decrease the rate of unnecessary rebiopsies.

PATIENTS AND METHODS: data from the previous prospective European multicentre study were reviewed. Only patients with a PSA level of 2.5-10 ng/mL were included in the present study. In all, 301 patients had complete data. The diagnostic accuracy of the PCA3 score for predicting a positive biopsy outcome was studied using sensitivity, specificity, negative and positive predictive values. The PCA3 performance was evaluated relative to three different subgroups of f/tPSA, as follows: >20% (group 1), 10-20% (group 2) and <10% (group 3).

RESULTS: the prostate cancer detection rates were 18.8%, 23.9% and 34.8% in groups 1, 2 and 3, respectively. The area under the receiver operating characteristic curve of the PCA3 score, total PSA and f/tPSA was 0.688, 0.553 and 0.571, respectively. The percentage of men with positive biopsies was 30.6%, 37.0% and 44.4% in those with a PCA3 score of >30, vs 10.3%, 15.5% and 28.6% when the PCA3 score was <30, in groups 1, 2 and 3, respectively. The difference was significant only in groups 1 and 2. In men with a f/tPSA of ≤ 10% the difference in detection rates relative to the PCA3 score was not statistically significant regardless of which PCA3 threshold was used. A high PCA3 score was significantly associated with age, clinical T2 stage and positive biopsy (P < 0.001, 0.013 and <0.001, respectively). In bivariate analysis accounting for the PCA3 score and the f/tPSA, a PCA3 score of >30 was a significant independent predictor of positive biopsies (odds ratio 3.01; 95% confidence interval 1.74-5.23; P < 0.001).

CONCLUSIONS: PCA3 remained a better predictor of prostate cancer than f/tPSA. In men with a f/tPSA of >10%, the use of the PCA3 score was highly correlated with the risk of having cancer on re-biopsy, and could prevent unnecessary prostate biopsies if the value is low.