Serum isoform [-2]proPSA derivatives significantly improve prediction of prostate cancer at initial biopsy in a total PSA range of 2-10 ng/ml: a multicentric European study

Background: Strategies to reduce prostate-specific antigen (PSA)-driven prostate cancer (PCa) overdiagnosis and overtreatment seem to be necessary.

Objective: To test the accuracy of serum isoform [-2]proPSA (p2PSA) and its derivatives, percentage of p2PSA to free PSA (fPSA; %p2PSA) and the Prostate Health Index (PHI)-called index tests-in discriminating between patients with and without PCa.

Design, setting, and participants: This was an observational, prospective cohort study of patients from five European urologic centers with a total PSA (tPSA) range of 2-10 ng/ml who were subjected to initial prostate biopsy for suspected PCa.

Outcome measurements and statistical analysis: The primary end point was to evaluate the specificity, sensitivity, and diagnostic accuracy of index tests in determining the presence of PCa at prostate biopsy in comparison to tPSA, fPSA, and percentage of fPSA to tPSA (%fPSA) (standard tests) and the number of prostate biopsies that could be spared using these tests. Multivariable logistic regression models were complemented by predictive accuracy analysis and decision curve analysis.

Results and limitations: Of >646 patients, PCa was diagnosed in 264 (40.1%). Median tPSA (5.7 vs 5.8 ng/ml; p=0.942) and p2PSA (15.0 vs 14.7 pg/ml) did not differ between groups; conversely, median fPSA (0.7 vs 1 ng/ml; p<0.001), %fPSA (0.14 vs 0.17; p<0.001), %p2PSA (2.1 vs 1.6; p<0.001), and PHI (48.2 vs 38; p<0.001) did differ significantly between men with and without PCa. In multivariable logistic regression models, p2PSA, %p2PSA, and PHI significantly increased the accuracy of the base multivariable model by 6.4%, 5.6%, and 6.4%, respectively (all p<0.001). At a PHI cut-off of 27.6, a total of 100 (15.5%) biopsies could have been avoided. The main limitation is that cases were selected on the basis of their initial tPSA values.

Conclusions: In patients with a tPSA range of 2-10 ng/ml, %p2PSA and PHI are the strongest predictors of PCa at initial biopsy and are significantly more accurate than tPSA and %fPSA.