The purpose of this study was to evaluate the prognostic ability of early changes of total prostate specific antigen (tPSA), free PSA (fPSA), [-2]proPSA and the Prostate Health Index (PHI) following initiation of Abiraterone-therapy in men with castration resistant prostate cancer (mCRPC). In 25 patients, PSA-subforms were analyzed before and at 8-12 weeks under therapy as prognosticators of progression-free-survival (PFS) and overall survival (OS). Comparing patients with a PFS < vs. ≥12 months by using Mann-Whitney-Wilcoxon Tests, the relative-median-change of tPSA (-0.1% vs. -86.8%; p = 0.02), fPSA (12.1% vs. -55.3%; p = 0.03) and [-2]proPSA (8.1% vs. -59.3%; p = 0.05) differed significantly. For men with ≤ vs. >15 months of OS there was a non-significant trend for a difference in the relative-median-change of fPSA (17.0% vs. -46.3%; p = 0.06). In Kaplan-Meier analyses, declining fPSA and [-2]proPSA were associated with a longer median PFS (13 months, 95% confidence interval (CI): 9.6-16.4 vs. 10 months, 95% CI: 3.5-16.5; p = 0.11), respectively. Correspondingly, decreasing fPSA and [-2]proPSA values indicated an OS of 32 months (95% CI: not reached (NR)) compared to 21 months in men with rising values (95% CI: 7.7-34.3; p = 0.14), respectively. We concluded that the addition of fPSA- and [-2]proPSA-changes to tPSA-information might be further studied as potential markers of early Abiraterone response in mCRPC patients.
Keywords: PHI; [−2]proPSA; abiraterone acetate; fPSA; mCRPC; prognosticators; prostate cancer; surrogate biomarker; tPSA.