A High Percent Free Prostate Specific Antigen in the Setting of Biochemical Recurrence after Radical Prostatectomy is Associated with Poorer Outcomes: A Validation Study Using Prospectively Collected Biobank Specimens.

ABSTRACT

PURPOSE: The role of percent free prostate specific antigen (%fPSA) in patients who have undergone radical prostatectomy and subsequently experienced disease relapse is unclear. We previously conducted 2 retrospective studies and found %fPSA 15 or greater in the setting of biochemical recurrence confers more aggressive disease. To validate that finding we used biobank specimens collected prospectively when patients were first diagnosed with biochemical recurrence. MATERIALS AND METHODS: Biobank specimens of patients with undetectable prostate specific antigen after radical prostatectomy and subsequent biochemical recurrence (prostate specific antigen 0.1 ng/ml or greater) were analyzed for %fPSA. Patients were stratified according to the %fPSA cutoff of 15. Univariable and multivariable logistic regression analysis was performed to predict covariates associated with a higher %fPSA. Cox proportional hazard models were performed to evaluate the prognostic effect of %fPSA on androgen deprivation therapy-free survival, metastasis-free survival, castration resistant-free survival and cancer specific survival. RESULTS: A total of 154 men were included in the study, of whom 126 (82%) had %fPSA less than 15 and 28 (18%) had %fPSA 15 or greater. Median followup for %fPSA less than 15 and %fPSA 15 or greater was 75 and 69 months, respectively. Patients with %fPSA 15 or greater had increased hazard of receiving androgen deprivation therapy (43% vs 25%, adjusted HR 2.40, 95% CI 1.12-5.11), metastatic disease (21% vs 7.9%, adjusted HR 4.10, 95% CI 1.11-15.2) and castration resistant prostate cancer (14% vs 4.0%, unadjusted HR 4.14, 95% CI 1.11-15.5) vs %fPSA less than 15, respectively. CONCLUSIONS: Patients with %fPSA 15 or greater were started on androgen deprivation therapy earlier, and they had progression to castration resistant prostate cancer and metastatic stage earlier. %fPSA 15 or greater in the setting of biochemical recurrence after radical prostatectomy is an indicator of a more aggressive disease. Unlike in the diagnostic setting, a higher %fPSA portends a worse clinical outcome.