Can free PSA be used as a biomarker in biochemical recurrence after surgery to predict castrate resistant prostate cancer

177Background: PSA produced from prostate cancer (PC) cells escapes proteolytic processing, resulting in a more complexed PSA and a lower %fPSA. Higher %fpsa correlates with lower PC risk. However, the role of fPSA in biochemical recurrence (BCR) after radical prostatectomy (RP) is unknown. Methods: All patients who had BCR after RP and at least one fPSA test, were included. Patients were stratified according to the %fPSA cut-off of 0.15. Multivariable logistic regression analysis was performed to predict covariates associated with a higher %fPSA. Results: A total of 81 men with BCR were found (Table 1). Interestingly, 20% (group 1) vs. 60% (groups 2) become castrate resistant (CRPC), p<0.0001 and the time to reach CRPC state was much shorter in group 2 (33.5 months) vs. group 1 (57.9 months), p=0.05. Additionally, 60% of group 2 patients vs. 32.5% of group 1 patients developed metastasis, p=0.014. Lastly, median survival of 193 months for group 2 patients with no median survival for group 1, Log Rank tes...