Analysis of prognostic biomarkers of response in patients with metastatic castration-resistant prostate cancer treated with abiraterone: A. C. Camargo Cancer Center experience

335 Background: Despite therapeutic progress in the management of advanced prostate cancer during the past decade, metastatic castration-resistant prostate cancer (mCRPC) remains a disease that causes substantial morbidity and mortality worldwide. A greater understanding of biomarkers permits to guide personalized therapy and can inform clinical trials tailored to men most likely to derive benefit from a given therapy. We aimed to identify prognostic biomarker candidates of Abiraterone Acetate (AA) response in mCRPC patients. Methods: A retrospective clinical records analysis of mCRPC patients treated with AA at A. C. Camargo Cancer Center between January 2012 to December 2016 was realized. Baseline clinical parameters evaluated were: Age, ECOG performance status, metastatic disease at diagnosis, Gleason score, prostate-specific antigen (PSA), Neuroendocrine differentiation, duration of previous androgen-deprivation therapy (ADT), PSA doubling-time (PSAdt), Timing of AA (chemotherapy-naïve or not), PSA response and alkaline phosphatase (ALP) level. Data were analyzed in relation to progression free survival (PFS) stratified by each parameter. Results: We included 141 patients with mCRPC treated with AA to correlate prognostic biomarkers with PFS. Five risk factors individually were associated with poor prognosis and a high risk to progression during AA therapy and were included in the final model: ECOG ≥2 [Relative risk (RR) = 1.52]; PSAdt < 3 months (RR = 2.7); PSA response ( < 50% decline) (RR = 3.03); AA post docetaxel (RR = 1.63) and duration of previous ADT < 12 months (RR = 1.52). The probability to progression free survival in patients receiving AA calculated in 1, 2 and 3 years, was 39,2%, 15,2% and 6,2%, respectively. Conclusions: This analysis identified five factors used to model survival in mCRPC patients treat with AA in our institutional series. Whereas no biomarker has been validated as a predictor of response to a therapy in mCRPC, these those potential clinical biomarkers may help clinicians in distinguishing patients with mCRPC who would obtain the best survival benefit from AA treatment.