Predictive factors for response to abiraterone in metaststic castration refractory prostate cancer

Background: Management of metastatic castration refractory prostate cancer (CRPC) is rapidly evolving. Rationalisation of treatment requires identification of those patients more likely to benefit from a particular therapy. We reviewed the outcome of patients treated with abiraterone at our Institution to describe factors predictive for response. Patients and Methods: Patients with CRCP treated with abiraterone were identified. Baseline variables and potential prognostic factors were extracted from electronic records. Outcome measures included overall survival (OS), prostate-specific antigen (PSA) response and time to PSA progression (TTPP). The Kaplan–Meier method and Cox proportional hazards model were used to analyze survival data. Results: A total of 61 patients met the inclusion criteria. In multivariate analysis, three independent predictors of OS were identified: Duration of response to androgen deprivation therapy (ADT) (hazard ratio(HR)=0.95, p=0.006), performance status (HR=7.4, p=0.013), and baseline haemoglobin (HR=0.47, p≤0.001). Conclusion: This study has identified three factors predictive for response to abiraterone in CRPC. Duration of response to ADT has not been previously shown to be a predictive factor for patients with CRCP. We suggest that a prospective validation is required.