Is the duration of castration resistance predictive for sequential treatment responses in the metastatic castration-resistant prostate cancer setting?

Objective Prostate cancer is the second leading cause of cancer death in men. Androgen deprivation therapy (ADT) has been the primary therapeutic approach for treatment of prostate cancer. However,nearly all patients develop the castration-resistant disease . We evaluated real-world data with abiraterone and enzalutamide treatment. By this data, we aimed to analyze whether that prior short response to ADT could predict response to subsequent therapy with androgen receptor axis targeted agent (ARATA). Material and Method We collected data from two cancer centers, 151 consecutive patients with treated abiraterone or enzalutamide in the first line of metastatic castration resistant prostat cancer (mCRPC) setting were included. The patients who received docetaxel in castration naive setting is also included. Time to castration resistance (TTCR) was defined as the duration from the initial to failure of primary ADT. Results Patients with treated ARATA were divided into two groups according to the time to castration resistance (TTCR). Patients who became resistant to ADT up to one year had a median PFS of 6.6 months, compared to median PFS of 13.3 months for patients who responded ADT for more than 1 year. (p = 0.002). In the post-docetaxel setting, median PFS is 12.6 months of patients with treated ARATA who had TTCR for more than one year, and median PFS is 6.6 months in those who had TTCR less than one year (p = 0.007).Univariate and multivariate analyses were performed to determine the clinical factors on ARATA outcomes. Eastern Cooperative Oncology Group (ECOG) performance status(PS), median prostate-specific antigen(PSA) and time to CRPC were significantly predicted outcomes of ARATA on multivariate analysis. Conclusion TTCR is also a predictor for PFS of the patients who were treated ARATA both whole cohort and post-docetaxel.