Enzalutamide Treatment in Metastatic Castration-resistant Prostate Cancer: Before and after Docetaxel

Objective: To evaluate the efficacy and safety of enzalutamide in metastatic castration-resistant prostate cancer (mCRPC) in docetaxel-naive and docetaxel-pretreated patients. Study Design: Observational study. Place and Duration of Study: HSU Dr. Abdurrahman Yurtaslan Oncology Training and Research Hospital, Department of Medical Oncology, Ankara, Turkey, from March 2017 to July 2019. Methodology: A total of 67 patients with mCRPC were retrospectively evaluated. Castration-naive patients and non-metastatic patients were excluded from the study. Comorbid diseases, ECOG performance status, PSA response, and the radiological response of the patients were recorded. Kaplan-Meier method was used for survival analysis, and a Cox regression model was formed. Results: The overall survival (OS) was significantly longer in patients with eastern cooperative oncology group performance status (ECOG PS) 0 (26.0 vs. 14.0 months, p=0.031), PSA response (26.0 vs. 7.0 months, p=0.002), radiological response (26.0 vs. 10.0 months, p=0.006) and duration of enzalutamide >= 9 months (26.0 vs. 7.0 months, p<0.001) compared to ECOG PS 1. According to Cox regression analysis, patients with PSA response had 0.35 fold (CI.95% 0.13-0.94) reduced the risk of death and 0.36-fold (CI.95%0.16-0.85) reduced the risk of progression compared to those without PSA response. Moreover, longer enzalutamide treatment (>= 9 months) was noted to decrease the risk of death. Conclusion: PSA response, radiological response and duration of enzalutamide treatment may predict the improvement of survival in patients with mCRPC treated with enzalutamide.