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

ABSTRACT  Objective: To evaluate the efficacy and safety of enzalutamide in metastatic castration-resistant prostate cancer (mCRPC) in docetaxel-naive and docetaxel-pretreated patients. Observational study. HSU Dr. Abdurrahman Yurtaslan Oncology Training and Research Hospital, Department of Medical Oncology, Ankara, Turkey, from March 2017 to July 2019. 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. 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. PSA response, radiological response and duration of enzalutamide treatment may predict the improvement of survival in patients with mCRPC treated with enzalutamide.   Key Words: Enzalutamide, Docetaxel, Castration-resistant prostate cancer, Overall survival, Progression-free survival.