Background: Enzalutamide is an oral androgen-receptor inhibitor that prolongs survival in men with castration-resistant prostate cancer (CRPC) in whom the disease has progressed after androgen-deprivation therapy. We investigated oncological outcomes and clinicopathological factors related to overall survival in chemotherapy-naïve patients with CRPC who received enzalutamide treatment.
Methods: Seventy-seven CRPC patients who received enzalutamide treatment before chemotherapy were retrospectively assessed. Factors associated with overall survival after enzalutamide administration were analyzed.
Results: The median age at the time of treatment was 76 years old (range, 55 to 95). Initial PSA before enzalutamide treatment was a median of 7.16 ng/ml (range, 0.17 to 2081.86). Bone, lymph node, and visceral metastasis were observed in 64.3%, 31.4% and 2.9%, respectively. Four weeks after initiation of the treatment, 30%, 50% and 70% of PSA decrease were observed in 56.9%, 47.2% and 30.6% of patients, respectively. After enzalutamide treatment, abiraterone, docetaxel and cabazitaxel were administered in 40.3%, 35.1% and 14.3%, respectively. Overall survival was significantly associated with existence of bone metastasis and base-line PSA at the time of enzalutamide treatment and any PSA decrease less than base-line at the 4 weeks after initiation of the treatment. Any PSA decrease at the time of 4 weeks after initiation of the treatment was an independent prognostic factor that was associated with overall survival. Nineteen patients died of the disease with a median follow-up period of 16 months (range, 1 to 44).
Conclusion: PSA decrease less than base-line at the 4 weeks after introduction of enzalutamide in chemotherapy-naïve patients with CRPC could be important to have a better outcome.