Enzalutamide effective in chemo-naïve men with metastatic castration-resistant prostate cancer
The use of oral androgen receptor inhibitor enzalutamide may benefit chemotherapy-naïve patients with metastatic castration-resistant prostate cancer and low baseline prostate specific antigen irrespective of disease burden, signifying that targeting the androgen receptor signalling pathway is a therapeutic option in similar patients, suggests a recent study.
The investigators analysed outcomes in patients with low prostate specific antigen and a high disease burden who were given enzalutamide in the Safety and Efficacy Study of Oral MDV3100 in Chemotherapy-Naive Patients with Progressive Metastatic Prostate Cancer (PREVAIL) study.
Patients were stratified posthoc by high volume disease, defined as >4 bone metastases and/or visceral disease, and by low volume disease, defined as ≤4 bone metastases with no visceral disease. Posthoc analyses included radiographic progression-free and overall survival in the once-daily enzalutamide and placebo arms. Low baseline prostate specific antigen was defined as <10 ng/ml.
A total of 1,717 men were enrolled in PREVAIL, of which 242 (14.1 percent) had low baseline prostate specific antigen, including 110 with high volume disease.
Patients in the enzalutamide group had reduced risk of radiographic progression compared with those in the placebo group (hazard ratio [HR], 0.20; 95 percent CI, 01.0 to 0.42). This decrease occurred regardless of tumour burden (high volume disease HR, 0.17; 0.06 to 0.51; low volume disease HR, 0.25; 0.09 to 0.70).
Median overall survival was not reached in patients with low baseline prostate specific antigen in either the enzalutamide or placebo arm.
“Metastatic castration-resistant prostate cancer with low baseline prostate specific antigen represents an early stage in the natural history of castration resistant prostate cancer progression (low volume disease), low prostate specific antigen producing disease or disease that is less dependent on androgen receptor biology (high volume disease),” researchers said.