The TERRAIN trial included 375 patients with asymptomatic or minimally symptomatic metastatic CRPC who were randomly assigned to take enzalutamide or bicalutamide. Men in the enzalutamide group had significantly improved progression-free survival (median 15.7 months vs. 5.8 months).
Xtandi (enzalutamide) is an oral androgen receptor inhibitor that improves survival in men with metastatic castration-resistant prostate cancer (CRPC) before and after chemotherapy. Bicalutamide is a nonsteroidal antiandrogen widely used to treat men with nonmetastatic or metastatic CRPC.
The STRIVE trial included men with either nonmetastatic (139 men) or metastatic (257 men) CRPC who were randomly assigned to take enzalutamide or bicalutamide. The study found that enzalutamide reduced the risk of disease progression or death by 76% compared to bicalutamide. The median time to progression free survival was 19.4 months with enzalutamide vs. 5.7 months with bicalutamide.
In both the studies, men continued with androgen deprivation therapy (ADT) and took standard doses of the assigned drugs (160 mg of enzalutamide or 50 mg of bicalutamide daily). Both the drugs had similar side effects, although fatigue was more common with enzalutamide.
What is CRPC?
Hormonal therapy is meant to target or block the production of male hormones (androgens) to stop the growth of prostate cancer cells, which need androgen to reproduce. At some point, prostate cancer develops resistance to conventional hormonal therapy. This condition is castration- resistant prostate cancer.
Both studies support the use of enzalutamide rather than bicalutamide in patients with metastatic or nonmetastatic castration-resistant prostate cancer.