Combined Androgen Blockade: The Case for Bicalutamide

Abstract

Combination therapy consists of castration plus an antiandrogen. Following medical or surgical castration, the androgen receptor can be activated by adrenal androgens, low levels of residual testosterone, and ligand-independent activators. The survival benefit of combination therapy compared with castration alone is one of the most studied questions in urology. Results from trials comparing combination therapy to castration alone are variable. A metaanalysis of 26 randomized trials indicated that the type of antiandrogen used is relevant. Combination therapy using nonsteroidal antiandrogens was associated with a statistically significant overall survival benefit. In contrast, combination therapy using steroidal antiandrogens was associated with reduced survival compared with castration alone. Bicalutamide 50 mg has a number of advantages compared with nilutamide and flutamide when used in combination with castration. These include an improved side-effect profile, once-daily dosing, more potent inhibition of androgen-independent activation of the androgen receptor through favorable interactions with nuclear coactivators and corepressors, and evidence for improved survival in one randomized trial. An analysis combining historic trial data suggests that bicalutamide 50 mg in addition to androgen deprivation may reduce the hazard ratio (HR) for prostate cancer mortality by 20% (HR, 0.80; 95% CI, 0.66-0.98).