Gonadotropin-releasing hormone antagonist in the management of prostate cancer.

Luteinizing hormone-releasing hormone (LHRH) agonist therapy to induce medical castration has become the most common form of hormonal therapy for advanced and metastatic prostate cancer. When treatment is started, LHRH agonists initially stimulate the release of LH, causing a surge in serum testosterone that can precipitate a "flare" phenomenon or worsening of disease, particularly in patients with bone metastatic disease. Gonadotropin-releasing hormone (GnRH) receptor antagonism represents a newer approach to medical castration. Abarelix is a pure GnRH receptor antagonist that is devoid of any LHRH agonist activity. Results from 1 phase II and 3 phase III clinical trials demonstrate that abarelix produces medical castration more quickly and without causing testosterone surge, as compared with LHRH agonists with or without a nonsteroidal antagonist. The safety profile in terms of adverse events is comparable between the 2 types of treatment, but the lack of testosterone surge with abarelix might confer a safety advantage by abolishing the risk of a disease flare.