A phase 3, multicenter, open-label, randomized study of abarelix versus leuprolide acetate in men with prostate cancer

Objectives. To evaluate the levels of testosterone and other hormones in me n with prostate cancer treated with abarelix versus leuprolide acetate. Methods. Patients (n = 269) were randomized to receive open-label abarelix 100 mg or leuprolide acetate 7.5 mg by intramuscular injection. The results of the first 84 days of the study are reported. The primary efficacy endpo ints included avoidance of testosterone surge, castration on day 8, and ach ievement and maintenance of castration from days 29 through 85. The seconda ry endpoints included castration on days 2, 4, and 15; a reduction in prost ate-specific antigen level; and measurements of other hormones. Patients we re monitored for clinical adverse events and laboratory abnormalities. Results. No men in the abarelix group and 82% of men in the leuprolide acet ate group experienced a testosterone surge (P < 0.001). Abarelix caused rap id medical castration: 24% of men 1 day after treatment and 78% after 7 day s compared with 0% of men treated with leuprolide acetate on either day. A comparable percentage of men achieved and maintained castration between day s 29 and 85 in each group. Prostate-specific antigen had a statistically si gnificant decrease for the first month in patients treated with abarelix. D ihydrotestosterone, luteinizing hormone, prostate-specific antigen, and fol licle-stimulating hormone showed similar rapid reductions without an initia l increase. The overall occurrence of adverse events was similar across the treatment groups, and most were sequelae of comorbid disorders. Conclusions. Treatment with abarelix produced a higher percentage of patien ts who avoided a testosterone surge and had a more rapid time to testostero ne suppression with a higher rate of medical castration I day after treatme nt and greater reductions in testosterone, luteinizing hormone, follicle-st imulating hormone, and dihydrotestosterone during the first 2 weeks of trea tment compared with leuprolide acetate. The achievement and maintenance of castration was comparable between the two groups. (C) 2001, Elsevier Scienc e Inc.