Evaluation of an implant that delivers leuprolide for 1 year for the palliative treatment of prostate cancer

Objectives. To evaluate the Viadur implant, which delivers leuprolide aceta te for the palliative treatment of advanced prostate cancer. Methods. Inserted subcutaneously, the 4 x 45-mm implant uses osmotic pressu re to deliver leuprolide continuously at a controlled rate for 1 year. This 19-center open-label study enrolled patients with prostate cancer who had had no prior therapy or showed biochemical evidence of treatment failure af ter prostatectomy or radiotherapy. Each patient received one implant. After 1 year, that implant was removed, another was inserted, and patients were followed up for 2 additional months. The primary efficacy measure was suppr ession of testosterone to less than the castrate threshold (50 ng/dL). Results. Eighty patients were enrolled. The implant effectively suppressed testosterone in 79 patients (99%) within 2 to 4 weeks and maintained that s uppression through the study period. In 1 patient, the testosterone was sup pressed to less than 100 ng/dL within 4 weeks but was not less than 50 ng/d L until week 24. Prostate-specific antigen levels normalized (4 ng/mL or le ss) or a clinically significant decrease occurred in all patients. Leuproli de was rapidly absorbed, resulting in mean serum concentrations of 16.8 ng/ mL 4 hours after implant insertion and 2.4 ng/mL at 24 hours; steady mean s erum leuprolide concentrations were then maintained throughout the year, at approximately 0.9 ng/ml. Investigators were satisfied with the insertion a nd removal procedures. All patients reported satisfaction after 1 year of t reatment. The safety profile of the implant was consistent with androgen ab lation therapy. Most adverse events were mild, and the most common event wa s hot flashes. Conclusions. The leuprolide implant effectively suppressed testosterone con centrations to less than the castrate threshold and maintained that suppres sion throughout the study period. UROLOGY 55: 639-642, 2000. (C) 2000, Else vier Science Inc.