Phase III studies to compare goserelin (Zoladex) with orchiectomy and with diethylstilbestrol in treatment of prostatic carcinoma.

Two multicenter, open, randomized phase III clinical trials were conducted in the United Kingdom to compare the effectiveness and safety of the depot formulation of the luteinizing hormone-releasing hormone (LHRH) agonist goserelin (Zoladex, ICI Pharma, Wilmington, Delaware), 3.6 mg sc/28 d, with orchiectomy and with diethylstilbestrol (DES), 1 mg tid, in the treatment of advanced prostatic cancer. In the Zoladex versus orchiectomy trial, there was no significant difference between the treatment groups with regard to subjective and objective responses (British Prostate Group criteria), endocrine responses, clinical effects and side effects, time to treatment failure and death, or survival after similar median follow-up periods. It was concluded that depot Zoladex had behaved as a truly medical alternative to orchiectomy. In the Zoladex versus DES trial, subjective and objective responses (British Prostate Group and National Prostatic Cancer Project criteria), response duration and survival were similar. However, there was a more rapid response to treatment in the depot Zoladex group. Side effects from Zoladex such as flare symptoms during the initial stages of treatment required no discontinuation of therapy; in contrast, 15 percent of patients receiving DES required cessation of therapy during the first three months because of side effects. It was concluded that depot Zoladex was superior to DES in its attainment of an early objective response and in its absence of side effects, and that Zoladex was comparable with DES in terms of response rates and survival.