Endocrine therapy of prostatic carcinoma with slow release (depot) formulation of the LH-RH analog ICI 118630 (Zoladex)]

To investigate the clinical efficacy, safety and endocrinology of ICI 118630 (Zoladex) depot formulation at 3 different dose levels (0.9, 1.8 and 3.6 mg), 90 patients were randomized to receive either one of the 3 doses from April, 1985 to March, 1986 in 28 centers. The depot preparation was injected subcutaneously every 4 weeks 3 times (for up to 12 weeks). Clinical efficacy was evaluated in terms of tumor response and overall subjective response. In 70 patients eligible for tumor response evaluation, 14 out of 22 (63.6%) in the 0.9 mg group, 11 out of 23 (47.8%) in the 1.8 mg group, and 17 out of 25 (68.0%) in the 3.6 mg group showed clinical improvement, that is, either complete response or partial response. In 72 eligible patients for overall subjective response evaluation, clinical subjective improvement was observed in 75.0, 81.8 and 88.0% of the patients in the 3 groups, respectively. There was no significant difference between the groups. As for endocrinology, there were 75 eligible patients. Endocrinological effect was observed in 23 out of 25 (92.0%) in the 0.9 mg group, 100% in both 1.8 mg and 3.6 mg groups. There was no significant difference between the groups. Castration was achieved by week 3.5 +/- 1.7 of therapy on average and by week 2 in the earliest case. There was no significant difference in incidence of side effects between the 3 groups: 5 out of 26 (19.2%) in the 0.9 mg group, 8 out of 29 (27.6%) in the 1.8 mg group, and 2 out of 30 (6.7%) in the 3.6 mg group. Flares presented as an increase in bone pain in 2 and as ureteric obstruction in 2 all in the 1.8 mg group but none in the other 2 dose groups. These flares disappeared on further treatment with Zoladex. These patients showed a clinical-response. The blood level of Zoladex was dose dependent, reaching its peak at week 2 of therapy in all 3 dose groups. There was no evidence of accumulation. Since these results demonstrate that 3.6 mg produces medical castration earlier, it may well be considered as an optimal dose in men.