Phase II study of Zoladex depot in advanced prostatic cancer with special reference to criteria of response and survival.

Abstract

Zoladex is a potent decapeptide analogue of luteinising hormone releasing hormone (LHRH). The drug is formulated as a 3.6 mg depot dispersed in a matrix of d,l-lactide-glycolide copolymer, which is totally biodegradable. This formula releases drug continuously for at least 28 days and reliably suppresses serum testosterone into the castrate range. The effect of the depot was studied in 29 patients with locally advanced or metastatic carcinoma of the prostate. Average age at entry was 71 years (range 52-87) and follow-up was from 13.5 to 34.5 months (median 23). Endocrine studies showed that medical castration was maintained in all cases. Three patients experienced bone pain in the first month of treatment and two others had temporary nephrostomies for worsening ureteric obstruction. Subjective improvement was seen in 23/28 cases (82%). There were no complete responses, but partial response was seen in 24/28 (85.7%) using our own criteria, 24/28 (85.7%) using the criteria recommended by the British Prostate Group (BPG) and 15/28 (53.6%) using NPCP criteria. Stable disease was seen in 3/28 patients (10.7%) by our own or BPG criteria, and in 12/28 patients (42.9%) according to NPCP criteria. Progression of disease was measurable in 21 patients (72.4%) whatever criteria were applied; 11/29 (37.9%) have died, giving a median survival of 10 months (range 2.4-26). Following these encouraging results, a multicentre randomised comparative study with stilboestrol 3 mg daily is being undertaken.