Treatment of advanced prostatic cancer with LHRH analogue ICI 118630: clinical response and hormonal mechanisms

9 of 12 patients with advanced metastatic carcinoma of the prostate treated with luteinising-hormone-releasing-hormone (LHRH) analogue ICI 118630 for a mean period of 6 months showed objective evidence of response to treatment. Of 8 patients with bone pain, 7 obtained relief. After 6 weeks of treatment testosterone concentrations were reduced to castrate levels (range less than 2 to 5.5 nmol/l) from a pretreatment mean value of 15.7 nmol/l (range 10.3-24 nmol/l). Basal gonadotropin levels and gonadotropin responses to acute LHRH stimulation were suppressed within 2 weeks of treatment. However, the testosterone response to stimulation with human chorionic gonadotropin was unimpaired 4 weeks after the start of treatment. Therefore suppression of the basal testosterone concentration by ICI 118630 was due to inhibition of pituitary luteinising-hormone secretion rather than direct inhibition of testicular Leydig-cell function. ICI 118630 offers an alternative treatment to orchidectomy and oestrogen therapy.