Aromatase inhibition: 4-hydroxyandrostenedione (4-OHA, CGP 32349) in advanced prostatic cancer.

We report the use of the steroidal aromatase inhibitor, 4-hydroxyandrostenedione (4-OHA, CGP 32349), in the management of patients with advanced, hormone resistant, prostatic cancer. Eighteen of 25 patients (72%) showed a subjective response, mainly in the form of pain relief and increased performance. There were no objective improvements. A tumour flare occurred in 17/25 (68%). Detailed endocrine studies were performed during treatment. These showed that suppression of serum oestradiol levels occurred in 19/25 (76%) of patients during treatment with 4-OHA. Serum levels of androstenedione increased in 9/14 patients (64%). Concentration of serum testosterone and 5 alpha-dihydrotestosterone were elevated in 3/14 (21%) and 2/11 (18%) patients respectively. There appeared to be no correlation between response or tumour flare and changes in steroid levels during treatment with 4-OHA. The mechanism of action of 4-OHA in palliating patients with advanced prostatic cancer remains obscure. 4-OHA or its metabolites may be acting on metastatic bone metabolism via effects on oestrogen related osteoclastic and osteoblastic activity. Further investigation of the effects of aromatase inhibitors on prostatic biology, and bone metabolism in patients with metastatic prostate cancer, would appear worthwhile.