Effective inhibition by low dose aminoglutethimide of peripheral aromatization in postmenopausal breast cancer patients.

Aminoglutethimide without glucocorticoid has been shown to be a clinically effective treatment for postmenopausal breast cancer in low dosage (250 mg day-1). The mechanism of action of this approach is thought to be the inhibition of peripheral aromatase, the enzyme which converts androstenedione to oestrone. The activity of this enzyme was measured in vivo by injection with 3H-androstenedione and 14C-oestrone and found to be 0.20% +/- 0.05 in 5 patients on low dose AG therapy. In comparison with previously published data this demonstrates a 92% inhibition of peripheral aromatase activity confirming aromatase inhibition as a viable aim in the endocrine treatment of breast cancer.