Endocrine effects of low dose aminoglutethimide as an aromatase inhibitor in the treatment of breast cancer.

The endocrine effects of low dose (62.5 mg, twice a day) aminoglutethimide (AG), without hydrocortisone (HC), escalating at monthly intervals to a conventional dose of AG (500 mg twice a day) combined with HC, were studied in 33 postmenopausal breast cancer patients. Pretreatment serum concentrations of oestrone (E1) and oestradiol (E2) were significantly suppressed by 62.5 mg of AG twice a day. Although further suppression of E1 appeared to occur with 125 mg of AG twice a day, this was not statistically significant. For E1 and E2, higher doses of AG or combined AG and HC failed to cause further significant suppression compared with that obtained at 125 mg of AG twice a day. Significant rises in serum androstenedione were found with all doses of AG alone, although pretreatment concentrations of androstenedione were not significantly altered by combined AG and HC treatment. Mean pretreatment concentrations of dehydroepiandrosterone sulphate (DHA-S) were significantly suppressed by 62.5 mg of AG twice a day and further marked suppression occurred on combined AG and HC therapy. Serum cortisol, aldosterone and plasma ACTH concentrations showed no significant alterations throughout treatment. Aminoglutethimide is as effective at 125 mg twice a day without HC in its suppression of oestrogen levels as at 500 mg twice a day with HC, and its use in this form warrants clinical evaluation.