Estrogen receptor status and the clinical response to a combination of aminoglutethimide and cortisol in advanced breast cancer

Mechanisms of action of aminoglutethimide as endocrine therapy of breast cancer

During the last decade aminoglutethimide has been recognised as a valuable alternative in endocrine therapy for advanced breast cancer. Although some side effects do occur, most often these are initial effects which subside within a few weeks, and cessation of therapy is not usually indicated. Aminoglutethimide was originally introduced as an inhibitor of steroidogenesis in the adrenal cortex. It was soon recognised, however, that inhibition of the non-glandular aromatase, blocking the conversion of androgenic prohormones to oestrogens, was more important, resulting in decreased blood levels of oestrogens. In this review the role of aromatase inhibition as the only important aspect of the mechanism of action of aminoglutethimide is challenged. Evidence has accumulated during the last few years that aminoglutethimide is a most potent inducer of microsomal enzymes. In addition to the pharmacological implications this has (suggesting important interactions), it also points to the possibility that levels of oestrogens are decreased due to accelerated metabolism of these hormones. Based on new experimental data, and also clinical work with alternative aromatase inhibitors, it appears that the antitumour activity of aminoglutethimide may be due to both aromatase inhibition and accelerated metabolism of oestrogens. This seriously challenges the importance of aromatase inhibition alone as a strategy in endocrine therapy of breast cancer, and furthermore suggests that accelerated metabolism of key hormones is an alternative strategy to be explored.

Could aminoglutethimide replace adrenalectomy?

Could aminoglutethimide replace adrenalectomy? This question has already been answered in clinical practice in the United Kingdom, for surgical adrenalectomy has declined markedly in frequency as new hormonal therapy has appeared. An optimal assessment of an endocrine therapy can only be made in previously untreated patients because of the heterogeneity of previously treated populations. Thus aminoglutethimide (AG) and adrenalectomy have been compared for previously untreated and treated populations. Because AG is commonly called 'medical adrenalectomy', this article will review and compare aminoglutethimide therapy with surgical adrenalectomy and make the case that surgical adrenalectomy is no longer indicated in the management of breast cancer.