Aromatase inhibitors

Aromatase inhibitors used in breast cancer are drugs that inhibit the trans formation of androstenedione and testosterone, respectively in estradiol a nd estrone. Two classes have been described: steroidal inhibitors which act competitively and irreversibly and non steroidal inhibitors which block th e P 450 cytochrome. The first one is aminoglutethimide which has an adrenal effect on 11, 18 and 21 hydroxylase. Rogletimide, less powerful and less s pecific is a aminoglutethimide analogue The response rates obtained with fo rmestane is not different. The clinical development has been stopped due to a lack of specificity. Letrozole, vorozole, exemestane and anastrozole are more powerful and more specific. Letrozole and vorozole are at least as ef ficient and better tolerated than aminoglutethimide. Anastrozole, letrozole and vorozole are at least as efficient as megestrol acetate and better tol erated in advanced breast cancer patients receiving a second line hormone t herapy.