Aromatase inhibitors
Aromatase inhibitors — anastrozole, letrozole, and exemestane — lower the amount of estrogen in the body by blocking aromatase, the enzyme the body uses to make estrogen in the ovaries and other tissues. They are used mainly in postmenopausal women with hormone receptor–positive breast cancer; before menopause they can be given only together with a drug that suppresses ovarian function. Their side effects resemble those of tamoxifen, including hot flashes and night sweats.
How it works
After menopause the ovaries stop making estrogen, but small amounts are still produced in other tissues, where the enzyme aromatase converts androgens into estrogen. Anastrozole, letrozole, and exemestane block this enzyme, so estrogen levels fall and hormone-dependent breast cancer cells lose the signal that drives their growth.
In premenopausal women the ovaries produce too much aromatase for these drugs to block effectively on their own. For this reason, before menopause aromatase inhibitors are combined with ovarian suppression — for example with a GnRH agonist — which switches off hormone production in the ovaries.
Used in
Invasive Breast Carcinoma
C50
standard hormone therapy in postmenopausal hormone receptor-positive disease