Aromatase inhibitors are a class of medicines that work by blocking the enzyme aromatase, the enzyme that converts androgens into estrogen. Aromatase inhibitors are used in the treatment of breast cancer to reduce levels of circulating estrogen. This means that less estrogen is available to stimulate the growth of estrogen receptor (ER) positive breast cancer cells, slowing or inhibiting the progression of these cancers. Approximately 80% of all breast cancers are ER positive.
Aromatase inhibitors are unable to prevent the ovaries from making estrogen, which means that they are only used to treat breast cancer in postmenopausal women.
There are three aromatase inhibitors: anastrozole, exemestane, and letrozole.