What are Aromatase Inhibitors and How Do These Drugs Prevent Recurrence?

Question: What are Aromatase Inhibitors and How Do These Drugs Prevent Recurrence?

Aromatase inhibitors are a class of drugs that are given as follow-up treatment to postmenopausal women who have had estrogen-receptor positive breast cancer. These drugs prevent the production of estradiol, a type of estrogen, by inhibiting the enzyme aromatase.

Answer: The hormone estrogen fuels 80% of all breast cancers. Aromatase inhibitors are prescribed after primary treatment (surgery, chemotherapy, radiation) to prevent a recurrence of breast cancer. Before menopause, your ovaries and other tissues (adrenal glands, liver, kidney, and fat tissue) are producing and storing estrogen, keeping your levels of the female hormone high. These drugs are given to postmenopausal women because the ovaries (the primary source of estrogen) stop producing estrogen after menopause.

Aromatase inhibitors differ from SERMs (selective estrogen receptor modulators) in that they lower your levels of circulating estrogen by preventing estrogen production. SERMs do not prevent the production of estrogen, but they help to slow or stop the growth of estrogen-sensitive cancer cells by starving them of a full dose of natural estrogen. Aromatase inhibitors can also be given after a course of SERMs, such as Tamoxifen, to increase your chance of recurrence-free survival. Progestin therapy, such as Megace (megestrol acetate) could be used for metastatic disease.

There are risks and benefits of taking aromatase inhibitors. While they help prevent a recurrence of estrogen-receptor positive breast cancer, they may also:

• increase your risk for osteoporosis (bone thinning)
• raise your cholesterol levels (Femara and Arimidex)
• may cause stomach upset and nausea – these effects usually decrease after a few weeks
• cause menopausal symptoms (hot flashes, vaginal dryness, low libido)

There are four kinds of aromatase inhibitors currently available:

• Arimidex (anastrazole)
• Aromasin (exemestane)
• Femara (letrozole)
• Fadrozole – a third-generation AI

_{Sources:
National Cancer Institute. Dictionary of cancer terms. Aromatase inhibitor.}

National Cancer Institute. Aromatase Inhibitors. Last Updated: 03/19/2007.

American Cancer Society. Hormone Therapy. Last Updated: 09/13/2007.