Aromatase inhibitors

Aromatase inhibitors are commonly used to treat breast cancer that's hormone receptor positive. These drugs are also an option for breast cancer chemoprevention.

How they work

Aromatase inhibitors are a class of medicines that reduce the amount of estrogen in your body, depriving breast cancer cells of the fuel they need to grow and thrive.

Three aromatase inhibitors are currently approved in the United States for breast cancer treatment: anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara).

These medications are used to treat breast cancer that's estrogen- or progesterone-responsive in those who've undergone menopause.

Who they're for

Aromatase inhibitors have been studied and shown to be effective to treat breast cancer and to prevent breast cancer recurrence after menopause. Aromatase inhibitors are not intended for preventing breast cancer recurrence if you still have menstrual cycles.

Aromatase inhibitors, specifically exemestane and anastrozole, have also been studied to see if they may reduce the risk of breast cancer in people at high risk, such as those with a family history of breast cancer or a history of precancerous breast lesions. Studies have shown promise in reducing breast cancer risk in these individuals.

Based on these results, you and your health care provider may choose to use aromatase inhibitors to reduce the risk of breast cancer, though these drugs aren't approved by the U.S. Food and Drug Administration for this use.

Additional studies are underway to determine whether aromatase inhibitors may reduce the risk of breast cancer in those with genetic mutations that increase the risk of breast cancer.

Common side effects

Common side effects of aromatase inhibitors include:

• Hot flashes
• Vaginal dryness
• Joint and muscle pain
• Headache
• Fatigue

Risks

Aromatase inhibitors increase the risk of osteoporosis.

Aromatase inhibitors aren't associated with an increased risk of blood clots or uterine cancer, as tamoxifen and raloxifene are. Because aromatase inhibitors are a newer class of medications, more research needs to be done about long-term health risks, such as heart disease and broken bones.

As more results from research studies become available, health care providers will have a better idea of the long-term health implications for these drugs and their effectiveness in breast cancer chemoprevention.