Aromatase Inhibitors

An aromatase inhibitor (AI) is a common type of hormone therapy for cancer. Healthcare providers use these medications to treat estrogen receptor-positive (ER+) breast cancer. ER+ breast cancers grow in response to estrogen. Healthcare providers most commonly prescribe this medicine to women with ER+ breast cancer who have gone through menopause.

Aromatase inhibitors work by reducing the amount of estrogen in your body. Before menopause, your body’s estrogen mostly comes from your ovaries. But afterward, it’s made in other body tissues, such as fat. Aromatase inhibitors block the enzyme that triggers estrogen production outside of your ovaries. In this way, AIs prevent cancer from coming back after breast cancer surgery. They can also slow cancer growth in advanced cancers.

If you have ER+ breast cancer and still get your periods, or if you’re a male with ER+ breast cancer, you’ll likely need a different type of hormone therapy. Or you may take aromatase inhibitors alongside meds called GnRH agonists.

What drugs are aromatase inhibitors?

The three types of aromatase inhibitors are:

• Letrozole
• Anastrozole
• Exemestane

What are the potential benefits and risks?

Aromatase inhibitors are effective cancer fighters. But they can increase the risk of certain diseases and cause side effects of their own. This is because estrogen supports your sexual health, and it regulates other important processes, too. This is why low estrogen from taking an AI may cause issues, such as:

• Increased risk of osteoporosis and bone fractures
• Joint and muscle pain
• Hot flashes
• Vaginal dryness
• Loss of interest in sex
• Trouble sleeping
• Fatigue
• Increased risk of heart disease and diabetes

Experiences of side effects vary. But for most people, the side effects go away once they stop taking the meds. The exceptions are bone loss and changes related to an increased risk of heart disease and diabetes. These can be long-term side effects of taking aromatase inhibitors.

This is why healthcare providers monitor your health during and after treatment. They can prescribe medications that reduce the risks related to these changes.

What happens during treatment?

Aromatase inhibitors are pills you take every day. When you start taking them depends on your situation. Your healthcare provider may prescribe aromatase inhibitor therapy if:

• You’ve had surgery for ER+ breast cancer
• You have ER+ breast cancer that’s spread to nearby lymph nodes
• You have ER+ breast cancer that’s spread to distant organs
• You develop ER+ breast cancer before you’ve gone through menopause (in that case, your ovaries still make estrogen, so you’ll need additional treatment to block these hormones)
• You have ER+ breast cancer and have chosen to switch from a different type of hormone therapy to an AI (this may be an option if your current meds cause unpleasant side effects)

How long will I need this treatment?

Most people take aromatase inhibitors for five to 10 years. Five years is the minimum, but studies show that there are benefits in taking meds for longer, especially if there’s a high risk of cancer returning after surgery. If the cancer is too advanced to be cured, your healthcare provider may advise you to take it for as long as it’s working to slow cancer growth.

Is there anything I can do to make this treatment easier on me?

Aromatase inhibitors can cause major joint pain. In some people, the pain is what causes them to stop treatment. But stopping the meds also stops the cancer-fighting benefits. This is why it’s important to talk to your healthcare provider if you need help managing side effects. They can recommend treatments. They may suggest:

• Adding practices, like yoga and meditation, to your routine
• Receiving acupuncture and cognitive behavioral therapy
• Taking medicines, including duloxetine and NSAIDs, like ibuprofen
• Switching your medication to a different aromatase inhibitor
• Switching to a different type of hormone therapy called tamoxifen

When should I call my healthcare provider?

Call your healthcare provider if:

• Your side effects become more severe than you expected
• Your side effects don’t improve after you switch medications
• You notice changes in your body that may be symptoms of the breast cancer returning (ask your provider about what changes to look out for)

What is the best aromatase inhibitor to take?

While the aromatase inhibitor your healthcare provider prescribes depends on your situation, each is equally effective at treating ER+ breast cancer. Some people may have side effects with one drug type while others don’t. This is why your healthcare provider will work with you to find the best option.