Aromatase Inhibitors
Aromatase inhibitors are a hormone therapy (also called endocrine therapy). They are used to treat hormone receptor-positive early, locally advanced and metastatic breast cancers.
Learn about aromatase inhibitors and other hormone therapies for metastatic breast cancer.
How do aromatase inhibitors work?
Hormone receptor-positive breast cancers need estrogen and/or progesterone (female hormones) to grow.
Aromatase inhibitors lower estrogen levels in the body by blocking aromatase, an enzyme that converts other hormones into estrogen. This slows or stops the growth of the tumor by preventing the cancer cells from getting the hormones they need to grow.
Aromatase inhibitors include:
- Anastrozole (Arimidex)
- Exemestane (Aromasin)
- Letrozole (Femara)
To learn about a specific aromatase inhibitor, visit the National Institutes of Health’s Medline Plus website.
Aromatase inhibitors and treatment for early and locally advanced breast cancers
For women with hormone receptor-positive breast cancer, treatment with an aromatase inhibitor (alone or after several years of tamoxifen) lowers the risk of [91]:
- Breast cancer recurrence
- Breast cancer in the opposite breast
- Death from breast cancer
Among postmenopausal women with hormone receptor-positive breast cancer, aromatase inhibitors (alone or after tamoxifen) offer the same or slightly greater benefit compared to tamoxifen alone [91,105-108].
Anastrozole, exemestane and letrozole are equally effective and have similar side effects [91,105-108]. However, you may tolerate one drug better than another.
Learn about aromatase inhibitors and treatment for metastatic breast cancer.
| For a summary of research studies on aromatase inhibitors and early breast cancer, visit the Breast Cancer Research Studies section. |
Who can take aromatase inhibitors?
Aromatase inhibitors are used to treat breast cancer in women. In rare cases, they are used to treat breast cancer in men.
Menopausal status
In general, aromatase inhibitors are only used to treat breast cancer in postmenopausal women.
However, some premenopausal women may take an aromatase inhibitor when combined with ovarian suppression.
Ovarian suppression prevents the ovaries from making estrogen, so a woman becomes postmenopausal. Ovarian suppression is usually done with drug therapy, so menopause may be temporary.
How are aromatase inhibitors taken?
Aromatase inhibitors are pills. You take one pill every day.
Postmenopausal women with hormone receptor-positive breast cancer can:
- Begin hormone therapy with an aromatase inhibitor
- Begin hormone therapy with tamoxifen and then after a few years, switch to an aromatase inhibitor
When an aromatase inhibitor is the only hormone therapy given, it’s taken for 5-10 years.
When an aromatase inhibitor is taken after tamoxifen, the drugs are taken for a combined total of 5-10 years.
Talk with your health care provider about how long you should take an aromatase inhibitor.
Find a list of questions on hormone therapy you may want to ask your health care provider.
Length of treatment with an aromatase inhibitor
Randomized clinical trials have compared outcomes for women who used aromatase inhibitors for 10 years versus 5 years [109]. Taking an aromatase inhibitor for 10 years [109]:
- Improves disease-free survival
- Lowers the risk of cancer in the opposite breast (contralateral breast cancer)
However, overall survival is the same whether a woman takes an aromatase inhibitor for 5 years or 10 years [109]. For most women, the benefit of the extra 5 years of treatment is small [109].
Women who take an aromatase inhibitor for more than 5 years continue to have side effects from the drug, including a higher number of bone fractures and a higher rate of osteoporosis [109-112].
Talk with your health care provider about how long you should take an aromatase inhibitor.
Learn about the importance of completing treatment with an aromatase inhibitor.
Importance of following your breast cancer treatment plan
Breast cancer treatment is most effective when all parts of the treatment plan are followed as prescribed.
Prescription drug assistance
Hormone therapy drug costs can quickly become a financial burden for you and your family.
Medicare and many insurance companies offer prescription drug plans. One may already be included in your policy, or you may be able to buy an extra plan for prescriptions.
Aromatase inhibitors are pills, so they’re covered under your health insurance plan’s prescription drug benefit rather than the plan’s medical benefit. This means there are usually out-of-pocket costs, which can add up over time.
You may qualify for programs that help with drug costs or offer low-cost or free prescriptions.
Aromatase inhibitors are all available in a generic form. Generics cost less than name brand drugs but are just as effective.
Learn more about insurance plans and prescription drug assistance programs.
Learn about other financial assistance programs.
Komen Financial Assistance Program |
Susan G. Komen® created the Komen Financial Assistance Program to help those struggling with the costs of breast cancer treatment by providing financial assistance to eligible individuals. Funding is available for eligible individuals undergoing breast cancer treatment at any stage or living with metastatic breast cancer (stage IV). To learn more about this program and other helpful resources, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636) or email helpline@komen.org. Se habla español. |
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Susan G. Komen®‘s position on fairness in oral cancer drug coverage |
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Insurance coverage of oral cancer drugs Cancer medications given by vein (through an IV) or injection (under the skin or into a muscle) are usually covered under a health insurance plan’s medical benefit. However, cancer medications that are pills (oral cancer drugs) are usually covered under a health insurance plan’s prescription drug benefit. As a result, people often find themselves facing high out-of-pocket costs when filling prescriptions for oral cancer drugs. Sometimes these costs can be thousands of dollars a month. The impact of high cost-sharing High prescription drug costs and the resulting out-of-pocket burden on patients are a barrier to care. They can prevent people from getting the medications prescribed by their health care providers. No one should be forced to get less appropriate treatment because an insurer gives more coverage for IV and injectable drugs than pills. Efforts to increase fairness in drug coverage Komen supports state and federal efforts to require insurers to provide the same or better coverage for oral cancer drugs as they do for IV and injectable cancer drugs. This would help make sure patients have access to affordable, appropriate treatment. Become a Komen Advocacy Insider Sign up to be a Komen Advocacy Insider and get informed when action is needed on drug coverage issues at the state or national level. |
SUSAN G. KOMEN® SUPPORT RESOURCES |
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Updated 06/27/22
