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.
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:
To learn about a specific aromatase inhibitor, visit the National Institutes of Health's Medline Plus website.
For women with hormone receptor-positive breast cancer, treatment with an aromatase inhibitor (alone or after several years of tamoxifen) lowers the risk of :
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 [79,90-93].
Anastrozole, exemestane and letrozole are equally effective and have similar side effects [79,90-93]. However, you may tolerate one drug better than another.
For a summary of research studies on aromatase inhibitors and early breast cancer, visit the Breast Cancer Research Studies section.
Aromatase inhibitors are used to treat breast cancer in women. They are not used to treat breast cancer in men.
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 is temporary.
Aromatase inhibitors are pills. You take one pill every day.
Postmenopausal women with hormone receptor-positive breast cancer can:
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 for your health care provider.
Randomized clinical trials have compared outcomes for women who used aromatase inhibitors for 10 years versus 5 years . Taking an aromatase inhibitor for 10 years :
However, overall survival is the same whether a woman takes an aromatase inhibitor for 5 years or 10 years . For most women, the benefit of the extra 5 years of treatment is small .
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 [94-96].
Learn about the importance of completing treatment with an aromatase inhibitor.
Possible side effects of aromatase inhibitors include muscle pain, joint pain and menopausal symptoms (such as hot flashes).
Aromatase inhibitors also cause a loss of bone density. Women who take an aromatase inhibitor get a baseline measure of their bone density so changes to bone density can be monitored.
Learn more about the side effects of aromatase inhibitors.
Aromatase inhibitors don’t normally work in premenopausal women because their ovaries are still making estrogen.
However, some premenopausal women may take an aromatase inhibitor when combined with ovarian suppression, which shuts down the ovaries.
Learn more about ovarian suppression and aromatase inhibitors.
Aromatase inhibitors have been studied in the risk reduction setting.
Findings from randomized controlled trials have shown the aromatase inhibitors exemestane and anastrozole may lower the risk of developing breast cancer in postmenopausal women at high risk [97-98].
However, aromatase inhibitors are not FDA-approved for use as risk-lowering drugs.
Learn more about risk-lowering drugs for women at high risk of breast cancer.
Breast cancer treatment is most effective when all parts of the treatment plan are followed as prescribed.
It’s important to follow the treatment plan (for medications and other therapies) prescribed by your health care provider in terms of:
Aromatase inhibitors are prescribed for 5-10 years. The length of this treatment along with side effects can make it tough to complete treatment.
Dealing with menopausal symptoms related to hormone therapy can be hard. Talk with your health care provider about ways to ease these and other side effects.
To get the most benefit out of hormone therapy, you need the full course of treatment. Women who complete the full course have better survival than those who don't [82-84].
If you have trouble remembering to take your medicine, a pillbox or setting an alarm on your watch or phone (you may be able to download an app) may help .
However, you don't need to panic if you miss a day or two.
Learn more about the importance of following your breast cancer treatment plan.
Learn about ways to manage hot flashes and other menopausal symptoms.
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.
Anastrozole, exemestane and letrozole all have generic forms. 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.
Susan G. Komen®’s position on fairness in oral cancer drug coverage
Insurance coverage of oral cancer drugs
Cancer medications given by vein (through an IV) 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.
As a result, people often find themselves facing high out-of-pocket costs when filling prescriptions for oral cancer drugs. Sometimes this can cost thousands of dollars a month.
The impact of high drug costs
High prescription drug costs 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 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 cancer drugs. This would help ensure patients have access to affordable, appropriate treatment.
Ask your U.S. representative to co-sponsor the Cancer Drug Parity Act.
Komen Treatment Assistance Program
Susan G. Komen® offers the Komen Treatment Assistance Program to help eligible, underserved breast cancer patients in treatment. 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).
SUSAN G. KOMEN® SUPPORT RESOURCES
Hormone Therapy Video
Facts for Life: Hormone Therapy
Breast Cancer 101 - Aromatase Inhibitors
1-877 GO KOMEN(1-877-465-6636)
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