Aromatase inhibitors are used to treat hormone receptor-positive early and metastatic breast cancers in postmenopausal women.
Learn about aromatase inhibitors and other hormone therapies for metastatic breast cancer.
Hormone receptor-positive breast cancers need estrogen and/or progesterone (female hormones produced in the body) to grow.
Aromatase inhibitors are hormone therapy drugs that can slow or stop the growth of hormone receptor-positive tumors.
They lower estrogen levels in the body by blocking aromatase, an enzyme that converts other hormones into estrogen. This prevents 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 [71,80-83].
Anastrozole, exemestane and letrozole are equally effective and have similar side effects [71,80-83]. 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.
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. It’s usually done with drug therapy so the menopause is temporary.
Women with certain heart problems should not take anastrozole.
Aromatase inhibitors come in pill form. 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.
A recent randomized clinical trial compared outcomes for women who used the aromatase inhibitor letrozole for 10 years versus 5 years .
Women who used letrozole for 10 years had :
However, overall survival was the same whether a woman took the aromatase inhibitor for 5 years or 10 years .
And, women who took letrozole for 10 years continued to have side effects from the drug, including a higher number of bone fractures and a higher rate of osteoporosis .
Talk with your health care provider about the best length of time for you to take an aromatase inhibitor.
Possible side effects of aromatase inhibitors include muscle and 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.
Some premenopausal women may take an aromatase inhibitor though when combined with ovarian suppression, which shuts down the ovaries.
Learn more about ovarian suppression and aromatase inhibitors.
Aromatase inhibitors are also being studied in the chemoprevention (risk-lowering drugs) 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 [84-85].
However, aromatase inhibitors do not have FDA-approval for use in the risk reduction setting.
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 coupled with side effects can make it tough to complete therapy.
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 do not [73-75].
If you have trouble remembering to take your hormone therapy, a pillbox or setting an alarm on your watch or phone (you may be able to download an app) may help .
However, you do not need to panic if you miss a day or two.
Learn more about the importance of following your breast cancer treatment plan.
Anastrozole, exemestane and letrozole all have generic forms. Generics cost less than name brand drugs, but are just as effective.
Medicare and many insurance providers offer prescription drug plans. One may already be included in your policy or you may be able to buy an extra plan for prescriptions.
You may also qualify for programs that help with drug costs or offer low-cost or free prescriptions.
Learn more about insurance plans and prescription drug assistance programs.
Susan G. Komen®’s position on fairness in breast cancer medication coverage
Medications taken by mouth (oral) are usually covered under a health insurance plan’s prescription drug benefit rather than the plan’s medical benefit.
As a result, people often find themselves facing high out-of-pocket costs when filling their prescriptions (sometimes costing thousands of dollars a month).
High prescription drug costs are a barrier to care. They can prevent people from getting the medications prescribed by their health care provider.
Komen supports state and federal efforts to require insurers to provide the same or better coverage for oral breast cancer medications as they do for IV medications. This would help ensure patients have access to affordable, appropriate treatment.
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)
What gives you strength during treatment?