Aromatase inhibitors and breast cancer treatment
Aromatase inhibitors lower estrogen levels in the body by blocking aromatase, an enzyme that converts other hormones into estrogen.
Like tamoxifen, aromatase inhibitors are used to treat metastatic and early breast cancers that are hormone-receptor positive. Examples of aromatase inhibitors include anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara). Unlike tamoxifen, they are only used to treat postmenopausal women.
Aromatase inhibitors come in a pill form and are taken every day.
Postmenopausal women with hormone receptor-positive breast cancer either begin hormone therapy with an aromatase inhibitor or begin with tamoxifen and switch after a few years to an aromatase inhibitor. Treatment with an aromatase inhibitor (alone or after tamoxifen) lowers the risk of [46]:
- Breast cancer recurrence
- Breast cancer in the opposite breast
- Death from breast cancer
Aromatase inhibitors (alone or after tamoxifen) offer the same or better treatment benefit compared to treatment with tamoxifen alone among postmenopausal women with hormone receptor-positive breast cancer [46,53-59]. The aromatase inhibitors anastrozole, exemestane and letrozole all seem to have a similar treatment benefit [46,53-59].
Side effects of aromatase inhibitors
The side effects of aromatase inhibitors differ from those of tamoxifen. Learn more about the side effects of aromatase inhibitors.
Issues still under study
We still do not know how long women should take aromatase inhibitors. At present, there are no data on the benefits or safety of taking aromatase inhibitors for longer than five years.
Another question is whether aromatase inhibitors benefit women who were premenopausal when diagnosed with breast cancer, but later became menopausal because of treatment. New and ongoing studies should help answer such questions.
Aromatase inhibitors are being studied in the chemoprevention setting as well, but it is too early for these results.
To learn more about aromatase inhibitors, visit the National Institutes of Health’s Medline Plus website.
Importance of following your breast cancer treatment plan
The importance of adherence (compliance)
Breast cancer treatment is most effective when all parts of the treatment plan are followed. Adherence (also called compliance) is how closely people follow the treatment plan (for medicines and other therapies) prescribed by their health care providers in terms of:
Completing hormone therapy
Hormone therapy used to treat breast cancer is typically prescribed for at least five years. The length of treatment coupled with side effects can make adherence to hormone therapy difficult. Although the menopausal symptoms related to hormone therapy can be hard to deal with, there are treatments that may ease these side effects. If you have side effects with hormone therapy, talk to your health care provider about ways to treat them.
To get the most benefit of hormone therapy, you need to take the full course of treatment. Women who complete the full treatment course have higher rates of survival [46].
If you have trouble remembering to take your hormone therapy, a daily pillbox or setting an alarm on your watch or phone may be helpful [2]. However, you do not need to panic if you miss a day or two.
Learn more about adherence.
Updated 01/20/12
