Aromatase Inhibitors for Breast Cancer
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Aromatase inhibitors are available as tablets. Follow your
doctor's orders or the directions on the label.
How It Works
Aromatase inhibitors interfere with how
estrogen the body's tissues can make. This limits the
amount of estrogen available in the body.
An aromatase inhibitor
cannot lower estrogen levels made by the ovaries. That is why an aromatase
inhibitor only works after
menopause, when a woman's ovaries have stopped making
estrogen and other hormones.1
Why It Is Used
Aromatase inhibitors are used to treat
early estrogen receptor-positive (ER+) breast cancer. They are also used to treat metastatic
or recurrent ER+ breast cancer. An aromatase inhibitor can be used alone or
after tamoxifen treatment.
Some doctors may use aromatase
inhibitors "off-label" to treat infertility and
endometriosis. This means that the U.S. Food and Drug
Administration (FDA) has not approved this use.
How Well It Works
Aromatase inhibitors make it less likely that breast cancer will come back. These medicines work well for postmenopausal women who have had ER+ breast cancer. Studies that compare survival rates for aromatase inhibitors and tamoxifen show that women live about the same length of time when taking either of these medicines.2
may be given to postmenopausal women who have breast cancer, either at the beginning of
treatment or after they are given tamoxifen.
Side effects of an aromatase
inhibitor may include:
- Hot flashes.
- Muscle or body aches.
- Diarrhea or constipation.
- A general feeling of
- Weakness and fatigue.
- Bone thinning. Aromatase inhibitors increase the rate of bone
thinning that occurs normally in postmenopausal women.
See Drug Reference for a full list of side effects. (Drug
Reference is not available in all systems.)
What To Think About
For breast cancer treatment,
aromatase inhibitors should be given only under the supervision of a
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
Smith IE, Chua S (2006). ABC of breast diseases. Medical treatment of early breast cancer. I: Adjuvant treatment. BMJ, 332(7532): 34-37.
National Cancer Institute (2011). Breast Cancer PDQ: Treatment - Health Professional Version. Available online: http://www.cancer.gov/cancertopics/pdq/treatment/breast/HealthProfessional.