After surgery, women diagnosed with hormone-receptor-positive breast cancer usually take hormonal therapy medicine to reduce the risk of the cancer coming back (recurrence). Hormonal therapy given after surgery is called adjuvant hormonal therapy.
Hormonal therapy medicines work in two ways:
- by lowering the amount of estrogen in the body
- by blocking the action of estrogen on breast cancer cells
There are several types of hormonal therapy medicines. Tamoxifen, a selective estrogen receptor modulator (SERM), is one of the most well-known. Tamoxifen can be used to treat both premenopausal and postmenopausal women. In the early 2000s, the aromatase inhibitors:
- Arimidex (chemical name: anastrozole)
- Aromasin (chemical name: exemestane)
- Femara (chemical name: letrozole)
were shown to be more effective at reducing recurrence risk in postmenopausal women and are now used more often than tamoxifen to treat women who’ve gone through menopause. Aromatase inhibitors aren’t used to reduce recurrence risk in premenopausal women.
The American Society of Clinical Oncology (ASCO) has developed new guidelines on adjuvant hormonal therapy that recommend all women diagnosed with hormone-receptor-positive breast cancer be offered the option of taking hormonal therapy for 10 years.
The guidelines were published online on May 27, 2014 by the Journal of Clinical Oncology. Read the abstract of “Adjuvant Endocrine Therapy for Women With Hormone Receptor-Positive Breast Cancer: American Society of Clinical Oncology Clinical Practice Guideline Focused Update.”
ASCO is a national organization of oncologists and other cancer care providers. ASCO guidelines give doctors recommendations for treatments and testing that are supported by much credible research and experience.
Four of the experts who wrote the new guidelines are members of the Breastcancer.org Professional Advisory Board:
- Thomas Buchholz, M.D., F.A.C.R., professor and chairperson of the Department of Radiation Oncology at the University of Texas M.D. Anderson Cancer Center; he also holds the Frank T. McGraw Chair for the Study of Cancer
- Jennifer Griggs, M.D., M.P.H., associate professor of medicine at the University of Michigan
- Clifford Hudis, M.D., chief of the Breast Cancer Medicine Service and attending physician at Memorial Sloan-Kettering Cancer Center and professor of medicine at the Weill Medical College of Cornell University; Dr. Hudis currently serves as president of ASCO
- Eric Winer, M.D., associate professor of medicine at Harvard Medical School and director of the Dana-Farber Cancer Institute’s Gillette Center for Women’s Cancers Breast Oncology Center
The new guidelines are based on the results of large studies showing that taking tamoxifen for 10 years instead of 5 years after surgery:
- lowers the risk of recurrence
- improves breast cancer survival rates
- improves overall survival rates
For women diagnosed with hormone-receptor-positive breast cancer, the updated ASCO guidelines recommend:
- newly diagnosed premenopausal and perimenopausal women take 5 years of tamoxifen as their first hormonal therapy; after this first 5 years is done, the hormonal therapy taken for the second 5 years (for a total of 10 years of hormonal therapy) would be determined by the woman’s menopausal status:
- postmenopausal women could take another 5 years of tamoxifen or switch to an aromatase inhibitor for 5 years
- pre- and perimenopausal women would take another 5 years of tamoxifen
- newly diagnosed postmenopausal women have several options:
- take tamoxifen for 10 years
- take an aromatase inhibitor for 5 years; right now, there isn’t enough evidence to recommend taking an aromatase inhibitor for 10 years
- take tamoxifen for 5 years and then switch to an aromatase inhibitor for another 5 years (for a total of 10 years of hormonal therapy)
- take tamoxifen for 2 to 3 years and then switch to an aromatase inhibitor for another 5 years (for a total of 7 to 8 years of hormonal therapy)
- postmenopausal women who started taking an aromatase inhibitor but didn’t finish 5 years of treatment can switch to tamoxifen to complete 5 years of hormonal therapy
- postmenopausal women who started taking tamoxifen but didn’t finish 5 years of treatment can switch to an aromatase inhibitor and take it for 5 years (for a total of 7 to 8 years of hormonal therapy
Both tamoxifen and aromatase inhibitors can cause side effects. Tamoxifen may cause hot flashes and increase the risk of blood clots and stroke. Aromatase inhibitors may cause muscle and joint aches and pains, as well as hot flashes. Less common but more severe side effects of aromatase inhibitors are heart problems, osteoporosis, and broken bones. Still, the benefits of taking hormonal therapy for 10 years outweigh the risks.
If you’ve been diagnosed with early-stage, hormone-receptor-positive breast cancer, it’s likely that you will take some type of hormonal therapy medicine for up to 10 years. If your doctor doesn’t recommend extended hormonal therapy treatment for you, it’s a good idea to ask why. Together, you can decide on a treatment plan that’s best for you.
Visit the Breastcancer.org Hormonal Therapy pages for more information.
It’s also important to talk to your doctor if you’re having troublesome side effects from your hormonal therapy medicine. There are ways to manage these side effects, including acupuncture and exercise. You also may be able to switch to a different hormonal therapy.
For more information, visit the Breastcancer.org pages on Staying on Track With Treatment.
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