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Updated ASCO Guidelines Recommend Extended Hormonal Therapy With Aromatase Inhibitors for Postmenopausal Women With Hormone-Receptor-Positive Breast Cancer

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After surgery, people diagnosed with early-stage, 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.

The American Society of Clinical Oncology (ASCO) has updated its guidelines on adjuvant hormonal therapy, recommending postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer that has spread to the lymph nodes (node-positive disease) be treated with hormonal therapy, including an aromatase inhibitor, for 10 years after surgery. Doctors call taking hormonal therapy for 10 years after surgery extended adjuvant hormonal therapy.

The guidelines also say that many postmenopausal women diagnosed with early-stage, node-negative, hormone-receptor-positive breast cancer should consider extended hormonal therapy, including an aromatase inhibitor, based on their risk of recurrence.

The updated guidelines were published online on Nov. 19, 2018, by the Journal of Clinical Oncology. Read “Adjuvant Endocrine Therapy for Women With Hormone Receptor-Positive Breast Cancer: ASCO Clinical Practice Guideline Focused Update.” (PDF)

How do hormonal therapy medicines work?

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 commonly used to reduce recurrence risk in premenopausal women.

For many years, women took hormonal therapy for 5 years after breast cancer surgery. Then research found that taking tamoxifen for 10 years instead of 5 years after surgery lowered a woman’s risk of recurrence, as well as improved survival. Taking tamoxifen for 10 years after surgery became the standard of care in 2014. But more research was needed to see if taking an aromatase inhibitor for 10 years instead of 5 would offer more benefits.

That research has now been done, which is why ASCO updated its guidelines.

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 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., professor of medicine at the University of Michigan
  • Clifford Hudis, M.D., F.A.C.P., F.A.S.C.O., chief executive officer of ASCO
  • Eric Winer, M.D., professor of medicine at Harvard Medical School and chief of the Susan F. Smith Center for Women’s Cancers, who also holds the Thompson Chair in Breast Cancer Research

Updated guideline recommendations

The updated guidelines are based on the results of six large trials looking at whether taking an aromatase inhibitor for more than 5 years offered additional benefits. The studies found that extended aromatase inhibitor treatment didn’t seem to improve overall survival, but it did significantly reduce the risk of breast cancer recurrence and the risk of breast cancer developing in the opposite breast.

For postmenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer, the updated guidelines say:

  • Many women diagnosed with node-negative disease may be good candidates for 10 years of treatment with an aromatase inhibitor after breast cancer surgery. Still, since the recurrence risk for node-negative disease is generally lower than the recurrence risk for node-positive disease, the benefits will likely be smaller for this group of women. Women with node-negative disease with a low risk of recurrence should not routinely be offered extended hormonal therapy.
  • Women diagnosed with node-positive disease should be offered extended aromatase inhibitor treatment after breast cancer surgery, for up to a total of 10 years of aromatase inhibitor treatment.
  • Women who receive extended hormonal therapy treatment after surgery should received no more than 10 years of hormonal therapy treatment.
  • A woman’s risk of a new, second breast cancer and her risk of breast cancer in the opposite breast should be factors in deciding whether a woman receives extended hormonal therapy treatment.
  • Ten years of hormonal therapy comes with risks and side effects, as well as benefits. Women and their doctors should weigh these risks against the benefits when making decisions about extended hormonal therapy treatment.

Weighing the risks and benefits of extended hormonal therapy treatment

As the guidelines say, 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 for many women.

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 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 pages on Staying on Track With Treatment.

To talk with others about your experiences with hormonal therapy, visit the Discussion Board forum Hormonal Therapy - Before, During, and After.

Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser

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