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Updated ASCO Guidelines Add Arimidex to Recommended Risk-Reducing Medicines for Women at High Risk of Breast Cancer

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Arimidex (chemical name: anastrozole) is now an option to lower breast cancer risk in postmenopausal women at high risk of the disease who have not been diagnosed, according to updated guidelines from the American Society of Clinical Oncology (ASCO).

The updated guidelines were published online on Sept. 3, 2019, by the Journal of Clinical Oncology. Read the abstract of "Use of Endocrine Therapy for Breast Cancer Risk Reduction: ASCO Clinical Practice Guideline 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.

Medicines to reduce risk in women at high risk of breast cancer

If you know you have a high risk of breast cancer because of strong family history or a mutation in a gene linked to breast cancer, such as BRCA1 or BRCA2, there are a number of steps you can take to keep that risk as low as it can be.

Besides lifestyle choices, such as exercising regularly and maintaining a healthy weight, doctors also are likely to recommend women with a high risk of breast cancer take a risk-reducing hormonal therapy medicine. These medicines reduce the risk of hormone-receptor-positive breast cancer, the most common type of breast cancer. The medicines do not reduce the risk of hormone-receptor-negative breast cancer.

The medicines are:

  • tamoxifen (brand names: Nolvadex, Soltamox), a selective estrogen receptor modulator (SERM)
  • Evista (chemical name: raloxifene), also a SERM
  • Aromasin (chemical name: exemestane), an aromatase inhibitor

The updated ASCO guidelines say that doctors now may offer Arimidex, another aromatase inhibitor, as a risk-reducing medicine.

SERMs block the action of estrogen in breast and certain other cells by sitting in the cells’ estrogen receptors. SERMs don’t affect all estrogen receptors the same way because they’re selective (as the name says). In bone cells, SERMs interact with the receptors the way estrogen does and strengthen bones. In breast cells, SERMs block the receptors’ interaction with estrogen and limit cell growth.

Tamoxifen and Evista are pills taken by mouth and can be taken by both premenopausal and postmenopausal women.

Aromatase inhibitors work by stopping the body from producing estrogen, which limits the amount of estrogen available to stimulate hormone-receptor-positive breast cancer cells to grow.

Aromasin and Arimidex are pills taken by mouth and are recommended only for postmenopausal women.

Side effects of risk-reducing medicines

Tamoxifen, Evista, Aromasin, and Arimidex all may cause side effects, some of them severe. Hot flashes and night sweats are side effects of all four medicines, though they’re more common with tamoxifen and Evista. Joint pain is a more common side effect of Aromasin and Arimidex. Aromasin and Arimidex also may weaken bones and make women more likely to break a bone. All four medicines can sometimes cause dangerous blood clots in rare cases. This complication is more common with tamoxifen and Evista.

A number of studies have shown the effectiveness of these medicines for reducing risk in high-risk women who haven't been diagnosed with breast cancer. Still, other research has found that they’re not widely prescribed by doctors or taken by women at high risk because of concerns about side effects.

What this means for you

If you have a higher-than-average risk of breast cancer, it makes sense to do all that you can to keep your risk as low as it can be. You can make lifestyle choices, including:

  • maintaining a healthy weight
  • exercising regularly at the highest intensity possible
  • limiting or avoiding alcohol
  • not smoking
  • eating a diet that is full of fresh, nutrient-dense foods and low in processed foods and foods high in sugar

You and your doctor also may be considering medicine to reduce your risk. Talk to your doctor about your preferences, as well as the risks and benefits of each medicine you’re considering. If you’re already taking hormonal therapy preventively and are having unacceptable side effects, talk to your doctor. There are medicines and complementary medicine techniques, such as acupuncture, that can help ease side effects. You also may be able to switch to a different hormonal therapy medicine. Together, you can make the best choice for your unique situation.

You can learn more about medicines to reduce risk in high-risk women who haven’t been diagnosed on the Hormonal Therapy page.

To talk with others who are at high risk, join the Discussion Board forum High Risk for Breast Cancer.

Written by: Jamie DePolo, senior editor

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

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