Oncologist-approved cancer information from the American Society of Clinical Oncology
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Exemestane Plus Ovarian Function Suppression May be a More Effective Alternative for Premenopausal Women with Early-Stage Breast Cancer

ASCO Annual Meeting
June 1, 2014

In an analysis of two ongoing studies, researchers found that exemestane (Aromasin) was more effective at preventing hormone-sensitive breast cancer from returning for premenopausal women than tamoxifen (Nolvadex, Soltamox) when each drug was paired with ovarian function suppression. Exemestane, an aromatase inhibitor (AI), and tamoxifen are types of hormonal therapy often given as adjuvant therapies to lower the chance of hormone-sensitive breast cancer coming back after other treatments are finished. Hormone-sensitive breast cancer means that the cancer uses the hormones estrogen and/or progesterone to grow.

Although both tamoxifen and AIs such as exemestane are hormonal therapies, they work differently, which affects who can use them. In order for AIs to work effectively, women need to have the low levels of estrogen that naturally occur after menopause, and this is why tamoxifen has been the standard adjuvant hormonal therapy for premenopausal women. In the studies included in this analysis, researchers suppressed ovarian function with medication, surgery to remove the ovaries, or radiation therapy to the ovaries in order to lower women’s estrogen levels to similar levels they would experience after menopause.  

This analysis included information from 4,690 women in two different studies who received either exemestane plus ovarian function suppression or tamoxifen plus ovarian function suppression for five years. Researchers found that the combination of exemestane plus ovarian function suppression reduced the risk of the breast cancer coming back by 34% when compared with tamoxifen plus ovarian function suppression. However, women who received either treatment were equally likely to be alive five years after treatment, with about 96% of women who received exemestane plus ovarian function suppression and about 97% of women who received tamoxifen plus ovarian suppression function alive after five years.

What this means for patients

“For years, tamoxifen has been the standard hormonal therapy for preventing breast cancer recurrences in young women with hormone-sensitive disease. These results confirm that exemestane with ovarian function suppression is a valid alternative,” said lead study author Olivia Pagani, MD, Clinical Director of the Breast Unit at the Oncology Institute of Southern Switzerland in Bellinzona. “Our findings indicate that exemestane is better than tamoxifen, when given with ovarian function suppression, but longer follow-up will be important to assess survival and any long-term side effects and fertility.” These studies are ongoing and, in the United States, tamoxifen is still the recommended adjuvant hormonal therapy for premenopausal women. Though recommendations may change over time, it’s important to talk with your doctor about the best options for you now and why they are recommended. You may also want to discuss the side effects of hormonal therapy, which can differ depending on the type of drug used.

Questions to ask your doctor

  • What type of breast cancer do I have? Is it hormone receptor-positive?
  • Will I need adjuvant hormonal therapy?
  • If so, what type is recommended? Why?
  • What are the side effects, and how can they be managed?

For More Information

Guide to Breast Cancer

Hormonal Therapy for Early-Stage Hormone Receptor-Positive Breast Cancer

Making Decisions About Cancer Treatment

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