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Aromatase Inhibitors or Tamoxifen

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Last Modified: February 20, 2009

Dear OncoLink "Ask The Experts,"

I am post-menopausal and have been prescribed an aromatase inhibitor. Why am I receiving this when it seems like tamoxifen is the more common prescription? How can I deal with the hot flashes caused by this drug?

Carolyn Vachani RN, MSN, AOCN, OncoLink's Nurse Educator, responds:

Tamoxifen is the drug of choice for premenopausal women with hormone receptor-positive breast cancer. This is based on how it works. The main source of estrogen in premenopausal women is the ovaries. Tamoxifen is an antiestrogen or estrogen blocker, which works by blocking estrogen receptors in breast tissue. While estrogen may not actually cause breast cancer, it is necessary in order for the cancer to grow in some breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.

The aromatase inhibitors go a step further, by preventing the estrogen from being produced. In women who have gone through menopause, estrogen is mainly produced by converting androgens (sex hormones produced by the adrenal glands) into estrogens. An enzyme called aromatase is responsible for this conversion. Aromatase inhibitors block this conversion, leading to less estrogen in the body. These drugs have been found to be more effective at preventing cancer recurrence in post menopausal women.

As for dealing with the side effects of hot flashes, see this previous question.