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Using Aromatase Inhibitors in Early Stage Breast Cancer

Summary & Participants

Three aromatase inhibitors are being used to fight breast cancer. They are well established as hormonal agents against advanced-stage disease. Now doctors say they offer promise for some women in treating early breast cancer, too.

Medically Reviewed On: June 30, 2008

Webcast Transcript

ANNOUNCER: An estimated 60 to 70 percent of women with breast cancer have a type that grows under stimulation of estrogen. Following treatment by surgery, many of these patients receive hormonal therapy. That has traditionally meant tamoxifen, which blocks estrogen from attaching to cancer cells. Tamoxifen works for women of any age. For women past menopause, great promise is being shown by a new class of drugs -- called aromatase inhibitors. They work by interfering with the production of estrogen.

D. LAWRENCE WICKERHAM, MD: Aromatase is the enzyme that converts actually male hormones into female hormones in postmenopausal women. Premenopausal women get most of their estrogen from the ovary. But postmenopausal women still have estrogen in their body and it's this conversion of androgens coming from other glands in the body to estrogen that needs to be interrupted so that the breast cancer cells no longer have estrogen to stimulate their growth.

GENEROSA GRANA, MD: The aromatase inhibitors that are currently available in the United States are three: Arimidex, or anastrozole; letrozole, also known as Femara; and exemestane, known as Aromasin. All three have been studied in advanced breast cancer. All three are approved for women who have metastatic disease and have failed tamoxifen therapy.

ANNOUNCER: Arimidex and Femara have also been approved for initial treatment in cases where the disease has spread.

D. LAWRENCE WICKERHAM, MD: At the moment, the distinctions between the various aromatase inhibitors are not really apparent. Their benefits and their side effect profiles are remarkably similar and many physicians will choose one over the other simply because they're more comfortable with that particular drug. They have more experience with it.

ANNOUNCER: As aromatase inhibitors proved effective in patients with advanced breast cancer, doctors began to wonder if they could also be used earlier, to fight the disease in patients who were diagnosed before the cancer had spread.

WILLIAM GRADISHAR, MD: When you show that the drugs work well in the metastatic disease setting, you go forward and ask, "Well, if they're good in that setting, they must be or could be risk-reducing in patients with early stage disease."

ANNOUNCER: There were several studies done and in 2004, one of those trials -- known as ATAC - found that although Tamoxifen was effective at preventing early stage recurrence, Arimidex was better. In addition, Arimidex's side effect profile was more tolerable.

ANNOUNCER: There were signs Arimidex may increase a woman's risk of bone fracture. But the drug's side effects generally compared favorably to tamoxifen.

GENEROSA GRANA, MD: We saw less hot flashes. We saw less weight gain, less uterine events -- meaning vaginal bleeding, endometrial cancer, etc. We saw less clotting risk. Clots in the lower extremities, stroke, cardiovascular events.

ANNOUNCER: Studies have been going on for several years to see whether the benefits of hormone therapy can be carried even further with the use of aromatase inhibitors in post-menopausal women. In all of these studies, the aromatase inhibitors showed an improvement in reducing the risk of recurrence. This was true at all of the time points studied: women who took the aromatase inhibitors immediately after surgery, ones who switched from tamoxifen to the aromatase inhibitors after some number of years -- so-called sequencing of hormonal therapy -- and women who added aromatase inhibitors after completing five years of tamoxifen. The aromatase inhibitors have been shown to improve upon the benefits that have already been seen with tamoxifen and should be incorporated into the care of all postmenopausal women with early stage breast cancer.

Although more research is needed, it is clear that aromatase inhibitors are an important new addition to the arsenal of hormonal therapies that have been used to save and prolong womens' lives for over 25 years.