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Using Aromatase Inhibitors in Early Stage Breast Cancer

Breast Cancer Breast Cancer Treatment Hormone Therapy

Understanding Hormonal Therapy for Early Stage Breast Cancer

Summary & Participants

Studies show great promise for drugs called aromatase inhibitors in fighting the recurrence of breast cancer. Find out who may benefit, and what advantages these drugs may hold over tamoxifen.

Medically Reviewed On: June 30, 2008

Webcast Transcript

ANNOUNCER: Even when a woman with breast cancer is diagnosed early, she faces a significant risk of having the disease recur, after initial treatment by surgery.

GENEROSA GRANA, MD: To give you an example, a woman who has a 2 centimeter tumor and clean lymph nodes still has a 20% risk of developing metastatic spread of her cancer. That means that over the next 5 years, if no treatment is undertaken, she has approximately a 20% chance of developing spread of this cancer to the lungs, liver or bone.

ANNOUNCER: So while surgery is usually the first line of attack against breast cancer, most patients also undergo what's called "adjuvant therapy" to battle recurrence.

One approach is hormonal therapy, for a type of cancer that grows under stimulation of estrogen. Whether a woman has this type of cancer is usually determined by lab tests following initial treatment.

GENEROSA GRANA, MD: The presence of estrogen and progesterone receptors in cancer cells are determined at the time of surgery. When a woman has a biopsy, the tumor is tested for the presence of estrogen and progesterone receptors.

WILLIAM GRANDISHAR, MD: Estrogen and progesterone receptors are proteins that are present on the majority of breast cancers that develop in humans. Not all patients actually have tumors that have these estrogen and progesterone receptors. But when present, they indicate to us that manipulating the tumor using hormone therapy may be a possibility.

ANNOUNCER: For over 20 years, hormonal therapy has usually meant tamoxifen, the most widely used drug against breast cancer. Tamoxifen binds to estrogen receptors on cancer cells, preventing estrogen from doing so.

Tamoxifen is effective in women regardless of their age. But for women who are past menopause, there's another approach to hormonal therapy-using drugs that block the production of estrogen.

More recently, there is information that a class of drugs called the aromatase inhibitors can also reduce the risk of the disease coming back. Aromatase inhibitors work only after menopause, when there are much smaller quantities of estrogen in a woman's body when her ovaries have stopped producing the hormone.

WILLIAM GRANDISHAR, MD: What the aromatase inhibitors do in a postmenopausal woman is they drive down or eliminate the last little bit of estrogen that's made by the body, even though the ovaries aren't functioning any more. And they do that by inhibiting a particular enzyme that's present in other parts of the body, such as fatty tissue, the liver, hair follicles and by interfering with that enzyme, they eliminate or almost completely eliminate any estrogen left in the body.

ANNOUNCER: There are three drugs in this class: Arimidex, Femara, and Aromasin. Arimidex has been approved for adjuvant use against all types of breast cancers including early-stage disease, when the cancer has not spread beyond the breast. Femara is approved for locally advanced cancer and metastatic cancer. And Aromasin has been approved for use against metastatic cancer if tamoxifen has proved ineffective.

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 women's lives for over 25 years.