A new class of drugs could reduce the risk of breast cancer recurrence in post-menopausal women. Exemestane is a third-generation aromatase inhibitor. Aromatase inhibitors are drugs that block the conversion of precursor molecules. In the case of breast cancer, aromatase inhibitors block the conversion of precursor molecules into various types of estrogenic compounds. In a new study, coordinated through the National Surgical Adjuvant Breast and Bowel Project, researchers are studying exemestane to determine if it can further reduce the risk of breast cancer recurrence among post-menopausal women.
John Cole, M.D., from the Ochsner Clinic in New Orleans, explains the ovaries in post-menopausal women no longer make estrogen. However, estrogen is still produced from the adrenal glands and from fatty tissues. He says by using an aromatase inhibitor like exemestane, that small residual amount of estrogen is even further reduced. Dr. Cole says, "You're taking low estrogen and you're making it even lower. Now, why does that matter? Well, breast cancer cells that are hormone-sensitive can sense even those very small amounts of estrogen."Patients are still being enrolled in the trial. Researchers across the country will enroll 3,000 postmenopausal women who have received at least five years of tamoxifen therapy. Dr. Cole says, "Tamoxifen is a different type of medication. It blocks the receptors for estrogens on cancer cells." He says previous studies show aromatase inhibitors are at least equivalent, if not superior, to tamoxifen. He says, "It seems as though lowering the estrogen levels is even more effective than blocking estrogen interaction with cells in post-menopausal patients."
Dr. Cole says, even after five years of cancer-free status, there still is an ongoing risk of breast cancer recurrence. He says about 20 percent of patients in some groups will have recurrences after five years. He tells Ivanhoe that this is the first trial of this kind in this setting but says the results in terms of effectiveness are years away. "It will take a while before there is enough follow-up to be able to have enough recurrences to make a statement." He is optimistic about the efficacy of exemestane and says, "Our goal is to increase the number of patients who are cured from breast cancer by preventing a recurrence. Anything that prevents recurrences is going to increase cure."
