Results from a recent clinical trial confirm those of previous clinical trials
indicating that exemestane may prolong survival and cause fewer side effects compared to megestrol acetate in the treatment of post-menopausal breast cancer patients who are no longer responding to tamoxifen.
Estrogen receptor (ER) positive breast cancer is a type of cancer that is stimulated to grow by a naturally occurring female hormone called estrogen. Specific proteins called estrogen receptors cover the surface of these cancer cells, enabling estrogen to enter into the cell and ultimately facilitating cancer growth. Historically, women with ER positive breast cancer were treated with a drug called tamoxifen, which blocks estrogen from entering into a cell, thus eliminating its source for growth. For patients whose cancer has stopped responding to tamoxifen, the standard of care was treatment with a drug called megestrol acetate. Recently, however, new forms of hormonal therapy have been developed and approved by the Food and Drug Administration (FDA) for treatment of ER positive breast cancer. These agents, referred to as aromatase inhibitors or inactivators, are beginning to replace tamoxifen and megestrol acetate in the clinical setting.
Aromatase inactivators work by irreversibly binding to a protein called aromatase, which ultimately blocks the entire conversion process that is responsible for creating the active form of estrogen. This reduces levels of the active form of estrogen in the body so that cancer cells are depleted of their necessary growth stimulant. Exemestane is an aromatase inactivator that has been approved by the FDA for use in post-menopausal breast cancer patients who have stopped responding to tamoxifen.
Recently, a clinical trial was conducted to directly compare exemestane to megestrol acetate in the treatment of women who have stopped responding to tamoxifen. All patients in this trial were post-menopausal with advanced breast cancer. They received treatment with either exemestane or megestrol acetate. Overall survival time for patients treated with exemestane has not yet been reached. Overall survival time for patients treated with megestrol acetate was approximately 2.5 years. Importantly, patients treated with exemestane reported an improved quality of life over those treated with megestrol acetate.
These results confirm those of previous clinical trials indicating that exemestane produces superior results and enhances quality of life over megestrol acetate in patients who have failed therapy with tamoxifen. As a result of this and previous studies, exemestane is currently being evaluated as initial treatment for post-menopausal women with ER positive breast cancer. Patients with ER positive breast cancer may wish to speak with their physician regarding the use of exemestane. (
Journal of Clinical Oncology, Vol 18, No 7, pp 1399-1411, 2000)
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