Exemestane Gives New Hope to High-Risk Postmenopausal Women

LONDON, ON - Approximately 1.3 million women worldwide are diagnosed with breast cancer each year, and nearly 500,000 women die of the disease. Postmenopausal women are at particularly high risk, with 80% of breast cancers occurring in women over age 50. Preventative medications are available, but their potential for serious side effects has deterred women and their doctors from using them. Fortunately, the results of a new clinical trial suggest there may be a safer alternative. According to Dr. Eric Winquist, Lawson Health Research Institute, exemestane can reduce the risk of developing breast cancer by 65 per cent amongst postmenopausal women.

Breast cancer is believed to thrive on estrogen. Available anti-estrogen medications have been shown to reduce the risk of breast cancer, but have also been associated with rare but serious uterine cancer and potentially fatal blood clots. Exemestane is an oral aromatase inhibitor (AI) that prevents the synthesis of estrogen and lowers the level of this hormone in the body. Since exemestane provides the same powerful benefits as anti-estrogens without the serious toxicities, Dr. Winquist and his colleagues believed it might work equally well for breast cancer prevention. Through the international ExCel study, they tested this theory.

To assess exemestane as a breast cancer preventative, the ExCel group conducted a large randomized double-blind clinical trial. A total of 4,560 postmenopausal women from Canada, the United States, Spain, and France were enrolled, with London as the highest enrolling Canadian centre. Patients were split into two groups, one taking 25 mg of exemestane and the other a matching placebo, once daily for five years. At three-years of follow-up, results indicated exemestane reduced invasive breast cancers by 65 per cent. Patients taking exemestane also developed fewer cases of precancerous breast findings known to have a higher risk of progressing to breast cancer.

Overall, exemestane’s side effect profile was excellent. Symptoms such as hot flashes, fatigue, sweating, insomnia, and joint paint were only slightly more common amongst women on exemestane. Dr. Winquist and his colleagues noted; however, that this did not affect patients’ self-reports of overall health-related quality of life. More serious symptoms, such as bone fractures, osteoporosis, adverse cardiovascular events and other non-breast cancers, were equally common in both groups. The research institute of London Health Sciences Centre and St. Joseph’s Health Care, London.

“Although the follow-up period is short at this point, these results have very exciting potential,” Dr. Winquist says. “For postmenopausal women at a higher risk for developing breast cancer, exemestane appears to be a highly effective drug therapy option with, on average, only mild side effects.

ExCel was led and coordinated by Canada’s NCIC Clinical Trials Group (NCIC CTG), with whom Dr. Winquist is an investigator. Moving forward, study participants receiving placebo will have the opportunity to receive exemestane for five years.

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Lawson Health Research Institute. As the research institute of London Health Sciences Centre and St. Joseph's Health Care, London, and working in partnership with The University of Western Ontario, Lawson Health Research Institute is committed to furthering scientific knowledge to advance health care around the world. www.lawsonresearch.com

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Sonya Gilpin
Communications & Public Relations
Lawson Health Research Institute
519-685-8500 ext. 75852
sonya.gilpin@lawsonresearch.com
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