First North American trial to evaluate the role of an aromatase inhibitor in the prevention of breast cancer

Mar 30 2005

Today, a new clinical trial evaluating a novel approach to breast cancer prevention launched in the United States and Canada. Called the ExCel research study, this is the first North American clinical trial to evaluate the role of an aromatase inhibitor in the prevention of breast cancer.

Coordinated by the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG), the ExCel research study will examine the potential benefit of exemestane and its ability to prevent breast cancer in women who are at increased risk for the disease. Exemestane -- part of a class of drugs called aromatase inhibitors -- suppresses estrogen production, a key component in the development of some types of breast cancer. Exemestane could provide women with an alternative option to tamoxifen, the only drug FDA approved for prevention of breast cancer.

"Breast cancer is a major public health issue -- every 30 seconds somewhere in the world a woman is diagnosed with this disease," says Dr. Paul Goss, the ExCel research study chair. "Thousands of women have already beat breast cancer thanks to recent research on aromatase inhibitors. As a result, we think this could be an effective approach to preventing it from developing in the first place."

The ExCel research study will follow more than 4,500 postmenopausal women from the U.S., Canada and Spain over a five year period. To be eligible, women must be 35 years of age or older and have an increased risk of developing breast cancer. Risk factors can include a woman's age, her family history of breast cancer, her age at first menstrual period and her age at first live birth.

Initial results of the trial could be available within four years and study investigators hope to see as much as a two-thirds reduction in the incidence of breast cancer among women in the treatment group.

Aromatase inhibitors are currently being used to treat breast cancer in women around the world and results from a study published in a March 2004 issue of the New England Journal of Medicine demonstrated that exemestane can prevent the occurrence of new cancers in the opposite breast of women who have already had breast cancer, suggesting that it may also be able to prevent the disease in healthy women.

Clinical studies have also shown that aromatase inhibitors are associated with fewer serious side effects than tamoxifen, the only other drug available to women for primary breast cancer prevention.

"While tamoxifen has already been shown to reduce the incidence of primary breast cancer, many women choose not to take this drug because of its known side effects," says Dr. Goss, also Director of Breast Cancer Research at the Massachusetts General Hospital and Professor of Medicine at Harvard Medical School. "Results of this study will provide women with important information about another potentially effective tool for breast cancer prevention."

Women enrolled in the ExCel research study will be randomized to one of two groups and all will take one pill per day for five years. Group A will take exemestane and Group B will take a placebo. Women will participate in two follow-up visits during the first year -- at six and 12 months -- and then an annual follow-up visit during years two through five.

Women will have a screening visit with a member of the study's clinical staff to see if they are eligible for the trial. If eligible, they will undergo a routine health examination, routine blood tests, a mammogram and a bone mineral density test.

The National Cancer Institute of Canada Clinical Trials Group (NCIC CTG), based at Queen's University in Kingston Ontario, is working in cooperation with physicians in Canada, the U.S. and Spain to coordinate the ExCel research study.

Founded in 1971 and funded by the Canadian Cancer Society, the NCIC CTG develops, conducts and analyzes national and international trials of cancer therapy, including trials for new cancer drugs, cancer prevention and supportive care to improve quality of life for people with cancer. Since its inception, the NCIC CTG has enrolled more than 40,000 patients from Canada and around the world in over 300 clinical trials.