Study on Use of Calcium Channel Blockers and Breast Cancer Risk in Postmenopausal Women in Cancer

American Cancer Society
Friday, 24 October 1997

An epidemiologic study in the October 15, 1997 issue of the American Cancer Society journal Cancer suggests that postmenopausal women who take calcium channel blockers (a class of drugs used to control high blood pressure) may be at increased risk for breast cancer. Researchers from the University of Washington, Seattle, studied 3,198 women ages 65 to 100 who were enrolled in The Cardiovascular Health Study (a multisite study funded by the National Heart, Lung and Blood Institute) and found that women who had taken calcium channel blockers were more than twice as likely to develop breast cancer than other women. According to the researchers, calcium channel blockers could contribute to tumor growth by interfering with normal cell death (apoptosis).

Among the study group, 75 women developed breast cancer; of those women, 20 took calcium channel blockers to control high blood pressure. Risks were not elevated for women taking other blood pressure medications, such as beta blockers or diuretics. The researchers conclude that further investigation is needed, and caution that women should not stop taking their blood pressure medication based on the results of this study.

The National Institutes of Health released the following statement today: "The National Heart, Lung and Blood Institute (NHLBI), National Cancer Institute and National Institute on Aging, all units of the National Institutes of Health, want to urge patients not to stop taking a calcium channel blocker without consulting their physician. Officials at these institutes note that the dangers of uncontrolled high blood pressure may outweigh a possible cancer risk found in the study."

"Last year it was first suggested that calcium channel blockers might increase cancer risk," says Clark Heath, Jr., MD, vice president of Epidemiology and Surveillance Research for the American Cancer Society. "This new study supports those initial findings, at least with respect to postmenopausal breast cancer. Such research, however, is still in its early phases, so firm conclusions are premature. Future work needs to examine larger study populations, other cancer sites, and possible dose-related interactions with other cancer risk factors," says Dr. Heath.

For more information, or to contact American Cancer Society, see their website at: www.cancer.org