Breast Cancer News:

Study: Women Who Take Tamoxifen for Breast Cancer Have a Slightly Higher Risk of Stroke

Tamoxifen appears to slightly increase the risk of stroke in women who use this commonly prescribed breast cancer drug, according to a study reported in the October 12 issue of Neurology.

Despite their finding, Duke University Medical Center researchers emphasize that this does not mean that the use of tamoxifen should be reduced, given the drug's considerable benefits. Rather, they say, it means that women should be screened for possible stroke risk before the drug is prescribed for them.

Tamoxifen is known to increase the risk of thromboembolism or the blockage of a blood vessel by a blood clot. As a result, researchers believe that tamoxifen could theoretically be associated with higher risk of arterial obstruction in the brain and could cause ischemic stroke.

The researchers reviewed studies conducted on tamoxifen since 1980 in which it was compared with a placebo or other breast cancer therapy. The average age of women enrolled in the studies ranged from 47 to 65 years. All of the studies used a standard dose of 20 milligrams per day of tamoxifen.

The researchers found the absolute risk of stroke with tamoxifen of 0.71 percent over an average study follow-up of five years, a common duration of treatment with this medication, while control groups experienced 0.39 percent increase in absolute risk of stroke.

The frequency of all strokes was 1.06 percent with tamoxifen versus 0.76 percent in controls. An estimated yearly ischemic stroke risk with tamoxifen was determined to be 0.053 percent versus 0.035 percent in controls.

"This equates to roughly seven women in 1,000 who experienced a stroke during the five years they were taking tamoxifen," said study author Cheryl Bushnell, M.D., a neurologist at Duke. "The overall risk is equal to approximately five women in 10,000. From my estimates, 313 women would need to take tamoxifen for five years before a stroke occurred in any of them.”

Although the risk is very small, Bushnell said it is still very important, noting that the findings support the practice of careful screening of women being considered for tamoxifen therapy, particularly women who are older.

In many women, the risk of stroke with tamoxifen may outweigh the benefit of treating or preventing breast cancer,” Bushnell added. “Women should not stop their prescribed therapy based on these findings."

Source: Medical Week staff, week of October 16, 2004