Many women who’ve had breast cancer or are at high risk for the disease take tamoxifen for years. A new study now shows that long-term tamoxifen use seems to increase the risk of stroke, although the absolute increase in risk is small.

Drs. Cheryl D. Bushnell and Larry B. Goldstein, physicians at Duke University Medical Center in Durham, North Carolina, theorize in the medical journal Neurology that tamoxifen increases the risk of blood clots and therefore stroke.

It has been recommended that tamoxifen be avoided in women with a history of stroke, transient ischemic attack (sometimes called a mini-stroke) or venous thrombosis, the team notes.

This prompted the researchers to review all clinical trials of tamoxifen for the treatment or prevention of breast cancer published since 1980. They identified nine studies that reported stroke-related findings after a minimum follow-up of 1 year.

Their analysis included some 39,000 subjects, about half of whom were randomly assigned to take tamoxifen.

Six trials specifically reported strokes caused by blockages of blood-flow to the brain, and these occurred in 0.71 percent of those taking tamoxifen and 0.39 percent of the comparison group.

Therefore, the absolute increase in risk for these types of stroke was 0.32 percent, and the estimated yearly absolute increase in risk was 0.018 percent - meaning that 18 of every 100,000 women taking tamoxifen could be expected to suffer a stroke during a 1-year period because of the drug.

These results “support the practice of careful screening of women who are being considered for tamoxifen therapy,” Bushnell and Goldstein conclude. However, they also point out that “physicians and their patients should be reassured that the absolute risk of stroke may be low.”

SOURCE: Neurology, October 12, 2004.