WEDNESDAY, Oct. 20, 2004 (HealthDayNews) -- Taking tamoxifen to treat breast cancer won't increase your risk of stroke.
However, a report on that finding, which appears in the Oct. 20 issue of the Journal of the National Cancer Institute, did conclude that chemotherapy can raise the odds of a brain attack.
"The bottom line from this study is when we looked at women who had a first stroke after their breast cancer diagnosis, we did not see a relationship between tamoxifen and stroke," said study co-author Ann Geiger, group leader in cancer research at Kaiser Permanente Southern California in Pasadena.
Tamoxifen is a drug sometimes called an anti-estrogen because it interferes with estrogen activity that can help breast cancer cells grow. Tamoxifen has been used for more than 20 years as a treatment for breast cancer, and many women who are at high risk for breast cancer use tamoxifen today to try to prevent the disease.
Previous studies had shown that tamoxifen could increase a woman's risk of stroke. According to Geiger, however, these studies didn't independently confirm the stroke diagnosis and they didn't control the data for the participants' other risk factors for stroke.
So Geiger and her colleagues enrolled more than 11,000 women from Los Angeles County who had been diagnosed with breast cancer to assess the risk of stroke from tamoxifen treatment.
All of the women had been diagnosed between 1980 and 2000, and all were members of Kaiser Permanente, a large health maintenance organization.
The researchers gathered information on the breast cancer treatments given, tumor characteristics, height, weight, histories of diabetes, high blood pressure and high cholesterol. The researchers also gathered information on reproductive history, birth control use, and smoking history.
Four hundred and twenty-two women were found to have had possible strokes. Forty-nine of those were excluded because the stroke occurred before the breast cancer diagnosis. Another 194 from that group were deemed ineligible either because their stroke could not be confirmed or the researchers couldn't gather sufficient tamoxifen information.
That left 179 women with confirmed strokes after their breast cancer diagnosis. The researchers then compared these women to 431 control patients who were age-matched and had similar breast cancers.
The researchers found no association between tamoxifen use and stroke. Instead, they discovered that chemotherapy more than doubled a woman's stroke risk. It didn't seem to matter what chemotherapy regimen a woman had undergone; all appeared to increase stroke risk.
Geiger was quick to point out, however, "that the overall risk of stroke is very low compared to the known benefits of chemotherapy."
Dr. Jay Brooks, chief of hematology/oncology at Ochsner Clinic Foundation Hospital in New Orleans, said that because chemotherapy kills rapidly dividing cells, it may "rough" them up and make blood clots more likely.
The researchers weren't sure why chemotherapy might increase stroke risk. They speculated that women who had chemotherapy might have had more advanced or more persistent cancer that can increase the risk of blood clots. Or some of the drugs given to help control the side effects of chemotherapy might play a role, Geiger added.
"I think if women are considering tamoxifen, they and their clinicians probably don't need to be worried about stroke risk. Women who have had chemotherapy probably will want to manage their stroke risk as best they can by controlling blood pressure and cholesterol and watching their diet and exercising," Geiger said.
"I think this study is reassuring for patients on tamoxifen, but it is in conflict with some of the other studies that found the risk of stroke in patients on tamoxifen is increased, but relatively low," Brooks said.
"I tend to shy away from tamoxifen in patients with an increased risk of cardiovascular disease because of the availability of other agents that prevent the return of breast cancer," Brooks added.
More information
To learn more about tamoxifen, go to the National Cancer Institute.
