Tamoxifen, Cholesterol and Heart Health

Studies have shown that the breast cancer drug tamoxifen also has a positive impact on cholesterol levels. But at least in the short term, the drug does not appear to protect against heart disease, according to results from the Breast Cancer Prevention Trial (BCPT).

Writing in the Journal of the National Cancer Institute, Dr. Steven Reis of the University of Pittsburgh Medical Center and colleagues reported results from the BCPT showing that tamoxifen taken by women at high risk of breast cancer reduced the chance of developing breast cancer by about half.

However, in addition to looking at tamoxifen's effect on breast disease, the researchers conducting the BCPT trial followed the 13,388 participants to see whether the drug had any affect on heart health. After an average follow-up of 49 months, they found no significant difference in the rate of heart attacks and serious chest pain events (angina) between the tamoxifen group and the placebo group. The finding held true whether or not the women had a history of heart disease.

Tamoxifen was expected to decrease a woman's risk of heart disease because it acts similarly to the hormone estrogen in its ability to raise or lower cholesterol levels. Both estrogen and tamoxifen reduce "bad" cholesterol (low-density lipoprotein or LDL), and increase "good" cholesterol (high-density lipoprotein or HDL).

The finding that tamoxifen does not protect the heart suggests that the cholesterol-lowering ability of the drug is not an accurate marker for heart disease, the study's authors wrote.

Further study will be needed, said Reis. "Because tamoxifen is being prescribed increasingly for the prevention and treatment of breast cancer, longer term clinical trials of tamoxifen in women are needed to further elucidate its long-term cardiovascular effects."

In an accompanying editorial, V. Craig Jordan, Ph.D., of Northwestern University Medical School, said that important issues have yet to be addressed. "We need to discover why estrogen can successfully prevent osteoporosis but its beneficial effect on coronary heart disease is much harder to demonstrate," he wrote.

More heart-disease information will eventually be produced from the STAR trial, which is comparing tamoxifen to the osteoporosis prevention drug raloxifene. Enrollment for that 22,000-woman study began in July 1999.

SOURCES:
Journal of the National Cancer Institute, January 3, 2001; 93:16-21
National Cancer Institute (http://www.nci.nih.gov)

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