Study is part of the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial
PITTSBURGH, Jan. 2 -- The breast cancer prevention drug, tamoxifen, does not influence cardiovascular risk in healthy women or in women with coronary heart disease, according to a study published in the Jan. 3 Journal of the National Cancer Institute. The study, the largest clinical trial to assess the cardiovascular risk of tamoxifen, is part of the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial.
"We found that cardiovascular event rates were not statistically significantly different between women assigned to tamoxifen or placebo, independent of pre-existing coronary heart disease," stated Steven Reis, M.D., principal investigator in the study, associate professor of medicine at the University of Pittsburgh School of Medicine and director of the Women's Heart Center at UPMC Health System's Cardiovascular Institute. "These findings should provide a degree of comfort to those women who are taking tamoxifen for breast cancer prevention." Cardiovascular events included fatal and non-fatal myocardial infarction, unstable angina, and severe angina.
Between 1992 and 1997, 13,388 women at increased risk for breast cancer were randomly assigned to receive tamoxifen or a placebo. After four years, cardiovascular follow-up was available for 13,194 women. Of them, 1,048 had a prior history of clinical coronary heart disease such as heart attack or angina and 12,146 women reported no such history.
The study found that women who had coronary heart disease when they entered the study had a higher rate of cardiovascular events than the women without heart problems. However, within each group, there was no difference in the rate of cardiovascular events between those receiving tamoxifen and those receiving a placebo.
There were 72 cardiovascular events among the 6,604 tamoxifen users and 68 among the 6,590 women assigned to placebo. No differences were noted for fatal heart attack, nonfatal heart attack, unstable angina or severe angina.
Among the 12,146 women without a history of clinical coronary heart disease, there were a total of 96 cardiovascular events; 47 in the tamoxifen group and 49 in the placebo group.
Cardiovascular events for the 1,048 women with a prior history of clinical coronary heart disease also failed to show any statistically significant differences between the treatment groups.
"Although the event rates in the group of women with a prior history of heart disease are greater than those observed in the group of women without a history of heart disease, these data demonstrate that assignment to tamoxifen did not affect cardiovascular events in this high risk population," Dr. Reis reported. In this group, there were 25 cardiovascular events in the tamoxifen group and 19 in the placebo group.
"Because tamoxifen is increasingly being prescribed 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," Dr. Reis concluded.