Tamoxifen Decreases Heart Disease
Five Years of Breast Cancer Drug Best for Added Benefit
Nov. 2, 2004 (Vienna, Austria) -- Women who take the breast cancer drug tamoxifen may be getting a bonus: The medication also appears to lower the risk of dying from heart disease, Swedish researchers report.
A new study shows that women who have taken tamoxifen for five or more years to treat breast cancer are one-third less likely to die of heart disease than those who took the drug for only two years, says Bo Nordenskjold, MD, a professor of oncology at Linkoping University in Linkoping, Sweden.
Heart disease is the No. 1 killer of women in the industrialized world, Nordenskjold notes.
"It's good to know that tamoxifen, which is used not only to treat breast cancer but also to prevent it in high-risk women, also reduces the chance of death from heart disease," he tells WebMD.
The findings were presented at the European Society for Medical Oncology Congress.
Five Years of Tamoxifen Optimal
Nordenskjold is well known in scientific circles: In the mid-1990s, he and other researchers with the Swedish Breast Cancer Group reported the landmark study that established that the optimal length of tamoxifen for treating breast cancer in post-menopausal women is five years.
"In 1994, we showed that postmenopausal women with breast cancer who were given the drug for five years lived longer than those given the drug for two years" -- a finding that led to five years of therapy becoming standard practice, he says. "And now we have shown that five years of treatment is optimal for the heart as well."
To arrive at the new findings, Nordenskjold and colleagues determined the causes of death among the 1,180 women who had died since being enrolled in the original breast cancer study.
"Following up on these women seven to eight years after they started tamoxifen therapy allowed us to make observations that weren't immediately apparent," Nordenskjold says.
The study showed that the women who took tamoxifen for at least five years were 33% less likely to die from coronary heart disease compared with those who got the drug for two years, he says. The researchers did not look at whether taking tamoxifen reduced the risk of death compared with never taking the drug, only at whether five years of treatment was better than two.
Women who took the drug for five years were slightly more likely to die of endometrial cancer (cancer of the uterus) than those who took it for the shorter time period, but the numbers were so small they could have been due to chance, Nordenskjold notes.
While the study was not designed to look at how tamoxifen protects against heart disease, Nordenskjold attributes its heart-healthy effect to the fact that the drug, in part, mimics the effects of estrogen.
"Tamoxifen is a weak estrogen compared with natural estrogen, but it is an estrogen," he tells WebMD. "And estrogen protects against heart disease."
Heart disease risk increases dramatically in women after menopause because of the loss of estrogen.