WEDNESDAY, Jan. 15, 2003 (HealthDayNews) -- For women who have an increased risk of developing estrogen-dependent breast cancer, preventive therapy with tamoxifen can significantly reduce their chances of getting the disease, according to an Italian study.
The study, which appears in today's issue of the Journal of the National Cancer Institute, found that high-risk women who took tamoxifen for more than five years decreased their risk of cancer by as much as 82 percent.
"High-risk women are deriving substantial benefit from tamoxifen for risk reduction," says Dr. Victor Vogel, the director of breast cancer prevention at the University of Pittsburgh School of Medicine and co-author of an editorial accompanying the study.
Tamoxifen is a type of medication known as a selective estrogen receptor modulator. It is used both in cancer treatment and in prevention. Many types of breast cancer are dependent on estrogen for growth. Tamoxifen works by taking the place of estrogen in cancer cells, essentially crowding the estrogen out. Since tamoxifen acts only as a weak estrogen in breast cancer cells, it slows or prevents cancer cells from growing.
Tamoxifen, however, can also cause serious side effects, including a small increase in the rate of uterine cancer and the potential for blood clots, so it's not recommended for preventive use in the general population.
In this study, researchers from the European Institute of Oncology in Milan, Italy, compared the rates of breast cancer between 2,700 women who took tamoxifen therapy for more than six years and 2,700 women who took a placebo during that time.
The researchers only included women who had had hysterectomies (surgical removal of the uterus) in this study, so there wouldn't be a concern about the increase in the rate of uterine cancer.
Women who were taller than 5 feet 3 inches, who first menstruated before age 13, who had no children or who had their first child after the age of 24, and who still had their ovaries were classified as having a higher risk of estrogen-dependent breast cancer.
In these high-risk women, tamoxifen reduced the risk of breast cancer more than 80 percent. Also, women who had used hormone replacement therapy had a lowered risk of breast cancer if they took tamoxifen, according to the study.
For low-risk women, the researchers report no statistically significant difference between the tamoxifen and placebo groups. The authors theorize that these low-risk women may have other factors that protect them against cancer, and don't need added protection from tamoxifen.
"This study is good confirmation of another study," says Dr. David Decker, chief of hematology and oncology at Beaumont Hospital in Royal Oak, Mich. "Tamoxifen does prevent breast cancer. It works best in women who are destined to develop estrogen [dependent] breast cancer."
Some women definitely shouldn't take tamoxifen, according to Vogel. Women who are at a low risk of developing breast cancer shouldn't take tamoxifen. Women over 65 and anyone with a history of clotting should forgo the drug because they're already at an increased risk of developing blood clots.
The Italian researchers add that their findings are preliminary and need to be confirmed in other studies.
More information
To read more about the risks and benefits of tamoxifen, visit the National Cancer Institute or BreastCancer.org.
