Tamoxifen Lowers Risk of Benign Breast Disease in Some Women
Key Words: benign, breast cancer, breast disease, tamoxifen. (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary.)
Women at high risk for breast cancer who took the drug tamoxifen were less likely to be diagnosed with benign (noncancerous) breast conditions than women at equal risk who took a placebo, according to a study published in the February 19, 2003, issue of the Journal of the National Cancer Institute (see the journal abstract of the study).
The results were initially presented prior to publication at the December 2001 San Antonio Breast Cancer Symposium.
Study participants were enrolled in the Breast Cancer Prevention Trial (BCPT), a large study that in 1998 found a 49 percent reduction in new cases of breast cancer among participants who took tamoxifen for five years. One of the unanswered questions about the results of that trial was whether tamoxifen really prevented breast cancer from developing or simply treated cancers that were too small to be detected.
Led by Elizabeth Tan-Chiu, M.D., of the Cancer Research Network in Plantation, Fla., researchers from the National Surgical Adjuvant Breast and Bowel Project examined the medical records of 13,203 women who took part in the BCPT. They also counted the number of biopsies performed on study participants.
Overall risk reduced 28 percent
They found that for women in the tamoxifen group, overall risk for developing benign breast disease was reduced by 28 percent. Women treated with tamoxifen had 29 percent fewer biopsies than women who received a placebo. The reduction in biopsies was seen predominantly in premenopausal women.
The new study results are good news for women at high risk for breast cancer, said Karen A. Johnson, M.D., of the National Cancer Institute's Division of Cancer Prevention. "These results suggest that tamoxifen is really working on early breast abnormalities that are associated with the subsequent development of breast cancer," she said. "They also suggest that tamoxifen may reduce the need for biopsies in high-risk women."
Women treated with tamoxifen had reduced rates of several benign breast diseases, including atypical hyperplasia, a condition in which noncancerous cells multiply to an abnormal extent.
Likely decrease in risk of future breast cancer
"There is good evidence that women who have atypical hyperplasia -- particularly if they have a family history of breast cancer -- are at increased risk of going on to develop invasive breast cancer," explained Johnson. "If you can reduce the incidence of atypical hyperplasia, that's likely to result in a decreased risk of developing invasive breast cancer in the future."
The new analysis clarifies our understanding of the overall balance of risk and benefit for women who are considering tamoxifen for breast cancer risk reduction, Johnson said. In the BCPT, women who took tamoxifen had a higher risk of developing blood clots and endometrial cancer than women who took a placebo. Women with an increased risk of breast cancer are advised to discuss the pros and cons of tamoxifen treatment with their health care provider.
The new findings may help to explain why tamoxifen prevents breast cancer, Johnson said. Tamoxifen works by blocking the effects of the hormone estrogen in the body. "These findings suggest that benign breast conditions are influenced by estrogen and that tamoxifen's disruption of the effects of estrogen leads to a reduction in these conditions. The results also support the idea that it's possible to intervene before an invasive cancer exists and prevent it from developing."
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