There has been ongoing debate about how to treat these tumors, according to Isaacs. The new study, she said, "adds support to the notion to consider" further treatment.
In other findings reported at the meeting, changes in breast density during treatment with tamoxifen, a drug often used to lower breast cancer risk, can help predict how well the drug is working, said Jack Cuzick, head of the Cancer Research UK Centre for Epidemiology, Mathematics and Statistics in London.
He evaluated more than 7,000 participants involved in the International Breast Intervention Study I, assessing their breast density after 12 to 18 months of tamoxifen treatment or placebo treatment, then looking at breast cancer risk.
For the 46 percent of women in the tamoxifen arm whose density was reduced by 10 percent or greater, the risk of breast cancer declined by 52 percent compared to the control group getting placebo. The risk of breast cancer declined by just 8 percent in the 54 percent of women whose density was not reduced by 10 percent.
Breast density is easy and simple to measure on a mammogram, he said, and a useful predictor of breast cancer risk. Now, based on his findings, it's also a good predictor of response to tamoxifen.
Isaacs called that finding valuable. Being able to identify whether a woman is benefiting from the tamoxifen early will allow her physician to consider other treatments, she said.
To learn more about cancer terms, visit the U.S. National Cancer Institute.
SOURCES: Dec. 12, 2008, teleconference with Ana M. Gonzalez-Angulo, M.D., researcher, University of Texas M.D. Anderson Cancer Center, Houston; Claudine Isaacs, M.D., director, clinical breast cancer program, and associate professor, medicine, Georgetown University Med
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