Cure-all drug remains risky

The drug tamoxifen citrate not only helps prevent recurrence of breast cancer, but can keep the deadly disease from appearing in the first place in some women. However, a University of North Carolina at Chapel Hill study indicates that it remains unlikely that tamoxifen ever will be given widely to women to prevent breast cancer, as the drug would avert only a maximum of six to eight percent of breast tumors in eligible females.

"Our calculations showed that tamoxifen's possibly harmful side effects, including blood clots and stroke, would rule out some 90% of women who might benefit from taking it each day," states Russell P. Harris, associate professor of medicine. Tamoxifen works in women by blocking what is known as the estrogen receptor that allows the hormone to work. Most breast cancer development is dependent on estrogen.

The study had women--ages 40 to 69--in 10 general internal medicine practices fill out questionnaires about their health and family histories of breast cancer. Then, using a proven formula for assessing breast cancer incidence and factoring in the responses, researchers determined the expected number of cases that would occur over the next five years. They found that only a relatively small number of women in primary care practices would be eligible for the chemopreventive therapy because of existing conditions such as high blood pressure, diabetes, and other risk factors. Since a majority of females never develop breast cancer anyway, the percentage of actual cancers prevented would be small.

"Screening mammography, which is useful, is not the whole answer to preventing breast cancer deaths, and our new work shows that tamoxifen won't be either," Harris notes. "On the other hand, in a message to the research community, tamoxifen has shown us that if we can find other chemopreventive agents that don't have all the side effects, then we could have greater success and save more lives."

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