Breast cancer patients who double the length of time that they take a common medication can sharply reduce their risk of death, according to a new study that's predicted to influence medical practice.
The study involved an estrogen-blocking pill called tamoxifen, a standard hormonal therapy for the roughly two-thirds of breast cancer patients whose tumors are sensitive to estrogen. Taking tamoxifen for five years after diagnosis reduces breast cancer mortality by about one-third.
In the study, women with early tumors who took tamoxifen for 10 years cut their risk of dying from breast cancer by an additional 29%, compared with women who stopped after five. In absolute terms, 12% of women on tamoxifen for 10 years died of breast cancer within five to 14 years after diagnosis, compared with 15% of those who stopped at five.
Overall, women who take tamoxifen for a decade cut their risk of dying from breast cancer nearly in half, compared with those who don't take it at all, says study co-author Richard Gray of the University of Oxford in the United Kingdom.
That's significant, given that tamoxifen is used by hundreds of thousands of women worldwide, says Gray, whose study was presented Wednesday at the annual San Antonio Breast Cancer Symposium. Oxford funded the study, which included more than 6,800 women from 36 countries.
"This is a dream come true for women," says V. Craig Jordan, a researcher who led tamoxifen's development but who wasn't involved in the new study. "It's very exciting," he says, and likely will quickly change care for some women.
Tamoxifen, used for decades, is far cheaper than most new chemotherapies and biological drugs, which cost thousands of dollars a month. A generic version costs about $100 a month in the USA, according to Susan G. Komen for the Cure.
Younger women with more aggressive tumors may want to extend their tamoxifen use, says Jennifer Litton, an assistant professor at M.D. Anderson Cancer Center in Houston, who wasn't involved in the study.
Tamoxifen is the only hormonal option for women before menopause, Litton says. Doctors may not want to change the care of older patients, however, she says. That's because postmenopausal women have the option of tamoxifen or another class of hormonal therapies called aromatase inhibitors, or AIs. These drugs are slightly more effective than tamoxifen, although they don't work before menopause, Litton says.
Because the study didn't include AIs, doctors can't say whether tamoxifen would benefit women who have taken them, Litton says. Researchers are conducting trials comparing five vs. 10 years of AIs, though results won't be out for several years.
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