Breast cancer patients who double the length of time 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 therapy for the roughly two-thirds of breast cancer patients whose tumours are sensitive to estrogen. Taking tamoxifen for five years after diagnosis reduces breast cancer mortality by about one-third.
In the new study, women with early tumours who took tamoxifen for 10 years cut their risk of dying from breast cancer by another 29 per cent, compared to women who stopped after five years.
In absolute terms, 12 per cent of women on tamoxifen for 10 years died of breast cancer within five to 14 years after diagnosis, compared to 15 per cent of those who stopped at five years.
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, said study co-author Richard Gray of the University of Oxford in the United Kingdom.
That's significant, given tamoxifen is used by hundreds of thousands of women worldwide, said 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. While tamoxifen delays tumour growth in some women, it appears to cure others, Gray said.
"This is a dream come true for women," said V. Craig Jordan, a researcher who led tamoxifen's development, but wasn't involved in the new study. "It's very exciting."
Tamoxifen, which has been 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 U.S.
In the U.K., tamoxifen costs only $5 a month. In India, it's two cents a pill, said Jordan, scientific director at Georgetown's Lombardi Comprehensive Cancer Center.
Jordan said the new findings will quickly change care for some patients.
Younger women with more aggressive tumours may want to extend their tamoxifen use, said 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 said.
Doctors may not want to change the care of older patients, however, she said. 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 said.
Because the study didn't include AIs, doctors can't say how whether tamoxifen would benefit women who've taken them, Litton said. Other researchers are conducting trials comparing five versus 10 years of AIs, although these results won't be out for several years.
Gray noted tamoxifen has risks. In his study, doubling the length of treatment also doubled the risk of endometrial cancer, which affects the uterine lining, to about three per cent.
However, because this cancer is very treatable, death rates were low: 0.4 per cent of those on tamoxifen for 10 years died of endometrial cancer, compared to 0.2 per cent of those taking it for five years. Doctors saw no increase in strokes, which has long been a concern with tamoxifen, Gray said.
Breast cancer survivors have mixed reactions to the results.
Some women will be glad to have another treatment option, said breast cancer survivor Lillie Shockney, administrative director of the Johns Hopkins Cancer Survivorship Program in Baltimore.
"Patients get very nervous when they stop any hormonal therapy, because they feel like now they aren't doing anything," said Shockney. "The opportunity to 'do something' might be appealing, despite the side effects."
Shockney said she'd like to see research on other ways to prevent recurrences, such as weight loss. "If someone lost 40 pounds, would that do as much as another five years on tamoxifen?" Shockney asked.
Some patients may be reluctant to prolong their use of a drug that causes so many side effects, said Boston breast cancer survivor Alicia Staley.
Studies show only 80 per cent of women take tamoxifen for five years, Litton said. Some switch to an AI, although these drugs can also cause problems, such as joint pain and osteoporosis.
Staley said tamoxifen gave her "many, many side effects," including severe hot flashes. "Dry eyes, joint pain, weight gain -- you name it, I had it," she said. After 21/2 years, Staley and her doctor stopped the drug "to regain a measure of quality of life."
For Shockney, tamoxifen took a heavy toll on her marriage, causing dryness that made sex unbearably painful.
Patients and their partners need to have honest talks with doctors about how extended treatment will affect their relationship, she said.
-- USA Today