WEDNESDAY, Dec. 5 (HealthDay News) --Taking the breast cancer
drug tamoxifen for a decade, instead of the standard five years,
further reduces the long-term chances of recurrence and risk of
dying from the disease, new British research suggests.
The increase in benefit is especially noticeable after the 10th
year, said study author Richard Peto, a professor of medical
statistics and epidemiology at the University of Oxford.
Tamoxifen is widely used for treating estrogen receptor or
ER-positive breast cancer in women who are pre-menopausal.
ER-positive cancers need estrogen to grow, and the drug blocks the
activity of estrogen in the breast.
Currently, tamoxifen is usually given daily for five years after
a cancer is treated. Doctors have known that five years is more
effective than two, and that it reduces the rate of death from
breast cancer by about a third in comparison to not taking it, and
that it does so for 15 years after the diagnosis.
In the new study, the researchers wanted to see if longer
treatment would be even better. They compared results in women who
took tamoxifen for five years and 10 years.
A decade was better.
"It's been one moderate therapeutic advance after another," Peto said.
The new research is to be presented Wednesday at the San Antonio
Breast Cancer Symposium and published simultaneously in
In the new study, Peto's team looked at nearly 13,000 women who
had already taken the drug for five years.
The women were assigned to continue the drug for another five
years or to stop taking it. For the analysis, the researchers
focused on the 6,846 women who had ER-positive breast cancer, as
the main benefit of tamoxifen is thought to be for them. Of these,
about half kept taking the drug and half did not.
After about eight years of follow-up, there were 617 recurrences
in the drug group and 711 in the group that had stopped. While 331
in the drug group died of breast cancer during follow up, 397 in
the group that stopped died.
The risk of breast cancer death five to 14 years after the
diagnosis was slightly over 12 percent among those who stayed on
the drug versus 15 percent among those who stopped.
The follow-up is continuing, Peto said. "We are going to follow
for another five years, to see what happens," he said. "I think
there will probably be future gain."
Will tamoxifen end up being a lifetime drug, once it is
prescribed? "No, because tamoxifen has side effects," Peto
The side effects are well documented -- an increased risk of
cancer of the uterus and blood clots in the lungs are major ones.
In the study, those who continued on the drug had higher risks of
both conditions. However, the risks were outweighed by the
reduction in death risk, the researchers added.
The research will be practice-changing, said Dr. Joann Mortimer,
director of the Women's Cancers Program at City of Hope
Comprehensive Cancer Center, in Duarte, Calif.
"Whether women will allow it to change practice remains to be seen," she said, referring to the reluctance of women to take anti-cancer drugs like tamoxifen. Compliance is ''atrocious," she said.
Women stop the drug for many reasons, she said, including side
Even so, she said, the new research is reason enough for women
who may benefit from tamoxifen to talk to their doctor about it,
The study was funded by AstraZeneca, which makes tamoxifen, as
well as Cancer Research U.K., Medical Research Council, the U.S.
Army and the European Union.
To learn more about tamoxifen, visit the
U.S. National Library of Medicine.
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