Tamoxifen Benefit Even After Therapy
Pill Continues to Prevent Breast Cancer, With Fewer Side Effects
Dec. 19, 2006 (San Antonio) -- Tamoxifen cuts the risk of breast cancer in some women by about a third, a new
study confirms, and the benefit persists even after treatment ends.
Meanwhile, "many serious side effects that were apparent during active
treatment disappeared over time," says researcher Jack Cuzick, MD, of
Cancer Research UK in London.
Initial results of the trial, released in 2002, showed that five years of
tamoxifen therapy prevents the type of breast cancer that needs estrogen to
These new results provide "the clearest evidence to date that you get
benefit even after stopping tamoxifen," says Powell Brown, MD, PhD, a
breast cancer specialist at Baylor College of Medicine in Houston.
Brown, who was not involved with the study, moderated the session where the
research was presented at the 29th Annual San Antonio Breast Cancer
Tamoxifen and Breast Cancer Risk
The study looked at 7,145 women at high risk of developing breast cancer
because they had either a mother or a sister who developed the disease before
age 50, other family history of breast cancer, or a previous noncancerous
The women took either a tamoxifen pill or a placebo for a period of five
years between 1992 and 2001.
By a median eight years later, 87 women on tamoxifen vs. 129 women on the
placebo had developed cancers fueled by estrogen.
Those numbers translate to a 34% reduction in risk for the women on
"More than 10 years out, the risk reduction is quite consistent with
what we saw at five years," Cuzick says.
Tamoxifen did not help prevent the type of tumors not fueled by estrogen,
which are notoriously difficult to treat, he says.
Also, while many doctors had thought tamoxifen could prevent breast cancer
in women taking hormone replacement therapy (HRT), that did not prove to be the
"The data do not support the hypothesis that you can prevent HRT-related
breast cancers by giving tamoxifen," he tells WebMD.
Tamoxifen Side Effects Dissipate
Cuzick says many common side effects -- including headaches, abnormal
bleeding, and hot flashes -- virtually
disappeared after stopping tamoxifen.
Tamoxifen is also known to cause potentially dangerous blood clots. However,
by a median eight years after stopping treatment, women on tamoxifen were no
more likely to have clots than those on a placebo.
Similarly, tamoxifen increased the risk of uterine
cancer during active treatment. But after stopping therapy, women who
had taken tamoxifen were slightly less likely to develop uterine cancer than
those on placebo.