Tamoxifen, Evista Prevent Breast Cancer
Study Shows Tamoxifen Is a Little More Effective, but Evista May Have Less Risk
April 20, 2010 (Washington, D.C.) -- There are two good drug options for
preventing breast cancer in high-risk women, and more women need to take
advantage of them, doctors say.
Updated results from a large breast cancer prevention trial confirm that
both the old standby tamoxifen and the osteoporosis drug Evista can
substantially cut the risk of developing breast cancer in high-risk
Tamoxifen works a little better, but Evista may be a little safer, says
study head D. Lawrence Wickerham, MD, of Allegheny General Hospital in
But "only 5% to 20% of the tens of thousands of women" who could benefit
from the drugs use them, says Gabriel Hortobagyi, MD, a breast cancer
specialist at the University of Texas M.D. Anderson Cancer Center in Houston
who was not involved with the work.
Over 192,000 women, about 150,000 of whom were postmenopausal, were
diagnosed with breast cancer in 2009, he says.
Updated results from the STAR (Study of Tamoxifen and Raloxifene) trial were
presented at the annual meeting of the American Association for Cancer Research
and published online by the journal Cancer Prevention Research.
Tamoxifen has been used for years to help fight breast cancer's return. In
1998, the FDA approved tamoxifen for use by women who hadn't had breast cancer
but were at high risk of developing the disease.
Evista, known generically as raloxifene, is taken by about half a million
women in the U.S. to prevent and treat osteoporosis, or thinning of the bones.
In 2007, the FDA approved it for breast cancer prevention in some high-risk
postmenopausal women based on earlier results from STAR and other trials.
As a breast cancer preventive, they're recommended for women at
higher-than-average risk because of genetic mutations, family history, or other
factors, including age over 60.
Tamoxifen vs. Evista
The updated analysis of the federally funded study involved nearly 20,000
postmenopausal women followed for almost seven years during and after treatment
with either tamoxifen or Evista.
Earlier findings from the study, published in 2006, showed that both drugs
reduced the risk of breast cancer by about 50% in high-risk, postmenopausal
women. But Evista appeared to carry fewer risks of side effects, with lower
rates of uterine cancer and clotting problems.
The new findings suggest that several years after treatment, which lasts
about five years, tamoxifen is substantially better than raloxifene at
preventing breast cancer.
About two years after treatment ended, tamoxifen reduced the risk of
invasive breast cancer by 50%, while Evista cut risks by 38%.
Put another way, Evista was 76% as effective as tamoxifen, says Wickerham,
who serves as a consultant to makers of both drugs.
Evista was about 78% as effective as tamoxifen at preventing noninvasive
breast cancers (lobular carcinoma in situ and ductal carcinoma in situ).