November 15, 2005
Study shows tamoxifen can prevent cancer for years
By Susan Heavey
WASHINGTON (Reuters) - Women at high risk for breast cancer
who take the well-known drug tamoxifen can reduce their
long-term risk of developing the disease, according to a new
study released on Tuesday.
Researchers found that women who took tamoxifen, sold as a
generic and by AstraZeneca Plc under the brand Nolvadex, for up
to five years were about 43 percent less likely to get breast
cancer than those who took a placebo.
Out of 6,681 women taking the drug, 145 have developed
cancer since the study began in 1992, compared with 250 cases
in 6,707 women assigned to placebo, according to scientists at
the Pittsburgh-based research network that conducted the trial
with funding from the National Cancer Institute.
"This final analysis confirms that tamoxifen reduces the
risk of invasive breast cancer in both pre- and post-menopausal
women at increased risk for the disease," they said in a
While a number of new medicines have been shown to treat
the disease, such as Genentech Inc. and Roche's Herceptin and
others, only tamoxifen has U.S.-approval to prevent it in
Researchers at the National Surgical Adjuvant Breast and
Bowel Project network studied women at least 60 years old or
who were between ages 35 and 59 with a high risk, such as
having an mother or sister who had been diagnosed or
experiencing breast lumps that were then tested.
About 17 out of every 1,000 women who are over 60 may
develop the disease within five years, they said.
Breast cancer is one of the leading cancers among U.S.
women. More than 200,000 are diagnosed and another roughly
40,000 die from it each year, according to the American Cancer
Some women took the drug for up to five years, others for
less time before researchers told participants in 1998 if they
were taking tamoxifen and allowed them to opt for the drug. At
that time, findings showed it could reduce cancer risk by 49
percent, and researchers have continued to follow the patients.
"There is proof of a benefit from tamoxifen beyond the time
a woman is taking the pills," said Dr. Leslie Ford, co-author
of the study and associate director for NCI's Division of
They also found women taking tamoxifen experienced fewer
broken bones than those taking placebo. Eighty women on the
drug reported a hip, wrist or spine fracture compared with 116
reports from those on the placebo.
The earlier results also found tamoxifen increased the risk
of cancer in the uterus lining as well as blood clots in the
lungs and major veins. These new findings showed no
statistically significant change, researchers said, although
the rate of lung blood clots was 11 percent lower and uterine
cancer was about 29 percent higher than in 1998.
Other possible side-effects, including stroke and
cataracts, remained about the same as long as patients did not
take the drug longer than five years, which could increase
possible problems, researchers said.
The group is also studying tamoxifen's ability to prevent
the disease in comparison to raloxifene, an osteoporosis drug
sold under the brand Evista by Eli Lilly and Co.. Those results
are due next spring.
European researchers are also studying AstraZenaca's new
breast cancer treatment Arimidex, or anastrazole, for
Like tamoxifen, both drugs also work by blocking the