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Back to Oncology Articles
Tuesday 25th July, 2006
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Only women at very high risk for breast
cancer experience a benefit according to a study
published in the journal Cancer.
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Most women at high risk for breast cancer do not increase
their life expectancy by taking the drug tamoxifen, according to
a new analysis by researchers from UC Davis, UCSF, the
University of Pittsburgh and McMaster University in Ontario,
Canada. In addition, the researchers showed that tamoxifen is an
extraordinarily expensive cancer-prevention strategy, costing as
much as $1.3 million per year of life saved. The study will be
published in the Sept. 1 issue of the American Cancer Society's
journal Cancer, and appear online on Monday.
"We found that for women at the lower end of the high-risk
range for developing breast cancer, there is a very small
likelihood that taking tamoxifen will reduce mortality," said
Joy Melnikow, professor of family and community medicine at UC
Davis School of Medicine and Medical Center and lead author of
the study. "This would support revising the current recommended
risk threshold for physicians to counsel women about tamoxifen."
Tamoxifen was approved by the U.S. Food and Drug
Administration in 1998 for breast cancer prevention in women who
have at least a 1.67-percent chance of developing the disease
over the next five years. Such women are considered at high risk
for breast cancer. Groups such as the U.S. Preventive Services
Task Force and the Canadian Task Force on Preventive Health Care
recommend that physicians counsel women above this threshold
about the benefits and risks of tamoxifen as a means of
preventing the disease.
Tamoxifen is a selective estrogen receptor-modulating drug
used to treat estrogen receptor-positive breast cancers. In
addition, it has been shown to reduce the incidence of invasive
breast cancer among high-risk women by up to 49 percent.
However, tamoxifen is associated with significant adverse
effects, including cataracts requiring surgery, deep vein
thromboses, endometrial cancer and stroke. Women taking
tamoxifen, if they do develop breast cancer, are also more
likely to develop an estrogen receptor-negative tumor, which has
a worse prognosis. (Cancers prevented by tamoxifen are mostly
estrogen receptor-positive).
In the new study, Melnikow and her colleagues calculate that
tamoxifen can be expected to extend life expectancy only when a
woman's five-year risk of developing breast cancer reaches 3
percent or more. This is especially true for women who have not
had a hysterectomy, and therefore face the risk of endometrial
cancer related to tamoxifen use.
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Cost-effectiveness was also calculated in the study. For women
at the 1.67-percent risk level, taking tamoxifen to stave off
breast cancer came to $1.3 million per year of life saved based
on the U.S. price of the drug -- a prohibitively expensive
cancer-prevention strategy. Melnikow and her co-authors note,
however, that the cost-effectiveness equation could be improved
if pharmaceutical prices were negotiated at a national level. At
Canadian prices, for example, the researchers showed that taking
tamoxifen to prevent breast cancer comes to $123,780 per year of
life saved for women at the 1.67-percent risk level.
In comparison, annual flu shots cost about $980 per year of
life saved for patients ages 65 and older; colonoscopy every 10
years costs about $11,000 per year of life saved for people 50
and older; and annual mammography costs about $58,000 per year
of life saved for women ages 40 to 80.
To arrive at their findings, Melnikow and her colleagues used
a complex mathematical model based on a hypothetical group of
50-year-old women.
Melnikow specializes in research to better understand women's
health-care preferences and how women make health-care
decisions. In a study published in the journal Cancer last year,
she reported that among women with a five-year breast cancer
risk of 1.67 percent or higher, fewer than one in five were
inclined to take tamoxifen to prevent the disease. Concern about
potential side effects was the primary reason.
Sources:
"Chemoprevention: Drug Pricing and Mortality: The Case of
Tamoxifen," Joy Melnikow, Christina Kuenneth, L. Jay Helms,
Amber Barnato, Miriam Kuppermann, Stephen Birch, James Nuovo,
CANCER; Published Online: July 24, 2006 (DOI:
10.1002/cncr.22075); Print Issue Date: September 1, 2006.
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