New study data identify women most likely to benefit from tamoxifen as primary prevention of breast cancer
Women age 40-50 years with at least a 3.4-percent
five-year risk for breast cancer are most likely to benefit from
tamoxifen as primary prevention therapy, according to an article
in the September issue of Obstetrics & Gynecology. The same
study concluded that therapy is not cost-effective for women age
60-65 years unless they have a very high five-year risk (greater
than 5 percent).
Tamoxifen is the only drug approved in the
USA for primary prevention of breast cancer in women. However, there
has been debate over which women would most benefit from therapy
based on side effects including risk for deep vein thrombosis, pulmonary
embolism, stroke, and endometrial cancer.
In the current study, researchers examined
data from an earlier report that noted more than 10 million US women
are candidates for tamoxifen and at least 2 million of them would
experience a net benefit from the drug.
The authors drew five major points from analysis.
First, tamoxifen is cost-effective for every woman between the ages
of 40-50 years who has at least a 3.4% five-year risk of breast
cancer. In addition, tamoxifen may be justified in 40-year-old women
who have a baseline five-year risk as low as 1.5 percent.
The researchers also drew conclusions on usage in older women.
For women age 60-65 years, tamoxifen would only be cost-effective
if the five-year risk of breast cancer is very high (more than 5
percent). For women age 51-59 years, tamoxifen treatment decisions
need to be individualized according to actual age, whether or not
a woman has had a hysterectomy, and whether their five-year risk
of breast cancer is at least 3.5-4 percent.
Tamoxifen is not appropriate for women with a high risk of cerebral
vascular disease (such as known atherosclerosis or strong family
history of stroke) or a hypercoagulable state.
Physicians can quickly calculate a woman's five-year risk of breast
cancer by using the Gail Model, a formula that incorporates current
age, age at menarche, age at birth of first child, race, breast
biopsy history, and family history of breast cancer. The electronic
version of The Gail Model is available through the National Cancer
Institute at http://cancer.gov/bcrisktool.
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