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Sept. 30, 2004 — A survey conducted in primary care practices showed that a
small proportion of women are eligible for discussions about use of tamoxifen to
prevent cancer, and of those women, the proportion of breast cancers that would
be prevented is also small, according to an article in the Sept. 27 issue of
The Archives of Internal Medicine, a journal of the American Medical
Association.
Despite the importance of screening mammography and breast
examination in breast cancer control, randomized trials show modest effect of
screening on breast cancer deaths, according to background information in the
article. A national breast cancer prevention trial showed a 49 percent reduction
in breast cancer incidence in high-risk individuals who received tamoxifen.
However, according to the article, the same study also showed that the drug
increased the risk of endometrial (uterus) cancer, pulmonary embolism (sudden
blockage of an artery in the lung), blood clots in the deep veins, and
stroke.
Carmen L. Lewis, M.D., M.P.H., from The University of North
Carolina at Chapel Hill, and colleagues surveyed 605 women aged 40 to 69 years
in ten general internal medicine practices in North Carolina in 2000. The survey
was designed to determine each woman’s breast cancer risk and then to assess
eligibility for chemoprevention (using tamoxifen to prevent breast cancer). The
researchers determined the women’s five-year breast cancer risk based on age,
ethnicity, number of first-degree relatives with breast cancer, age at first
menstruation, age at first live birth, number of breast biopsies, and presence
of atypical hyperplasia (abnormal cells that may be indicative of cancer) in a
biopsy specimen. Women with an estimated five-year breast cancer risk of at
least 1.66 percent were defined as having an increased breast cancer risk. To
determine the possible risks of taking tamoxifen, the women were questioned
about their medical history; specifically, whether their physicians had told
them they had high blood pressure, diabetes mellitus, blood clots in the legs,
or blood clots in the lungs.
The researchers found that among white
women, nine percent in their 40s, 24 percent in their 50s, and 53.4 percent in
their 60s had a five-year estimated breast cancer risk of 1.66 percent or
greater. Among black women, 2.9 percent in their 40s, 7.1 percent in their 50s,
and 13 percent in their 60s had a similar risk. When the possible side effects
of tamoxifen were considered in white women, ten percent or fewer in all age
groups were judged to be potentially appropriate for chemoprevention using
tamoxifen. In women identified as at an increased risk for breast cancer, the
maximum proportion of breast cancers that would be prevented was 6 to 8.3
percent, according to the researchers’ calculations.
The authors write:
“Small numbers of women in primary care practices are eligible for discussions
about chemoprevention; the maximum proportion of breast cancers prevented is
also small. Challenges lie in targeting discussions to the most appropriate
women and in finding new chemoprevention strategies that have less risk of
harms.”
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