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The number of breast cancer cases in the United States appears to be declining, according to the results of a newly
published study. Researchers found that between 2002 and 2003, 7% fewer women were diagnosed with breast cancer. The
sharpest decline was found among women between the ages of 50 and 69; 12% fewer women in this age group were
diagnosed with breast cancer. Researchers believe that the decreased use
of hormone replacement therapy (HRT) could be behind the decline in diagnoses.
"It is the largest single drop in breast cancer incidence within a single year I am aware of," says
Peter Ravdin, M.D., Ph.D., a research professor in the Department of Biostatistics at M. D. Anderson, in the Center's news release.
Prior to July 2002, breast cancer cases have increased over the past 20 years. Researchers had attributed
part of this trend to the increase in the use of screening mammography. Breast cancers were being diagnosed in
earlier stages, which also increased chances of survival. However, researchers had thought that
the increased use of HRT among menopausal and post-menopausal women might be a factor in the rise of breast cancer diagnoses.
HRT is synthetic estrogen and/or progesterone (progestin) designed to "replace" a woman's depleting
hormone levels. Decreased levels of estrogen during menopause may cause hot flashes, vaginal dryness,
sleep disturbances, or other bothersome side effects. The dryness of tissue surrounding the vagina
and urethra may cause pain during sexual intercourse or urination, and HRT helps to
relieve these and other menopausal symptoms.
While HRT has been shown to be effective at relieving menopausal symptoms and may provide protection
against conditions such as osteoporosis, recent research has shown that HRT may increase the risk of breast cancer. In
July 2002, the National Institutes of Health halted a large study on HRT, called the Women's Health
Initiative, because the combined estrogen/progestin regimen of the therapy was found to cause 8
cases of invasive breast cancer for every 10,000 women on HRT (a 26 percent increase in breast cancer
risk compared to women who do not take HRT).
In the current study, Donald Berry, Ph.D. of the M.D. Anderson Cancer Center and colleagues studied breast cancer diagnoses in
nine areas of the United States that contribute data to the National Cancer Institute's Surveillance Epidemiology and
End Results (SEER) database. They found that while breast cancer cases increased by 1.7% per year from
1990 to 1998, and when age was taken into account, diagnoses remained generally stable between 1998 and 2002.
However, between 2002 and 2003, there was a 7% decrease in the number of breast cancer cases diagnosed. This amounts
to 14,000 fewer cases of breast cancer.
When the researchers looked closely at the 2003 data, they found a decrease among certain types of breast
cancers that are dependent upon estrogen (called estrogen-receptor positive breast cancers). There was an 8%
decline in these types of breast cancers in 2003, and a 12% decline among women aged 50 to 69, as
compared to 4% decline in breast cancers that were not estrogen dependent.
Researchers cannot definitely say whether the reduction in HRT use is the underlying cause in the decline in breast
cancer cases. However, according to the researchers, about 30% of women older than 50 had been taking HRT
in the early 2000s but that about half of these women stopped using HRT in late 2002 after the Women's
Health Initiative study was halted.
"Research has shown that estrogen receptor-positive tumors will stop growing if they are deprived of the
hormones, so it is possible that a significant decrease in breast cancer can be seen if so many
women stopped using HRT," said Ravdin in an M.D. Anderson news release.
This information can be confusing for menopausal and post-meonpausal women who have been bombarded with
conflicting messages about the safety of HRT. Women at high risk of breast cancer (as determined
by family and personal history, etc.) may be advised not to take HRT, but for women at low risk
of the disease, the benefits of short-term HRT use could outweigh the possible risks. At the moment, the best
advice experts can give is for women to discuss the benefits and
risks of HRT with their physicians and make informed choices.
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