Number of Breast Cancer Cases Continue to Decline (dateline May 16, 2007)
New research reveals that breast cancer cases declined by over 8% from 2001 through 2004. The results of this research complement a U.S. government study published in December 2006 that found that 7% fewer women were diagnosed with breast cancer between 2002 and 2003. The researchers of that study believed that the decline in breast cancer could be the result of fewer women choosing to use hormone replacement therapy (HRT). The new research reveals that the decline in cases occurred among women over age 50, the most likely candidate for HRT.
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 December 2006 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.
Peter Ravdin, M.D., Ph.D., a research professor in the Department of Biostatistics at M. D. Anderson called the results of the December 2006 study "the largest single drop in breast cancer incidence within a single year I am aware of," says, in an M.D. Andersen news release.
To conduct the current study, Ravdin and his colleagues again examined medical information from the National Cancer Institute's SEER database. They found a decrease in breast cancer cases of 8.6% from 2001 through 2004. The decrease occurred only in women who were 50 years of age or older and occurred more in women whose cancers were estrogen-receptor positive. These types of cancer depend on the hormone estrogen.
Researchers cannot definitely say whether the reduction in HRT use is the underlying cause in the decline in breast cancer cases. However, they believe it is likely that the decrease in hormone use after the results of the 2002 Women's Health Initiative were published contributed to the decline. Other factors could include the decline in screening mammography among women aged 50 and older. As stated earlier, screening mammography has been shown to increase breast cancer rates because the exam has the ability to detect small cancers that previously went undetected.
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.