The study reviewed here found that women with higher incomes and women who live in urban areas have had larger drops in breast cancer rates compared to women with lower incomes and women who live in suburban or rural areas. It's not clear what's causing the difference.
Since 2002, there's been a large decrease in breast cancer diagnosis rates. A dramatic change in the use of hormone replacement therapy (HRT) contributed to the decline. Women take HRT to manage bothersome menopausal symptoms, such as hot flashes, night sweats, and insomnia. Research released in 2002 showed that using HRT significantly increases breast cancer risk while HRT is taken and for some time after HRT is stopped. These results led to a large drop in HRT use. Doctors are now much less likely to prescribe HRT to manage menopausal symptoms. Women already using HRT, or who are considering HRT, are now urged to use HRT for the shortest time possible and to consider using estrogen-only HRT. Other research has shown that breast cancer risk linked to HRT use can be minimized by taking HRT for a short period of time and by using estrogen-only HRT (instead of combination HRT, which contains both estrogen and progesterone).
In this study, the researchers looked at the records of more than 475,000 non-Hispanic white women, 50 to 74 years of age, diagnosed with invasive or non-invasive breast cancer between 1997 and 2004. The researchers noted the women's household income and where they lived -- rural, suburban, or urban areas.
The results:
The study didn't say why these differences happened. One possible reason might be that before 2002 urban women and women with higher incomes were more likely to use HRT. If so, then when HRT use started to decline in 2002 the resulting decrease in breast cancer diagnoses would be greatest in these same groups.
It's very clear, though, that HRT increases breast cancer risk, no matter where a woman lives or how much money she earns. Still, menopausal side effects can dramatically reduce quality of life for some women. These women have to weigh the benefits of HRT against the risks.
If you're having severe hot flashes or other menopausal side effects and are considering HRT, talk to your doctor about all of your options. Ask your doctor how you can minimize your breast cancer risk AND relieve your symptoms. Be sure to discuss the pros and cons of different types of approved HRT. Research suggests that estrogen-only HRT appears to increase breast cancer risk less than combination HRT. If you do decide to take HRT, ask if you can take a lower-dose formula and try to take it for the shortest time possible. Learn more about menopause and ways to manage side effects in the Breastcancer.org Managing Menopausal Symptoms section.
CLEVELAND, June 26 (MedPage Today) -- The nationwide drop in breast cancer rates linked to the decline of hormone replacement therapy tracks both income and locale, with more significant reductions observed in affluent, urban areas, a new study shows.
From 2001 to 2004 the overall incidence of invasive breast cancer fell by 13.8% in urban areas, versus a 7.5% decline in rural areas, according to Amelia K. Hausauer, PhD, of the Northern California Cancer Center in Fremont, and colleagues.
Likewise, invasive breast cancer rates fell by 13% in neighborhoods in high-income counties, compared to a 9.6% decline in poor counties, although the intracounty changes from baseline were significant in each case (P<0.001), the group reported in the open access journal BMC Medicine.
"Breast cancer incidence trends for rural counties, which peaked in 1999 and then declined steadily, differed from those in observed in urban counties, where rates fell most dramatically after 2002," they remarked.
This distinctly different pattern of decline is "consistent with the changing pattern of [hormone therapy] prevalence and cessation or noninitiation," the authors concluded.
The use of hormone replacement increased steadily until 1999, when it peaked at 92 million prescriptions. It remained steady until the watershed moment of July 9, 2002.
On that day, the National Health Lung and Blood Institute announced that it had pulled the plug on a study investigating health claims for hormone replacement (estrogen-progestin) in 14,749 healthy women, when it discovered that the five-year incidence of breast cancer was significantly higher among women assigned to hormone therapy compared with those taking placebo.
Following that announcement, there was a significant decline in the use of hormone therapy, and in the past year a number of studies have reported a subsequent decline in breast cancer incidence.
Dr. Hausauer and colleagues analyzed data from 29 population-based cancer registries that participate in the North American Association of Central Cancer Registries.
According to the registry, there were 475,523 cases of invasive breast cancer and 111,885 cases of in situ breast cancer diagnosed between from 1997 through 2004.
The researchers limited their analysis to cases reported in non-Hispanic white women age 50 to 74, and stratified the findings by counties of residence at the time of diagnosis. The counties were further stratified by rural/urban status and by income.
Among the findings:
Although hormone therapy seems a likely explanation for the declines seen in this analysis, the authors cautioned that some of the change -- especially the slow but steady decline observed in rural communities -- could be explained by "saturation of or decreases in mammographic screening."
The authors said their report was limited by the lack of individual socioeconomic information, and a lack of adjustment for possible delays in reporting. Moreover, the authors could not stratify the results by gene-expression subtype or by hormone receptor status.
Dr. Hausauer declared that she had no competing interests.
The registries used in the study were supported by individual states with additional funding from the CDC, and, in some cases, the National Cancer Institute's SEER Program.
Primary source: BMC Medicine Source reference: Hausauer AK, et al "Recent trends in breast cancer incidence in US white women by county-level urban/rural and poverty status" BMC Med 2009.
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