Health News
2006-10-21
Hormones now
linked to breast cancer's ethnic gaps
Differences in
estrogen levels may partially explain the ethnic
disparities in breast cancer rates among U.S. women, new
Differences in
estrogen levels may partially explain the ethnic
disparities in breast cancer rates among U.S. women, new
research suggests.
In a study of
more than 700 postmenopausal women, researchers found that
participants' blood levels of estrogen and "male" hormones,
called androgens, varied by race and ethnicity. And the
differences in estrogen, which fuels breast tumor
growth, often paralleled ethnic differences in breast
cancer risk.
Native Hawaiians,
for example, had the highest levels of estrogen and
androgen, and the highest rate of breast cancer. On average,
their estrogen levels were about one quarter higher
than those of white women, according to findings
published in the journal Cancer Epidemiology, Biomarkers
& Prevention.
Similarly, the
study found, women of Japanese descent had higher estrogen
levels than white women did, and their breast cancer rate
followed suit.
These findings
fit the theory that racial or ethnic differences in
estrogen levels account for some of the differences seen in
breast cancer rates, according to study leader Dr.
Veronica Wendy Setiawan of the University of Southern
California in Los Angeles.
An exception, she
told Reuters Health, was the finding that
African-American women had lower rates of breast cancer than
white women did, despite having higher estrogen levels.
"We can't explain
that yet," Setiawan said. It's known that before
menopause, black women have a higher risk of breast cancer
than white women, she noted. So it's a puzzle as to
why their risk doesn't remain elevated after
menopause, even though their estrogen levels remain
relatively high.
Another finding
with no clear explanation is that Japanese American women
had higher estrogen levels and a higher rate of breast
cancer than white women did—a stark reversal of
what's been previously observed.
This rise in
estrogen levels among Japanese Americans may be driving the
rise in breast cancer, according to Setiawan, but no one
knows what factors—such as diet or other
lifestyle changes—are affecting estrogen levels
in these women.
Excess body fat
raises estrogen levels, but Japanese Americans in the
study were generally thinner than other women.
The findings are
based on 739 women who are part of a larger study that
has followed an ethnically diverse group of adults from
California and Hawaii for more than a decade.
Setiawan notes
that more research is needed to figure out why black women
differ from other women when it comes to the relationship
between estrogen levels and breast cancer—and
why estrogen levels appear to be changing among
Japanese women. (Reuters)
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