TUESDAY, April 15 (HealthDay News) -- Although the overall
incidence of breast cancer dropped dramatically after millions of
American women stopped using hormone-replacement therapy in 2002,
that decline doesn't seem to have benefited black women.
In fact, the rates of invasive breast cancer stayed essentially
the same for black women from 2002 through 2004, while they were
sharply decreasing for whites and Hispanics, according to a study
presented April 13 at the American Association for Cancer Research
annual meeting, in San Diego.
"In women in the age group from 50 to 69 -- those more likely to
use hormone-replacement therapy -- we found that the reduction in
invasive breast cancer with estrogen-receptor positive tumors was
like 13 percent for whites, 11 percent for Hispanics, about 4
percent for Asian or Pacific Islanders and no change for
African-Americans," said the study's lead author, Dezheng Huo, an
epidemiologist at the University of Chicago Medical Center.
Huo said several factors could be at play. One is that mammogram
screening programs might not be effectively reaching all racial
groups. Another factor is that black women have less
estrogen-receptor positive cancers, and so the decline in HRT use
might not have as dramatic an effect on their cancers, he
speculated.
Another reason might be that black women may have used HRT less
frequently than white women, and so again wouldn't be as affected
by the declining use of hormones. Elizabeth Ward, director of
surveillance research for the American Cancer Society, said that at
least one past study found baseline use of HRT of about 14 percent
of women prior to 2002, compared to only about 10 percent of black
women.
When research results from mid-2002 suggested that taking HRT
might increase a woman's risk of heart disease and cancer, many
women stopped taking these supplements. Almost immediately after
women aged 50 to 69 stopped taking HRT, the rates of
estrogen-receptor-positive breast cancer began to decline sharply
in whites, about 2 percent for every three months during the second
half of 2002 and all of 2003, according to Huo. The decline
stabilized in 2004. During that same time frame, there was no
change for black women. Estrogen-receptor-positive breast cancers
are fueled by the female hormone estrogen.
Huo and his colleagues gathered the study data from 17 cancer
registries, covering about 26 percent of the U.S. population.
The researchers also looked at the effect of declining HRT use
on estrogen-receptor-negative tumors, and found a slight reduction
for whites and Hispanics, but a slight increase in black women.
According to the researchers, about 80 percent of tumors in white
women are estrogen-receptor-positive, compared to about 60 percent
in black women. Women from Nigeria, for example, have
estrogen-receptor-positive tumors only about 30 percent of the
time, according to the researchers.
Ward said it's important to realize that the differences in
tumor types might not be due to race, but due to environmental and
social factors.
Huo's team also examined the effect of stopping HRT on very
early breast cancers, and found virtually no change.
At the end of 2004, there was a slight increase in the rates of
invasive breast cancer for Asian/Pacific Islanders, which Huo said
might be attributable to an increased rate of mammography in this
group of women.
"This is an area of a great deal of interest -- we've known that
black women have a lower incidence of breast cancer, but higher
mortality rates. No one really understands why," said Ward, who
added that all women should get a mammogram every year.
"Mammography can detect breast cancer early and can decrease the
risk of dying early," she said.
More information
To learn more about what's known about race and breast cancer,
visit the
American Society of Clinical Oncology.
