Research struggles to understand why black and white women are affected differently
By Dennis Thompson
(HealthDay News) -- Breast cancer occurs more often in white women than in black women in the United States, but it kills more black women than white.
This is known as the "racial gap" of breast cancer, a provocative topic for cancer researchers hoping to save lives.
Several studies released in the past year have tried to figure out why breast cancer is more fatal to black women. One factor that's been addressed is the fact that black women are more likely to contract a specific form of breast cancer, known as triple-negative breast cancer, that is much more difficult to treat.
"There is a higher proportion of black women with triple-negative disease -- 30 percent versus 18 percent of whites," said Dr. Otis W. Brawley, chief medical officer of the American Cancer Society and a professor of hematology, oncology and epidemiology at Emory University in Atlanta.
Triple-negative breast cancers do not respond to the best biologic treatments available, reducing the treatment options available to doctors.
"We don't have a lot of options for these women other than chemotherapy, and their cancers tend to be more aggressive," said Dr. Christy Russell, an oncologist and chief of medicine at the University of Southern California/Norris Cancer Hospital and chairwoman of the Breast Cancer Advisory Committee at the American Cancer Society.
However, black women's lack of access to health care and breast cancer screenings is also believed to make a significant contribution to the racial gap.
"The number one theory is that black women are more likely to be in a lower socioeconomic status and are more likely to be diagnosed late," Russell said. "Not only do they not get screened, but when they are diagnosed with cancer, their entry into medical treatment is delayed."
National Breast Cancer Awareness Month occurs in October, and issues such as the racial gap will be part of the discussion as medical experts spread the word about this disease.
An estimated 192,370 new cases of breast cancer are expected to be diagnosed in 2009, according to the American Cancer Society. Breast cancer will kill an estimated 40,610 people this year.
The racial gap behind those figures has been well-documented. Between 2000 and 2004, 132.5 of every 100,000 white women in the United States were diagnosed with breast cancer, compared with 118.3 of every 100,000 black women, according to the Cancer Society.
But during the same time period, breast cancer killed 33.8 of every 100,000 black women, compared with 25 of every 100,000 white women.
A pair of studies published July 15 in the Journal of the National Cancer Institute attempted to tackle the racial gap but came up with conflicting answers.
One study by researchers at the U.S. National Cancer Institute found that if you control for the incidence of triple-negative breast cancer, which has proven resistant to the best biologic treatments available, the racial gap remains largely in place. They concluded that either poor access to health care or some other unknown biological cause is to blame for the gap.
But another study, this one led by researchers at Loyola University near Chicago, cast doubt on the notion that poverty and poor access to health care cause lower cancer survival rates. Evaluating nearly 20,000 adults with cancer who received identical treatment and access to care in clinical trials from late 1974 through late 2001, the researchers found that blacks were 21 to 61 percent more likely to die from gender-specific cancers than whites.
Some medical experts believe that a combination of the two potential causes is the most likely explanation for the racial gap, barring some unforeseen cause that has not been discovered.
Brawley and Russell note that nearly all U.S. studies to date have found that black and white women who receive similar care for similar cancers have similar survival rates.
"If they are found at the same time and treated the same and their cancers have similar features, all of the data suggest their outcomes will be the same," Russell said.
In fact, Brawley noted that one segment of the female black population has breast cancer death rates that are more similar to those of white women: black women who are in the Department of Defense health system.
"These women are in the system because they or their husband did 20 or more years in the military," Brawley said. "They had the same preventive care over an adult lifetime and the same quality of health care. They have very similar mortality compared to whites, much closer to white death rates than to black American rates," he added.
"They lose 70 percent of the disparity," Brawley continued. "That suggests that access to care and quality of care, which is worse for black Americans, determines the majority of the black-white disparity."
He noted that one theory links the increased incidence of triple-negative breast cancer in black women with lower socioeconomic status.
Researchers in Scotland found that poor women who are white tend to be diagnosed with triple-negative breast cancer at a younger age, and they have linked that type of cancer to a higher body mass index (BMI, an indicator of body fatness calculated from a person's weight and height) in poorer women, Brawley said.
"In the U.S., black women have a BMI disparity compared to whites," he said. "A much higher proportion of black women are obese. Poverty and obesity likely account for a large part of the black-white pathology difference and worse quality of care, which, again, worsens the disparities in mortality."
On the Web
The U.S. National Cancer Institute has more on breast cancer.
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