In the largest cities in the U.S., death rates from breast cancer have dropped across the board over 20 years, but far less so for black women than whites, according to a new analysis.
The widening survival gap is likely due to differences in the quality of healthcare and access to it, researchers contend, because health factors alone cannot explain the changes over two decades.
"The advancements in screening tools and treatment which occurred in the 1990's were largely available to White women, while Black women, who were more likely to be uninsured, did not gain equal access to these life-saving technologies," lead author Bijou Hunt, an epidemiologist at Mount Sinai Hospital in Chicago, told Reuters Health in an email.
Past research has examined racial differences in survival for specific cancers and for cancer in general and found at least some could be explained by biology. High blood pressure, diabetes and other health problems that both worsen cancer outcomes and are more common among blacks have received some of the blame.
Black women are also more likely than whites to have aggressive breast tumors that don't respond to the most effective treatments. This basic difference in cancer genetics is another reason given for differing survival when it comes to breast cancer.
To assess changes in survival trends on a national level, Hunt and her colleagues looked at mortality rates in the largest U.S. cities at four different time points: 1990-1994, 1995-1999, 2000-2004 and 2005-2009.
They found that during the 20-year span, deaths from breast cancer fell overall - by 13 percent for black women and by 27 percent for white women. While a gap was already present in the early 1990s, it widened considerably with time.
The team's analysis, published in the journal Cancer Epidemiology, found that during 1990-1994, the rate of breast cancer deaths was 17 percent greater among blacks than among whites. This steadily increased to 30 percent, then to 35 percent and finally to 40 percent in the last time period they looked at.
The disparity was particularly striking in Memphis, Tennessee, where the rate of breast cancer deaths among blacks was 27 percent higher than among whites in 1990-1994 and ballooned to more than two-fold higher by 2005-2009.
In Los Angeles, the mortality rate among blacks was 24 percent higher than among whites in 1990-1994 and 71 percent higher in 2005-2009.
Wichita, Kansas, which had no significant differences in mortality rates among blacks and whites at the first time point studied, had a two-fold increased rate of deaths among blacks in 1995-1999, which fell to a 57 percent greater mortality rate among blacks by the most recent time point.
Most, but not all, of the 41 cities included in the final analysis saw an increase in racial disparities during the study period. This was not true of New York, however, the largest city included. The disparity in New York was about the same at the first and last time points examined, with an 18 to 19 percent greater mortality rate among blacks than whites, the researchers note.
Several other large cities, including Minneapolis, Miami, Portland and Las Vegas, did not have any significant differences at all in mortality rates between blacks and whites at any of the four time periods examined.
The growing gap in breast cancer deaths among blacks versus whites was largely caused by a steeper drop in breast cancer deaths among whites than among their black counterparts, Hunt and her colleagues point out.
Sixteen states experienced a greater than 20 percent decrease in the white mortality rate, but a less than 10 percent decrease in mortality among blacks, the researchers report.
"If genetics were responsible . . . we would not have seen the rates go from being nearly equal in most places at the first time point to being so much worse for Black women than for White women at the last time point," Hunt told Reuters Health.
Increased screening and treatment options among whites, coupled with both a lack of access to and lower quality of screening and treatment among blacks appear to be the more important culprits, she and her coauthors speculate in their report.
Dr. Otis W. Brawley, chief medical officer for the American Cancer Society, agrees with this assessment. He told Reuters Health that he gets "frustrated" when experts focus on biological differences between blacks and whites - "issues that we can't fix" - instead of logistical issues such as increasing access to care.
Brawley, a medical oncologist and epidemiologist at Emory University in Atlanta, Georgia, was not involved in the current study.
The "power" of Hunt's study, Brawley said, is the authors' ability to show different mortality curves for different cities.
"Black people in New York are not genetically different from black people in Chicago, but their outcomes are different," he said.
In Chicago, the study found, mortality rates were initially insignificant between blacks and whites in 1990-1994, but were 48 percent greater among blacks by 2005-2009.
"Most of the disparities are actually due to access to care and access to quality care," Brawley said. "This is an ethical and moral problem that we in the United States have yet to come to grips with."
Brawley added that a "pet peeve" of his is that much attention is given to screening and early diagnosis, but there is a lack of focus on increasing access to care and quality care.
"This is not new science, this is getting old science to people who deserve it because they are human beings," he said. "That is where we as a society are failing."
Individuals also have a role to play in ensuring they get proper care, he added. "Once one has insurance and has access to care, one needs to be focused and involved in one's care," Brawley said, such as asking questions and learning about the disease.
Breast cancer is the second-leading cause of cancer death among U.S. women, after lung cancer. It is diagnosed in close to 1.3 million people around the world every year and kills 500,000.