Debrah Reid, who has breast cancer, at home in Memphis, where mortality risk is greater for blacks. Credit Ruth Fremson/The New York Times

A troubling racial divide in breast cancer mortality continues to widen in most major cities around the country, suggesting that advances in diagnosis and treatment continue to bypass African-American women, according to new research.

An analysis of breast cancer mortality trends in 41 of the largest cities in the United States shows that the chance of surviving breast cancer correlates strongly with the color of a woman’s skin. Black women with breast cancer — whether they hail from Phoenix or Denver, Boston or Wichita, Kan. — are on average about 40 percent more likely to die of the disease than white women with breast cancer.

In some cities, the risk is even greater. In Los Angeles, a black woman with breast cancer is about 70 percent more likely to die from the disease than a white woman is. In Memphis, black women face more than double the risk, according to the research, published on Tuesday in Cancer Epidemiology.

The findings were compiled and analyzed by the Sinai Urban Health Institute in Chicago and the Avon Foundation for Women, which also funded the research. The analysis builds on a series of studies that have identified a startling racial gap in breast cancer mortality.

In 2012, a widely publicized study of the 24 largest cities examined the racial gap in breast cancer from 2005 through 2007. The new study takes a longer view and includes breast cancer deaths from 1990 through 2009 in 41 cities.

The more comprehensive analysis shows that in most cities 20 years ago, black and white women faced about the same mortality risk from breast cancer. But starting in 1990, the death rate among white women began to drop rapidly in many cities while death rates among black women fell only a little.

“It’s absolutely startling and very dismal, because there is hardly any health measure in the United States that hasn’t improved in the last 20 years,” said Steve Whitman, director of Sinai Urban Health Institute and the study’s senior author.

Notably, death rates for black and white women with breast cancer declined over all during the two-decade study period; however, the death rates among white women decreased twice as much as those among black women.

The researchers said the difference is explained by lower access to screening, lower-quality screening, less access to treatment and lower-quality treatment among black women.

Dr. Whitman said the larger question is why the health system appears to discriminate against black women with breast cancer.

“It’s undeniable that this is systemic racism,” he said. “I don’t mean that a bad person is at the door personally keeping women out, but the system is arranged in such a way that it’s allowing white women access to the important gains we’ve made since 1990 in terms of breast health, and black women have not been able to gain access to these advances.”

The research also dispels the notion that black women face a higher risk of breast cancer because of genetic differences. While they are at greater risk for some types of breast cancers, that doesn’t explain the widening mortality gap developing in a relatively short period of just two decades.

“Mathematically, it can’t be anything genetic,” Dr. Whitman said. “How could genes change in 20 years?”

The next step is to begin to study differences in the racial gap across cities in hopes of identifying the factors that contribute to the problem. The cities with the largest disparities are Memphis, Los Angeles, Wichita, Houston, Boston, Denver, Chicago, Phoenix, Dallas and Indianapolis.

In New York, the gap is far smaller. While black women are still 19 percent more likely to die of breast cancer than white women, over all both white and black women with breast cancer fare better in New York than in many other cities.

“New York is the largest city in the country, yet it only has a nominal disparity compared to Los Angeles or Chicago or Houston,” said Marc Hurlbert, executive director of the Avon Breast Cancer Crusade and one of the study authors. “No disparity is acceptable, but New York is doing something better than other cities.”

Dr. Hurlbert said factors like the city’s public hospital system and an extensive public transportation system probably play a role, increasing access to breast cancer care regardless of income level. However, more research is needed to home in on the factors that are contributing to the racial divide.

“Can we help cities with a wide gap learn from the cities that are doing better?” Dr. Hurlbert said. “Now that we have the data and understand what is going on, we’re going to move to trying to solve the problem.“

Written by Tara Parker-Pope for the New York Times, March 3, 2014.

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