The racial disparity in breast cancer survivability persists a generation after researchers first observed higher death rates among African American women.

In America, black women are more likely to die of breast cancer with a 55.9-percent survivability rate compared to 68.8 percent for white women, researchers at Children's Hospital in Philadelphia found in a recent study.

Following improvements to breast cancer screening and treatment, black women diagnosed between 1991 and 2005 continued to die at higher rates over a five-year period, with most of the discrepancy blamed on generally poorer health and more advanced disease, rather than any differences in treatment.

"For 20 years health care investigators in the United States have been keenly aware of racial disparities in survival among women with breast cancer," the researchers wrote Wednesday in the Journal of the American Medical Association. "Numerous reports have not only identified and documented worse outcomes in black patients with breast cancer but have suggested potential reasons for the disparities based on differences in screening, presentation, comorbid conditions on presentation, tumor biology, stage, treatment, and socioeconomic status."

In looking at Medicare patients, Dr. Jeffrey H. Silber sought to pinpoint the reason for the disparity by comparing 7,375 elderly black women with three sets of exactly the same number of elderly white women, all diagnosed with breast cancer during the five-year period. The white study participants were selected from a pool of nearly 100,000 patients, culling data from 16 different Medicare databases in the U.S. Surveillance, Epidemiology and End Results (SEER) collection of repositories.

An Unexplained Gap: 3.6 Percent

To isolate any possible explanation for the racial disparity, Silber and his colleagues matched black Medicare patients to white women of similar age who were diagnosed in the same year while living in roughly the same geographic area, as shown by enrollment in SEER databases. The researchers also matched patients with similar health profiles, including demographic variables and co-occurring disease conditions, as well as the stage, size, grade, and estrogen-receptor status of breast cancer tumors.

Still, the racial gap persists. When matching patients head to head, researchers found that disease management accounted for a bit of the 4.4-percent absolute difference between white and black women, with an unexplained difference of 3.6 percent.

Overall, more black women in the study population did not receive treatment for breast cancer, at 12.6 percent compared to 5.9 percent for whites. But there was also a longer gap for black women from diagnosis to treatment when compared to whites with similar demographics. After diagnosis, a black woman typically went 29.2 days until beginning treatment, compared to 22.5 days for their white counterparts.

Delays in treatment outside of the typical experience were also more pronounced among black women, with 5.8 percent initiating treatment within a three-month period following diagnosis, compared to 2.5 percent of white patients.

African American women were slightly more likely than white counterparts to receive breast-conserving surgery, a less radical form of mastectomy that removes only part of the breast, as the sole form of treatment.

"Nevertheless, differences in survival associated with treatment differences accounted for only 0.81 percent of the 12.9 percent survival difference," the researchers wrote.

Differences In Health Care

Dramatic points of data jumped from the databases in the way black and white patients "presented" to the health care system at the time of diagnosis.

"For the demographic match, blacks had significantly less evidence of at least one primary care visit than matched whites — 80.5 percent versus 88.5 percent, respectively," researchers wrote. African American women also had significantly lower rates of breast cancer screening at 23.5 percent versus 35.7 percent, and significantly lower rates of colon cancer and cholesterol screening.

"Our results suggest that it may be difficult to eliminate the racial disparity in survival from diagnosis unless differences in presentation can be reduced," the researchers wrote. "There is also a disparity in treatment, with blacks receiving treatment inferior to that received by whites with similar presentation, but this explains only a small part of the observed difference in survival."

Regarding the still mysterious 3.6 percent racial disparity, researchers speculated that more advanced stages of disease on diagnosis may be to blame, as well as other health problems in the mix.

"Some of the effectiveness of cancer treatment for blacks may be blunted by other health problems. If the differences in comorbid conditions at diagnosis were reduced, it is possible that the differences in cancer treatment would matter more for the differences in survival."

Dr. Jeanne S. Mandelblatt, a public health expert at the Georgetown Lombardi Comprehensive Cancer Center, commented on the study in an accompanying editorial. "The rigorous study by Silber [and his colleagues] provides additional clues to the black-white differences in breast cancer outcomes," she wrote. "Ultimately, for any cancer control strategy to succeed, improved care quality appears to be a necessary, but not sufficient, condition to eliminate race-based mortality differences in the United States."

The research was funded by the U.S. Department of Human Services and by the U.S. National Science Foundation.

Source: Kuehn BM. Breast Cancer Disparities. JAMA. 2013.