They used data from Medicare and the National Cancer Institute's Surveillance Epidemiology and End Results (SEER). They compared information from 7,375 black patients over age 65 with three groups of the same size composed of white women. One was matched for demographics, another for demographics and initial health characteristics or presentation, and the third for demographics, presentation, and treatment.
There were some treatment differences: Blacks waited longer between diagnosis and treatment, were sometimes treated with a different mix of medications, and were less likely to receive other treatment after breast-conserving surgery. Still, the research team concluded that those differences accounted for less than a percentage point of the survival difference.
What explained most of the difference in survival was that the black women already had more problems when they were diagnosed with cancer. They were more likely to have other serious health problems such as heart failure or diabetes. Black patients were more likely to come in with larger tumors and more advanced cancer.
The researchers said their analysis supported the idea that the black women had received "less adequate primary care" than demographically similar white women.
They said breast-cancer care is more effective for women who are diagnosed earlier. "It may be difficult to eliminate the racial disparity in survival from diagnosis unless differences in presentation can be reduced," they said.
An editorial by experts at Georgetown and Columbia Universities that accompanied the research article pointed out that racial disparities in survival did not emerge until the late 1980s, when mammograms and effective treatments in addition to surgery became available.
The editorial writers said the data that the Children's and Penn team used were not detailed enough to measure the quality of treatment the women received.
They said the "rigorous" study provided more "clues" about why racial differences have persisted, largely unchanged, since 1991. "Ultimately, for any cancer control strategy to succeed," they wrote, "improved care quality appears to be a necessary, but not sufficient, condition to eliminate race- based mortality differences in the United States."
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