Health at diagnosis may drive breast cancer survival gap

Differences in the health and tumor characteristics of white and black women with breast cancer at the time of their diagnoses may be largely to blame for the disparity in survival between the two groups, a new study suggests.

Disparities in treatment quality are not the main problem, the researchers conclude, after finding that if differences in the women's overall health and the degree to which the cancer had advanced at the time of diagnosis were eliminated, the survival gap would shrink dramatically.

"The remarkable thing we found is that three-year disparity went down to about one year," said Dr. Jeffrey H. Silber, the study's lead author and the Nancy Abramson Wolfson Endowed Chair in Health Services Research at The Children's Hospital of Philadelphia.

Currently, the U.S. National Institutes of Health estimates that about 12 percent of women will be diagnosed with breast cancer and about 89 percent of them can be expected to be alive five years later.

Previous studies, however, have found large differences in the five-year survival rates of black and white women diagnosed with breast cancer.

In an attempt to find a cause for that gap, Silber and his colleagues used a new statistical model to compare one group of 7,375 black women with breast cancer to three separate groups that each included 7,375 white women with breast cancer.

All the women were in Medicare, the U.S. government-run health insurance for the elderly and disabled, and all were over 65 years old when they were diagnosed between 1991 and 2005.

The researchers found the five-year survival for black women with breast cancer was about 56 percent. That compared to about 69 percent for white women with breast cancer who were matched to the black women by age and year of diagnosis.

That overall difference between racial groups remained virtually unchanged during the 15-year period analyzed.

But when the researchers compared the black women to a group of white women matched for general health and tumor characteristics at time of diagnosis, the survival gap shrank from 12.9 percentage points to 4.4 percentage points.

And within that comparison, when the researchers also matched the women for the treatment they got, the gap further shrank by less than one percentage point.

Based on the findings, Silver told Reuters Health that focusing on ways to improve black women's overall health and the characteristics of their tumors at the time of their diagnoses would do more to reduce the gap in survival rates, compared to improvements in treatment.

"It appears that the presentation is far more important than the disparity in treatment," he said.

Dr. Jeanne Mandelblatt, who co-wrote an editorial accompanying the new study in the Journal of the American Medical Association, said the report has several limitations that may underestimate the effect of improving treatment in black women.