Presentation, Not Treatment, Responsible for Racial Disparity in Breast Cancer Survival

Researchers from The Children’s Hospital of Philadelphia and the University of Pennsylvania recently published a study in the Journal of the American Medical Association (JAMA) that shows differences in how breast cancer patients present at diagnosis are more responsible for racial disparities in 5-year survival than treatment disparities. Jeffrey H. Silber, MD, PhD, professor of Pediatrics, Anesthesiology and Critical Care at the University of Pennsylvania Perelman School of Medicine and professor of Health Care Management at The Wharton School, was the paper’s lead author.

A pediatrician and healthcare economist, since 1997 Dr. Silber has directed CHOP’s Center for Outcomes Research. Dr. Silber, who was recently named the first Nancy Abramson Wolfson Endowed Chair in Health Services Research, has published extensively on the use of multivariate matching in healthcare, and has applied this approach to outcomes research in both pediatric and adult medicine and surgery, disparities research, and cancer research.

“For 20 years, health care investigators … have been keenly aware of racial disparities in survival among women with breast cancer,” the study’s authors write. A number of potential reasons for these disparities have been put forth, including differences in screening, comorbid conditions on presentation, stage, treatment, and socioeconomic status. With the current study, the investigators sought to determine whether racial disparity in breast cancer survival was due to the way patients were treated or to their presentation at diagnosis.

The JAMA study made use of data from Medicare and the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) program, which gathers “information on incidence, prevalence and survival from specific geographic areas representing 28 percent of the US population,” according to the SEER website. The researchers compared a cohort of 7,375 black women 65 years and older with three sets of 7,375 matched white control patients — matched on demographics, then demographics and presentation, and finally demographics, presentation, and treatment — selected from a pool of 98,898 potential white patients who had been diagnosed between 1991 and 2005. All of the patients studied received follow-up through December 31, 2009.

Differences in Presentation Between Whites, Blacks Found

Drs. Silber’s team found a difference in 5-year survival, with blacks displaying an absolute survival rate of just 55.9 percent, versus 66.8 percent for whites matched on demographics, an absolute disparity of 12.9 percent. When matched for presentation characteristics, the absolute difference in 5-year survival was 4.4 percent, and 3.6 percent when matched for treatment. Moreover, the difference in survival did not change significantly between 1991 and 2005.

Intriguingly, the researchers also noted a number of differences between how black and white patients presented at diagnosis. Blacks displayed higher rates of comorbidities than whites. For example, 9.6 percent of the black patients had congestive heart failure at diagnosis, versus 5.9 percent of the demographics-matched whites. Likewise, 26 percent of blacks had diabetes versus 15.3 percent of demographics-matched whites at diagnosis.

Differences in cancer stage and size were also seen. For example, 20 percent of blacks had stage III or IV cancer at presentation, while 12 percent of demographics-matched whites were stage III or IV. And only 11.7 percent of whites matched for demographics had tumors with a diameter of 4 or more centimeters, compared to 21.6 percent of blacks.

While the study’s authors acknowledged some of its limitations — such as the inability to perform chart review to confirm diagnosis and treatment factors — the study’s results “suggest that it may be difficult to eliminate the racial disparity in survival from diagnosis unless differences in presentation can be reduced.” And though there was a “disparity in treatment,” that disparity only explains a small portion of the difference in survival between whites and blacks, with treatment differences accounting for only 0.81 percent of the 12.9 percent difference in 5-year survival, the authors note.

Overall, “treatment differences explained only a small portion of the survival difference because white women who presented like black women (i.e., were matched on demographics and presentation) but who received treatment similar to that received by white women fared almost the same as white women who presented like black women and who were treated in the same way as black women,” the study’s authors conclude.

An editorial that accompanied the study noted that what “is notable about this study, compared with most prior research, is the use of rigorous matching methods to eliminate some of the biases that affect observational analyses.” Jeanne S. Mandelblatt, MD, MPH, of Georgetown University’s Lombardi Comprehensive Cancer Center, acted as the editorial’s corresponding author, while Vanessa B. Shephard, PhD, and Alfred I. Neugut, MD, PhD, of Georgetown and Columbia University, respectively, also contributed to the editorial.

“This rigorous study … provides additional clues to the black-white differences in breast cancer outcomes. 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,” said the editorial’s authors.

To read more, see the JAMA study.