Difference in Breast Cancer Survival Between Black and White Women Has Not Changed Substantially
In an analysis of 5-year survival rates among black and white women diagnosed with breast cancer between 1991 and 2005, black women continued to have a lower rate of survival, with most of the difference related to factors including poorer health of black patients at diagnosis and more advanced disease, rather than treatment differences, according to a study published online today in JAMA.
Health-care investigators have been aware of the racial disparities in survival among women with breast cancer for the past 20 years. Numerous studies have documented worse treatment outcomes in black patients with breast cancer than white patients, and have identified potential reasons for the disparities, including differences in screening, presentation, comorbid conditions on presentation, tumor biology, stage, treatment, and socioeconomic status.
Study Details
Jeffrey H. Silber, MD, PhD, of the Children’s Hospital of Philadelphia, and colleagues examined the extent of the racial differences in breast cancer survival in the Medicare population and the reasons the disparity exists. The study compared 7,375 black women 65 years and older diagnosed between 1991 to 2005 and three sets of 7,375 matched white control patients selected from 99,898 white potential control patients, using data from 16 U.S. Surveillance, Epidemiology and End Results (SEER) sites in the SEER-Medicare database. All patients received follow-up through December 2009.
The black case patients were matched to three white control populations on demographics (age, year of diagnosis, and SEER site), presentation (demographics variables plus patient comorbid conditions and tumor characteristics such as stage, size, grade, and estrogen receptor status), and treatment (presentation variables plus details of surgery, radiation therapy, and chemotherapy).
Results
The researchers found that the absolute difference in 5-year survival (55.9% in black patients vs 68.8% in white patients) was 12.9% in the demographics match. This difference remained unchanged between 1991 and 2005. After matching on presentation characteristics, the absolute difference in 5-year survival was 4.4% and was 3.6% lower for black patients than for white patients matched also on treatment.
Regarding differences in treatment by race, overall, 12.6% of black patients did not have evidence of receiving any treatment for their breast cancer, compared with 5.9% of whites. Average time from diagnosis to treatment was longer among blacks than among demographics-matched whites (29.2 vs 22.5 days). Black women were also more likely to have long delays in treatment: 5.8% of black patients did not initiate treatment within the first 3 months from diagnosis, compared to 2.5% of white patients.
Black women also received breast-conserving surgery without any other treatment more often than presentation-matched whites (8.2% vs 7.3%). “Nevertheless, differences in survival associated with treatment differences accounted for only 0.81% of the 12.9% survival difference,” the authors wrote.
There were large differences in the way black and white patients presented. “For the demographics match, blacks had significantly less evidence of at least one primary care visit than matched whites (80.5% vs 88.5%, respectively); significantly lower rates of breast cancer screening (23.5% vs 35.7%); and significantly lower rates of colon cancer and cholesterol screening,” the authors noted.
Eliminating Racial Disparity Is a Difficult Task
“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 authors 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. The disparity in treatment might matter more if the disparity in presentation were reduced, because blacks would then be diagnosed with less advanced disease, for which treatment is more effective.”
The researchers add that black patients are diagnosed not only with more advanced breast cancers but also with more unrelated comorbid conditions. “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,” they concluded.
This research was funded through a grant from the Agency for Healthcare Research and Quality, Department of Health and Human Services, and by the U.S. National Science Foundation. The study authors reported no potential conflicts of interest.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.