In an analysis of five-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.
Most of the difference was related to factors including poorer health of black patients at diagnosis and more advanced disease, rather than treatment differences, researchers reported in the July 24/31 issue of the Journal of the American Medical Association.
“For 20 years healthcare investigators in the United States have been keenly aware of racial disparities in survival among women with breast cancer,” wrote Jeffrey H. Silber, MD, PhD, of the Childrens Hospital of Philadelphia, and colleagues. “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.”
The researchers examined the extent of the racial differences in breast cancer survival in the Medicare population and the reasons for any disparity. The study compared 7,375 black women, ages 65 and older, who were 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 sites in the SEER-Medicare database.
The black patients were matched to one of the three white control populations using 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).
The researchers found the absolute difference in five-year survival (blacks, 55.9%; whites, 68.8%) was 12.9% in the demographics match, and remained unchanged between 1991 and 2005. After matching on presentation characteristics, the absolute difference in five-year survival was 4.4%. The difference was 3.6% lower for blacks than for whites 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 days versus 22.5 days. Blacks also were more likely to have long delays in treatment: 5.8% did not initiate treatment within the first three months from diagnosis, compared with 2.5% of white patients.
Blacks 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.
The researchers found large differences in the way black and white patients presented as a cohort. For the demographics match, 80.5% of black patients had evidence of at least one primary care visit, compared with 88.5% of white patients. Black patients also had significantly lower rates of screening for breast cancer (23.5% vs. 35.7%), colon cancer and cholesterol.
“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.”
Study abstract: http://jama.jamanetwork.com/article.aspx?articleid=1719739.