Differences in breast cancer survival rates among black and white women have barely budged in the last two decades, researchers reported in the July 24/31 issue of JAMA. Demographics, health and tumor biology account for most of the difference, they found. Specifically, black women had less access to primary care and breast cancer screening.
Although researchers are well aware of survival disparities among women with breast cancer, they have not yet determined the causes.
Jeffrey H. Silber, MD, PhD, of the Center for Outcomes Research at The Children’s Hospital of Philadelphia, and colleagues sought to determine if the disparity can be attributed to differences in presentation characteristics at diagnosis or differences in treatment.
The researchers mined the Surveillance, Epidemiology and End Results (SEER)-Medicare database and identified 7,375 black women aged 65 years and older diagnosed with breast cancer between 1991 and 2005. They matched these women with three sets of 7,375 white control patients.
Silber and colleagues analyzed outcomes by demographics, presentation characteristics (including comorbid conditions and tumor biology) and treatment.
The absolute 5-year survival rate for black women was 55.9 percent compared with 68.8 percent for white women. The 12.9 percent difference held steady between 1991 and 2005.
When Silber and colleagues matched women on presentation characteristics, they found an absolute difference in 5-year survival of 4.4 percent. A total of 87.4 percent of black women received treatment compared with 91.8 percent of white women. Time from diagnosis to treatment was 29.2 days for black women vs. 22.8 days for white women.
In addition, although use of anthracyclines and taxols was lower among black women and use of breast-conserving surgery without other treatment was more frequent for black women, differences in treatment accounted for only 0.81 percent of the survival difference.
On the demographics match, 80.5 percent of black women had at least one primary care visit compared with 88.5 percent of whites. Black women also had significantly lower rates of screening for breast cancer, colon cancer and cholesterol.
“Most of the difference is explained by poorer health of black patients at diagnosis, with more advanced disease, worse biological features of the disease, and more comorbid conditions,” wrote Silber et al, who noted, “Treatment disparities might matter more if blacks were diagnosed with less advanced cancers.”
Unless differences in presentation can be addressed, it may be difficult to eliminate the racial disparity in breast cancer survival, the researchers concluded.