Compared with other racial and ethnic groups across cancer subtypes, black women with breast cancer had significantly worse survival rates.
This suggests that the survival differences are not solely attributable to the fact that black women are more frequently diagnosed with less treatable breast cancer subtypes, according to data presented at the AACR Annual Meeting 2013, held in Washington, D.C., April 6-10.
"The results seem to indicate that although African-American women are more likely to be diagnosed with less treatable subtypes of breast cancer compared with white women, it is not the only reason they have worse breast cancer mortality," said Candyce Kroenke, M.P.H., Sc.D., research scientist at Kaiser Permanente Division of Research in Oakland, Calif.
The researchers obtained participants self-reported race information from mailed questionnaires. They tested samples of the patients tumors to determine their molecular subtype of cancer.
After 6.3 years of follow-up, 499 women had died, 268 of them from breast cancer. Consistent with previous data, black women were nearly two times more likely to have died from breast cancer compared with white women. In addition, black women were less likely to be diagnosed with either the luminal A or luminal B breast cancer subtypes compared with white women.
"African-Americans were more likely to have the hard-to-treat triple-negative breast cancer subtype and had a lower likelihood of having the luminal A subtype, which tends to be the most treatable subtype of breast cancer and has the best prognosis," Kroenke said.
However, the researchers found that poor prognosis among blacks appeared consistent across breast cancer subtypes. Compared with white women, black women were 2.3 times more likely to die from the luminal A breast cancer subtype, 2.6 times more likely to die from the luminal B subtype, 1.3 times more likely to die from the basal-like subtype and 2.4 times more likely to die from the HER2-enriched subtype.
"African-Americans with breast cancer appeared to have a poorer prognosis regardless of subtype," Kroenke said. "It seems from our data that the black-white breast cancer survival difference cannot be explained entirely by variable breast cancer subtype diagnosis."