Black breast cancer patients are more likely to die than White patients, regardless of the type of cancer, according to a new study called Life After Cancer Epidemiology and Pathways.
These results suggest that the lower survival rate among Black patients is not solely because they are more often diagnosed with less treatable types of breast cancer, the researchers said.
For more than six years, the researchers followed nearly 1,700 breast cancer patients who had been treated for Luminal A, Luminal B, basal-like or HER2-enriched breast cancer subtypes. During that period, about 500 of the patients died, nearly 300 of them from breast cancer.
Blacks were nearly twice as likely as Whites to die. The researchers also found that Black patients were less likely than Whites to be diagnosed with either the Luminal A or Luminal B breast cancer subtypes.
"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," said study author Candyce Kroenke, M.P.H., Sc.D., research scientist at Kaiser Permanente Division of Research in Oakland, Calif.
Kroenke and her colleagues found, however, that lower survival among Black patients was consistent across breast cancer subtypes. Black patients were 2.3 times more likely to die from the Luminal A breast cancer subtype compared with White patients; 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."
Kroenke says there is very little research on risk factors and the less common subtypes, so consequently "we don't really know" why African American women are frequently diagnosed with less treatable breast cancer subtypes. "In one study, Marilyn Kwan found that obesity was positively related to Triple Negative breast cancer. Obesity is more common in African American women and might have explanatory power," continued the researcher.
Additionally, although Black women tend to be diagnosed at a later stage, Kroenke says while this challenge does account for some of the disparity, it does not to cover all of it.
Kroenke says there are many reasons why African American women have worse breast cancer mortality rates some known and others not: differences in co-morbity; aggressiveness of tumors, breast cancer subtype differences, potential treatment differences, etc."
According to the Susan G. Komen for the Cure website, most breast cancers are Luminal A tumors. These cells look the most like the cells of breast cancers that start in the inner (luminal) cells lining the mammary duct.
Luminal B tumors have cells that look like those of breast cancers that start in the inner (luminal) cells lining the mammary ducts.