NEW YORK (Reuters Health) - Despite receiving similar cancer treatment as other patients, African Americans with a common form of leukemia didn't live as long in a new study that was aimed at understanding the racial disparity in cancer outcomes.
"We don't have an answer" to explain it, said Dr. Alessandra Ferrajoli, the study's senior author and an associate professor of medicine at MD Anderson Cancer Center in Houston.
Though all patients received equal medical treatment, the black patients tended to have chromosome mutations and other characteristics that are known to be linked with a worse prognosis.
It's likely "not related to the treatment," Ferrajoli speculated, "it's probably a different biology."
Previous studies have found that African Americans are more likely to die from cancer than whites (see Reuters Health story of February 5, 2013 here:).
For instance, researchers reported last year that blacks have a greater chance of dying after a kidney cancer diagnosis, despite having better odds of developing a more easy-to-treat form of the cancer.
Other research has shown that black women are more likely to die from breast cancer than white women.
The reasons for these disparities are not certain, but experts have often pointed to delays in diagnosis or treatment resulting from difficulty accessing care or differences in socioeconomic status, Ferrajoli said.
To look at what other differences might exist among patients with blood cancer, Ferrajoli and her colleagues examined medical records from MD Anderson and from Duke University Medical Center in Durham, North Carolina.
Over a five-year period, between 1997 and 2011, more than 1,600 patients were treated for chronic lymphocytic leukemia (CLL), the second most common form of leukemia.
About four out of every 100,000 people in the U.S. are diagnosed with CLL each year.
Of those in Ferrajoli's study, 84 were African American and 1,571 were not.
Her group found evidence that African American patients received the same quality of treatment as the other patients.
However, 56 percent of the African American patients had a complete response to treatment while 58 percent of patients in the other group also went into remission, the researchers report in the journal Cancer.
"We noted that when we treated (African Americans), they will respond in a similar way to the rest of the population, but their responses don't last. They had worse outcomes," Ferrajoli told Reuters Health.
Over years of follow up, the researchers found that 21 percent of the African American patients and nine percent of the other patients died.
In addition, African American patients typically went 36 months without a recurrence of the cancer, while the other patients made it 61 months.
Ferrajoli said there must be some differences in the cancer between African American and other patients to explain why they don't fare as well.
Her team did find differences among the groups at the outset.
Prior to the start of treatment, African American patients were more likely to have factors associated with more difficult CLL cases, such as lower hemoglobin levels and higher rates of a particular chromosome mutation.
But even after taking those issues into account, race continued to be a risk factor for a worse outcome.
"The demonstration that these differences in survival persist even when similar therapies are administered for CLL is a novel finding, and it suggests that (African American) patients may have different disease biology than (non-black) patients," said Dr. Christopher Flowers, an associate professor at Emory University School of Medicine, in an editorial accompanying the study.
Ferrajoli said it will be important to investigate the potential biological explanations so that treatments can be tailored to address these differences.
Her findings don't rule out that non-biological differences might still play a role in other cancers.
"For other diseases, there may be differences in treatment...but not for ours at this point," Ferrajoli said.