Household income and education levels may play a bigger role than race or ethnicity in whether patients survive the bone marrow cancer multiple myeloma, a U.S. study suggests.

Lots of previous research points to worse cancer survival odds for people of color. But this disparity might be due in large part to class issues like the type of insurance and access to care, the current study concludes.

"Race or ethnicity is mostly a marker for social factors such as poverty, insurance status, education level, etc. which is why we see that ethnic minority individuals experience worse health and health outcomes," said Roshan Bastani, director of cancer disparities research at the University of California, Los Angeles Jonsson Comprehensive Cancer Center, in email to Reuters Health.

"It is not that race or ethnicity does not influence survival. Rather, the effect of race or ethnicity on survival is mostly explained by the negative social factors that are more common among racial and ethnic minority groups," said Bastani, who wasn't involved in the study.

Multiple myeloma is relatively rare; in the U.S., the lifetime risk of getting this type of cancer is 1 in 143, and the disease causes less than 13,000 deaths each year, according to the American Cancer Society.

Less than 1 percent of cases are diagnosed in people younger than 35.

Black people are twice as likely to get this type of cancer as white people, though the reasons driving this aren't clear, according to the cancer society.

Recent treatment for these tumors, which form in a type of white blood cell, have improved survival odds for white patients much more than for black patients, researchers of the current study note in the journal Cancer.

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For the study, Dr. Luciano Costa, of the University of Alabama at Birmingham and colleagues examined cancer registry data on more than 10,000 U.S. patients diagnosed with multiple myeloma before age 65.

At the time of their diagnosis, half of the patients were at least 57 years old. Almost two-thirds were married, and most had health insurance.

Factors that influenced survival odds more than race and ethnicity included marital status, income, and insurance status, the study found.

For example, an unmarried patient who lived in a low-income county and received insurance through Medicaid, the U.S. health program for the poor, was 25 percent less likely to survive four years after diagnosis than a married person the same age with private insurance living in a more affluent community, the study found.

Without any socioeconomic disadvantages, about 71 percent of patients survived at least four years, the study found.

With one strike against them, such as Medicaid coverage instead of private insurance, four-year survival odds dropped to about 63 percent. With two strikes - for example being unmarried and living in a poor community - four-year survival odds dropped to about 53 percent.

Add a third strike - unmarried on Medicaid in a poor neighborhood - and overall four-year survival odds dropped again, to less than 47 percent.

"This finding strongly suggests that there is a huge disparity in outcomes that could potentially be overcome by improving access and affordability of treatments," Costa said in an emailed statement.

Limitations of the study include a lack of details on the exact type of multiple myeloma patients had and how advanced tumors were at the time of diagnosis, the authors note.

"The authors conclude that race does not play a role in survival once you take into account other socioeconomic factors such as insurance status and neighborhood income," said Lauren Teras, strategic director of hematologic cancer research at the American Cancer Society in Atlanta, Georgia.

"However, this paper also shows that in one group this is not true; in patients with the highest expected survival-those who are married, insured, and live in higher income areas-black patients were at a higher risk of dying than were white patients," Teras, who wasn't involved in the study, said by email.

"There is something more complex going on that we do not understand," Teras added.