showing multiple myeloma
Blacks may be twice as likely as whites to develop multiple myeloma (MM) because they are more likely to have monoclonal gammopathy of undetermined significance (MGUS), according to research published in Leukemia.
In a US-wide study, researchers found that MGUS is more common in blacks than in whites or Hispanics.
And the type of MGUS seen in the black population is more apt to have features associated with a higher risk of progression to full-blown MM.
The study also revealed different rates of MGUS in different parts of the country, which suggests there may be an environmental component to the racial disparities.
“We have known for a long time that there is a marked racial disparity in multiple myeloma, but the big question has been why that disparity exists,” said study author Vincent Rajkumar, MD, of the Mayo Clinic in Rochester, Minnesota.
“We suspected it may be genetic or it may be environmental. We also thought that the predisposing factor is more common, or it may be that the predisposing factor progresses to cancer much more quickly. We found that the answer is all of the above.”
A number of studies have investigated the prevalence of MGUS in various populations. The most prominent took place in the predominantly white community of Olmsted County, Minnesota. There, researchers estimated that MGUS occurred in approximately 3.2% of individuals aged 50 and older.
In the current study, Dr Rajkumar and his colleagues set out to determine the prevalence of MGUS in blacks and Hispanics, as well as whites in other parts of the country. They analyzed stored serum samples of 12,482 people older than 50 years of age taken from the National Health and Nutritional Examination Survey.
By examining the M protein present in each sample, the researchers assessed both the prevalence of MGUS and its likelihood for progression. They found that the prevalence of MGUS was significantly higher in blacks (3.7%) compared with whites (2.3%) or Hispanics (1.8%), as were features that posed a higher risk of progression to MM.
The researchers were surprised that the prevalence of MGUS in whites in their national sample was significantly lower than the rates previously reported for Olmsted County. However, when they broke down the national numbers into geographic regions, they found that people living in Northern and Midwestern states have a higher incidence of MGUS than those living in Southern and Western states.
“We would have missed this geographic difference if we hadn’t looked at the whole country,” Dr Rajkumar said. “This is the largest study of its kind and the first to look at MGUS in a sample of the entire US population.”
Dr Rajkumar and his colleagues are now investigating the underlying causes of these geographic variations to see if they can identify the genetic and environmental factors contributing to the risk of MGUS. They are also repeating their experiments in samples from individuals under age 50 in an effort to pinpoint when the risk of MGUS and, ultimately, MM begins.
