Multiple Myeloma Precursor Found to Be More Common in African-Americans

Study finds significant racial and geographic disparity in prevalence of monoclonal gammopathy of undetermined significance.

African-Americans are already known to have a significantly higher risk of developing multiple myeloma (MM) than other racial groups, and now researchers have uncovered an increased prevalence by race of a precursor to the disease as well.

According to the results of a study published online on February 21, 2014, in Leukemia, monoclonal gammopathy of undetermined significance (MGUS) is linked to a marked racial disparity in the incidence of multiple myeloma.

“African-Americans have a twofold or greater risk for MM compared with whites,” the authors write. ”The higher incidence of MM in blacks may result from a higher prevalence of the precursor lesion, MGUS, or an increased risk of progression of MGUS to MM.”

The researchers examined samples and data collected from the National Health and Nutritional Examination Survey (NHANES) for the time periods of 1988 through 1994 and 1999 through 2004. Out of 12,482 people included in the study (2331 non-Hispanic blacks, 2475 Mexican-Americans, 7051 whites, and 625 “others”), MGUS was identified in 365 participants for an overall prevalence rate of 2.4%. Of the 365 cases of MGUS, 90 participants were black (25%), 214 were white (58%), and 52 were Mexican-American (14%).

In addition to a higher overall prevalence of MGUS identified in African-Americans, researchers also note the elderly black population above 80 years of age had a prevalence rate of 8.6%, which is double the rate of whites the same age.

“Across all age groups, the prevalence of MGUS in blacks was similar to that seen in whites and Mexican-Americans a decade older,” the authors write. “These results suggest racial heterogeneity early in the carcinogenic disease pathway, while also consistent with the younger age distribution seen among blacks compared with whites in MM.”

The study also indicates that MGUS in the black population is more likely to progress to MM than it is in other racial groups.

In addition to racial disparities, researchers note a geographic disparity in the prevalence of MGUS between the North and Midwest of the United States compared with the South and West. Researchers looked at a large population-based study of MGUS in the homogenous white population in Olmsted County, Minnesota, where MGUS prevalence is estimated at 3.2% of those older than 50.

The prevalence of MGUS in whites nationally (2.3%) is significantly lower than it is in Olmsted County (3.2%). In addition, the MGUS rate among patients older than 50 (4.0% in men and 2.7% in women) in Olmsted County is greater than the NHANES-weighted results nationally (2.8% in men and 2.0% in women), the authors note.

“[T]he death rate from MM is much higher in Minnesota than in most other regions of the country,” the authors write. “Because MM is a highly fatal disease, these deaths are probably a reasonable indicator of MM incidence, and, because MM is almost always preceded by MGUS, this suggests that the regional discrepancies in MGUS prevalence that we have observed are real.”

Advancing age, male sex, increased BMI, and low socioeconomic status were also found to increase the risk of MGUS, and the researchers noted that further study is needed of racial and geographic disparities in the prevalence of the MM precursor.

“Molecular analyses are warranted in order to further elucidate the disparity of cytogenetic subtypes among the races and to evaluate possible differences in prognosis and progression within racial and ethnic groups,” the authors write. “Moreover, this disparity may affect counseling efforts.”