Though black patients have an incidence of multiple myeloma (MM) that is twice that of white patients, on average their overall survival is better. Cytogenetics play an important role in predicting treatment response and, as the authors of a recent British Journal of Haemotology article hypothesized, if racial differences in cytogenetics exist, they could affect the efficacy of certain therapies across different racial populations.
To identify potential racial differences in MM-associated chromosomal abnormalities, Brandon J. Blue, MD, of the Division of Oncology at the Washington University School of Medicine in St. Louis, Missouri, and colleagues conducted a retrospective cohort study of 813 patients from the U.S. Veterans Health administration (VHA) central cancer registry who were diagnosed with MM between October 1, 1998, and December 31, 2009. The final cohort included 228 black and 585 white patients.
Within this patient cohort, 704 patients (87%) had normal cytogenetic profiles, an isolated Y chromosome deletion, or no mitotic activity. Complete results of the cytogenetic abnormalities in black and white patients are seen in the TABLE, with no differences in hypo- or hyperdiploidy, or in deletion in chromosome 13q.
There was no difference in age-adjusted survival based on race (hazard ratio = 0.90; 95% CI 0.72-1.14).
“This is the largest investigation of racial disparities in MM cytogenetics to date and, contrary to our
hypothesis, we did not find a significant difference in metaphase cytogenetics between black and white patients,” Dr. Blue and co-authors wrote. Based on these data, the better prognosis experienced by black patients is not attributable to racial differences in cytogenetics, they added.
Dr. Blue and colleagues also proposed that, since there appear to be no major race-based differences in the malignant plasma cells, racial differences in MM incidence may be driven by other factors, such as differences in environmental exposures, age, or coexisting diseases: In this patient population, black patients were significantly younger than white patients (mean age = 62.2 vs. 66.6 years; p<0.0001), but had a significantly higher comorbidity burden (mean Charlson score = 3.1 vs. 2.6; p=0.036).
A limitation of the study is the lack of fluorescence in situ hybridization (FISH) data for most patients. “The low frequency of cytogenetic abnormalities is attributable to the historic use of routine cytogenetics instead of FISH testing in the VHA,” the authors noted. They suggested that future research should examine how race may affect genetic differences in plasma cell malignancies by including a comparison of FISH testing or genomic sequencing results.
Blue BJ, Luo S, Sanfilippo KM, et al. Race-based differences in routine cytogenetic profiles of patients with multiple myeloma. Br J Haematol. 2016 February 16. [Epub ahead of print]
|TABLE. Chromosomal Abnormalities Among Black and White Patients|
|Black patients (n=228)||White patients (n=585)||p Value|
|Hyperdiploidy||13 (5.7%)||45 (7.7%)||0.32|
|Deletion of chromosome 13q||8 (3.5%)||21 (3.6%)||0.96|
|Hypodiploidy||4 (1.8%)||12 (2%)||1.00|