Race-Based Differences in Routine Cytogenetic Profiles of Patients with Multiple Myeloma

Background: Multiple myeloma (MM) is a common hematologic malignancy for which standard therapy does not offer a cure. Incidence of MM in African-Americans is twice that of Caucasians, suggesting differences in either environmental or genetic risk factors. Historically, black patients have also had a slightly better prognosis than white patients, suggesting racial differences in prognostic factors such as cytogenetics. Since metaphase cytogenetic profiles are routinely collected in MM patients, we sought to determine if race-based differences in cytogenetics exist, using data from the Veterans Health Administration (VHA) cancer registry.

Methods: Using CPT codes, 88271-88275, 88291, 88299, 88365, 83896, 88237, 88261-88264, 88280, 88283, and 88285, we identified 988 patients with MM diagnosed between 1998 and 2009, who also had standard metaphase cytogenetic analysis performed on a bone marrow specimen at the time of diagnosis (228 Black and 585 White) . Fisher’s exact test was used to assess for race-based differences in the following cytogenetic abnormalities: 13q deletion, Hypodiploidy, Hyperdiploidy, and translocations involving chromosome 14.

Results: Among the 988 patients in the cohort, normal cytogenetic profiles, isolated Y chromosome deletion, or no mitotic activity were observed in 704(71%) patients. Translocations involving the immunoglobulin heavy chain (chromosome 14) (n=4) were uncommonly observed on routine cytogenetics, such that no statistical conclusions could be drawn. Hyperdiploidy was noted in 13/228(5.7%) of the black and 45/585(7.7%) of the white patients (p=0.32). Similarly 13q deletions were detected in 8/228(3.5%) black patients, and 21/585(3.6%) of the white patients (p=0.96). Hypodiploidy was also not significantly different in black 4/228(1.8%) and white patients 12/585(2.0%).

Conclusion: This is the largest study of race-based differences in MM cyogenetics presented to date. We found no significant race-based differences in standard metaphase cytogenetics. Future studies should focus on determining if race-based differences can be discovered using fluorescent in situ hybridization (FISH) or molecular testing not available for this retrospective study. Our study adds to this growing body of evidence suggesting that metaphase cytogenetic differences are not a significant factor in MM outcome disparities.