Comparison of Cytogenetics Between Asian and Caucasian Myeloma Reveal Higher Frequency of Abnormalities Associated with Poor Prognosis in Asian Patients

In multiple myeloma, cytogenetics is informative in only about a third of patients. Despite this limitation, it remains a commonly available laboratory investigation that has prognostic utility and allows detection of global changes including ploidy. While cytogenetics abnormalities in myeloma have been well documented, a direct comparison between Western and Asian patients has not been performed.

Retrospective analysis of 190 newly diagnosed multiple myeloma patients presenting to the National University Hospital Singapore (NUH) between 2000–2009, and 494 newly diagnosed multiple myeloma patients from the Mayo Clinic myeloma database from 2000 to 2005 were analyzed. All abnormalities were logged onto an excel spreadsheet where all cytobands were represented. Gains, losses and structural abnormalities including specific translocations were documented separately. Abnormalities present in 5% or more samples with cytogenetic abnormalities were further analysed and compared between the 2 cohorts using chi-square test. Bonferroni correction is used when multiple comparisons were made.

80/190 (42%) of NUH patients had an abnormal karyotype compared with 180/494 (36%) in the Mayo clinic cohort (not statistically significant p=0.17). Distribution of ploidy status was very similar between the NUH and Mayo cohort with 35% and 27% being hyperdiploid in the NUH and Mayo cohort respectively (p=0.57). In both cohorts, the most common gains are whole chromosome gains involving chromosomes that are commonly trisomic in hyperdiploid myeloma. However, the pattern of trisomies is different between the NUH and Mayo cohort, with trisomies of chromosome 5, 7, and 19 more common in NUH (p-values <0.0001 for all three comparisons). Loss of 1p21was more common in NUH compared with Mayo (9% vs 2%, p=0.01) although loss of chromosome 7 was more common in Mayo compared to NUH (15% vs 0%, p=0.0002). t(11;14) is the most common translocations for both cohorts. Translocations involving chromosome 1 with different partners are also common in both cohorts. However, there are also interesting differences. Rearrangements involving the IgH (14q32) [10% NUH vs 4% in Mayo] and MYC (8q24) [6% in NUH vs 1% in mayo] loci are more common in the NUH cohort. In fact, when MYC translocations with IgH or IgL are included, 9 (11%) cases in the NUH cohort were affected versus 4 (in the Mayo Clinic cohort (p=0.0002). Recurrent rearrangement of 3q27 was observed in 5% of the NUH cohort while no cases were noted in the Mayo cohort. A search of the Mitelman Database of Chromosome Aberrations and Gene Fusion in Cancer (http://cgap.nci.nih.gov/Chromosomes/Mitelman) showed that only 4 out of 1643 Caucasian myeloma karyotype recorded had this abnormality (p<0.0001). 1q21 deletion and MYC rearrangements are associated with poorer prognosis.

From this comparison, the general patterns of cytogenetic abnormalities are similar between Asian and Western patients. The most important difference between Asian patients and western patients was the higher incidence of poor prognostic cytogenetic abnormalities in Asian patients including 1p21 deletion and gene rearrangements involving the MYC gene locus. 3q27 was predominantly seen in the Asian patient cohort and rarely in western patients. This could be a unique feature of Asian myeloma patients and more studies will have to be done to confirm this. These differences may have important implication on outcome of patients in Asian and Western Countries, and also unique biology that could potentially be exploited therapeutically.

Fonseca:Consulting:Genzyme, Medtronic, BMS, Amgen, Otsuka, Celgene, Intellikine, Lilly Research Support: Cylene, Onyz, Celgene: Consultancy, Research Funding.