Abstract 4233: Racial differences in patterns of cytogenetic abnormalities in multiple myeloma

Introduction: African American (AA) patients with Multiple Myeloma (MM) are diagnosed at younger ages and show an age-adjusted incidence twice as high as that seen in European Americans (EA); however, a study by Waxman et al found higher disease specific survival in AA. A recent study showed differences in chromosomal aberrations between AA and EA, but further work is needed to understand racial differences in cytogenetics through Fluorescent In Situ Hybridization (FISH) using an extensive array of probes. Methods: We identified 470 consecutive patients with MM from the University of Chicago Cancer Cytogenetics Laboratory from October 2003-January 2017. Of those, 127 (22%) patients had abnormal karyotypes and 343 were evaluated by FISH using a panel of 18 probes. Twenty-two patients who self-identified as Hispanic, Multiracial, Asian, or Indian were dropped from the analysis due to low numbers. For the remaining 311 patients, we obtained data on IGH translocations (partner genes included IGH/FGFR3 fusion [t(4;14)(p16.3;q32)]; IGH/CCND1 fusion [t(11;14)(q13;q32)]; IGH/MAF fusion [t(14;16)(q32;q23)]); TP53 loss [17p13.1]; CDKN2C loss [1p32.3]; CKS1B gain [1q21]; ATM losss [(11)(q22.3)11(q22.3)]; trisomy of chromosomes 3, 7, 9, 12, and 15; and chromosome 13 loss or interstitial deletion of 13q. We grouped the FISH results as high (loss of TP53, loss of CDKN2C; CKS1B gain, IGH/MAF fusion), intermediate (IGH/FGFR3 fusion), or standard (Trisomies 3, 7, 9, 15; Gain of TP53, Gain of ATM, chromosome 13 loss) prognostic risk markers. Results: Of 311 patients, 172 (55.3%) are self-reported EA, 130 (41.8%) are AA. Compared with EA, AA patients were more likely to be females (44.8% vs. 59.2%, respectively) and older than 65 years at diagnosis (47.7% vs. 56.2% respectively). Overall, 6.3% of patients were younger than 45 years at diagnosis, but there was no racial difference in the proportion of young patients. Compared with EA, AA patients assessed with standard risk probes were less likely to have standard risk cytogenetic features (48% vs. 66%; p-value=0.02). AA patients showed a lower percentage of hyperdiploidy, 36.5% of AA patients assessed were positive for hyperdiploidy compared with 57.1% of assessed EA (p=0.02). Despite the lower proportion of AA with cytogenetic markers associated with favorable prognosis, there was no significant difference between EA and AA patients in the prevalence of adverse prognostic markers, such as TP53 deletion, IGH/MAF fusions, or CKS1B gain. However, we did observe that AA patients were more likely to have loss of CDKN2C (16.7% vs 3.6%, p=0.02). Conclusions: We found that compared with EA, AA patients are less likely to have cytogenetic features associated with favorable prognosis (i.e. hyperdiploidy), yet AA do not have a higher prevalence of high risk cytogenetics. These findings suggest that cytogenetics alone may not fully explain racial/ethnic differences in MM mortality. [Meytal Chernoff and Madina Sukhanova are co-first authors of this abstract.] Citation Format: Meytal B. Chernoff, Madina Sukhanova, Liz Stepniak, Wei Zhang, Brian C. Chiu. Racial differences in patterns of cytogenetic abnormalities in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4233.