Association between Clinical Presentation of Multiple Myeloma, Immunoglobulin Isotypes, and Cytogenetic Risk Groups

Introduction:

In multiple myeloma (MM), chromosomal abnormalities (CAs) are valuable in risk stratifying patients and predicting disease free survival. While immunoglobulin isotypes have historically contributed to MM staging, more recently established classifications of CAs have allowed for a revised staging system that better predicts disease behavior. In this retrospective study, we hypothesized that CAs correlate with disease characteristics including immunoglobulin heavy chain isotype, degree of bone marrow infiltration (PC%), and end-organ damage.

Methods:

MM patients diagnosed between 2013 to 2019 were included in this retrospective chart review using electronic records from two distinct sources: (1) 442 patients from an independent pathology database and (2) a validation cohort composed of 110 patients from our institution. CAs were stratified by Mayo mSMART 2.0 criteria into standard, intermediate, and high-risk groups (Mikhael et al. Mayo Clin Proc 2013). End-organ damage was defined as the presence of lytic bone lesions, anemia, hypercalcemia, or renal failure on clinical presentation. Within each cohort, associations between categorical variables were made using the chi-squared test or Fisher's exact test, as deemed appropriate. The Mann-Whitney test was used to compare between groups for continuous variables. A result was considered statistically significant at the p<0.05 level of significance. All analyses were performed using SAS version 9.4 (SAS Institute Inc., Cary, NC).

Results:

552 MM patients were included in the study. Multi-variate analysis revealed that del(13q14), dup(1q21), t(4;14), trisomy (11q13), del(16q23), and hypodiploidy were associated with a significantly higher PC%, whereas kappa light chain only (LCO) disease was associated with a lower PC%. Higher median PC% was found when comparing the intermediate to standard CA risk group. IgA isotype was associated with intermediate risk CAs including del(13q) and standard risk CAs including t(11;14), while IgG isotype was associated with dup(1q21), and kappa LCO disease correlated with a higher rate of higher risk CAs including deletion of p53 at 17p13 and dup(1q21). With regard to clinical presentation, lytic lesions were more frequent in patients with normal cytogenetics and trisomy 11 and less frequent in IgA isotype, whereas the presence of anemia on presentation correlated with IgA isotype. Renal failure was associated with MAF translocations including t(14;16), a high-risk CA.

Conclusions:

We demonstrate that a relationship exists between specific CAs, immunoglobulin isotypes, and clinical presentations in MM. Our data indicate that IgA isotype is significantly associated with intermediate-risk cytogenetics including del(13q) and anemia on presentation, and that light chain disease and renal failure correlate with high risk CAs including del(17p13). These associations between biological and clinical features further support the concept of divergent cytogenetic evolution in MM as being an underlying factor leading to distinctive disease presentations.