Racial Disparity in Patients with Multiple Myeloma Are Blunted in the Era Novel Therapies

Background: Multiple myeloma is the most common hematological malignancy among african americans (AA). Prior studies have shown conflicting results for outcomes based upon ethnicity following autologous stem cell transplantation (ASCT). However, much of this data is older, and predates the use of novel agents such as bortezomib (V), lenalidomide (R) and thalidomide (T).

Methodology: We performed a retrospective analysis of 292 patients (147 AA and 145 Caucasian) treated with novel agents (proteasome inhibitors or immune modulators) and ASCT from 2006 to 2012 at the Winship Cancer Institute of Emory University to evaluate the impact of ethnicity on outcomes.

Results: Baseline characteristics such as stage (International Staging System, ISS), presence of lytic lesions or plasmacytomas, immunoglobulin subtype, and cytogenetic risk category at presentation, were comparable between AA and white patients. Among AA, 112 (76.19%) patients received bortezomib containing regimens (VRD: 34.8%, VTD: 22.3%, VDTPACE:11%, VDD:10%, VD:19% and others bortezomib regimens 8%), 54 (36.7%) patients received lenalidomide (VRD: 34.8% or RD: 11.6%) and 72 (49%) patients received thalidomide (VTD: 22.3% or TD: 11.6%). In white patients 113 (77.93%) received bortezomib containing regimens (VRD: 33.1%, VTD: 17.2%, VDTPACE:9.6%, VDD: 1.4% and VD:11.7% and other bortezomib regimens 1.3%), 69 (47.6%) patients received lenalidomide containing regimens (VRD:33.1% and RD:11%) and 62 (42.8%) patients received thalidomide containing regimens (VTD: 17.2% or TD: 15%). A higher percentage of patients in the white cohort carried the antecedent diagnosis of monoclonal gammopathy in white patients (AA:0 vs white: 4.8%, p=0.007), and as expected, AA patients presented at a younger age when compared with whites (mean age of 55 vs 59 years, respectively, p<0.001). The overall response rate (ORR) of induction in the entire population was 86%, with an >VGPR of 58.8%. No difference was identified in pre-transplant ORR and >VGPR between AA (87.9% and 25.9%, respectively) and white patients (81.54% and 22.4%, respectively, p>0.1). Similarly, the ORR and >VGPR 100 days after transplantation was comparable between both ethnic groups (AA: OR:90.74% and >VGPR:74.07% vs white OR:90.65% and >VGPR: 77.57%, p>0.1). The depth of response after ASCT improved similarly in both groups (AA: 57.3% vs white: 67.7%, p=0.1). When the overall survival and progression free survival where evaluated, we found no significant differences between both cohorts. Factors associated with longer PFS in the population studied include AA race and the introduction of lenalidomide in the induction regimen. In AA patients univariate analysis identified early stage at presentation, indolent disease (prolong time from diagnosis to transplant), optimal pre-transplant response, and pre-transplant use of lenalidomide (HR:0.38 (0.18-0.8), p=0.01) as factors that potentially prolong PFS. Multivariate analysis identified the use of lenalidomide, as part of the pretransplant regimen, to reduce the risk of relapse (HR:0.38 (0.18-0.8), p=0.01) compared to bortezomib use (HR: 5.3 (2.11-11.98), p<0.001). In white patients, univariate and multivariate analysis identified that IgG and kappa light chain MM and indolent disease were factors associated with longer PFS, while history of plasma cell leukemia was related to shorter PFS.

In conclusion, our results showed that novel agents have improved the response rate of both ethnic populations. From our preliminary analysis, it appears the PFS is longer among AA patients, suggesting a potential difference in MM biology of this patient population.