Improved Survival in African American Patients Undergoing Autologous Transplant for Multiple Myeloma in the Chemotherapy and Novel Agent Era

African Americans (AA) have a 2- to 3-fold higher incidence of multiple myeloma (MM) when compared to other racial groups. Evidence suggests that there may be differences in the biology of MM, which confer a more favorable prognosis in AA patients. Prior studies are conflicted as to whether AA patients achieve equal or improved outcomes compared to non-African American (non-AA) patients. Our purpose was to evaluate the impact of AA race on outcomes of MM patients undergoing ASCT at a single center in both the chemotherapy and novel agent era.

One hundred and twenty-nine patients who received melphalan 200 mg/m2 and ASCT between 2000 and 2013 were included in the analysis. Sixty-one (47%) patients were African-American and 68 (53%) were non-AA. Baseline characteristics including age, FISH, cytogenetics, paraprotein subtype, median number of prior therapies and International Staging System (ISS) stage were similar between racial groups. Overall, 77 (60%) patients received any novel agent prior to transplant and 52 (40%) received only chemotherapy. More non-AA patients were male (59% vs. 38%, p=0.02), received initial induction with a proteasome inhibitor (59% vs. 28%, p=0.0007), and were treated with post-ASCT maintenance therapy (41% vs. 23%, p=0.008). Time from diagnosis to ASCT in AA patients was 10 (range: 4-144) versus 8 (range: 3-54) months in non-AA patients (p=0.01). The ASCT hospital course was similar between both groups with no significant differences in time to neutrophil and platelet engraftment as well as the duration of hospitalization. Additionally, there was no significant difference in the extra-hematologic toxicity between the two groups including the incidence of diarrhea, mucositis, and infection.

Response was measured using the International Myeloma Working Group criteria and was assessed immediately prior to transplant and between 90 to 180 days after transplant. No differences were observed in pre-transplant (p=0.13) or post-transplant (p=0.28) response rates between the two groups. African American patients had a significantly improved median OS compared to non-AA patients (not reached vs. 108 months, p=0.03). We further stratified analyses of OS by those treated in the chemotherapy versus novel agent era. Improved OS was observed in both the chemotherapy (93 vs. 68 months, p=0.02) and novel agent (not reached vs. 79 months, p=0.01) treatment era. In a multivariate Cox proportional hazards model, AA race was associated with improved overall survival (adjusted HR 0.30, 95% CI 0.11 to 0.81; p=0.017).

Multiple myeloma has one of the most apparent ethnic disparities in incidence and outcomes among cancers. In our study, AA patients had a longer time to transplant and received less proteasome inhibitor-based induction and post-ASCT maintenance suggesting disparities in access to care. Despite these differences in treatment, we observed improved overall survival after ASCT compared to non-AA patients. We demonstrated this improved OS in patients who had received either chemotherapy or novel agents prior to ASCT. These findings provide further evidence for more favorable outcomes among AA patients. One explanation could be a difference in disease biology that may result in a lower risk disease. Investigation of these biologic differences between AA and non-AA MM patients may increase our understanding of the pathogenesis and future treatments of myeloma.