Favorable Responses to Novel Agents for Multiple Myeloma in African American Patients,

Abstract 4213

Multiple myeloma (MM) accounts for 10% of hematologic malignancies in the U.S. African Americans (AA) have twice the risk of developing multiple myeloma and, in previous studies, a higher mortality rate when compared to non-African Americans (non-AA). In recent years, clinical outcomes for patients with MM have improved as a result of new agents, such as immunomodulatory drugs (IMiDs) and bortezomib. However, the therapeutic impact of these new therapies in AA vs. non-AA patients has not been evaluated. In this study, 53 consecutive patients (23 AA, 30 non-AA) with newly diagnosed MM were retrospectively analyzed after induction treatment with thalidomide/dexamethasone (n=22), lenalidomide/dexamethasone (n=8), bortezomib/dexamethasone (n=5), bortezomib/thalidomide/dexamethasone (n=3), lenalidomide/bortezomib/dexamethasone (n=12), or an IMiD plus melphalan (n=3). AA and non-AA patients were comparable for age, immunoglobulin isotype, MM stage of disease, serum β₂microglobulin and albumin levels, and cytogenetic abnormalities including del13 (27% vs. 38%, respectively, p=NS). When measured according to international uniform criteria, the response rate to induction therapy was not statistically different between AA and non-AA patients: complete remission (CR, 22% vs. 21.4%), very good partial remission (VGPR, 26% vs. 21.4%), or partial remission (PR, 43.4% vs. 32.1%). However, the rate of stable/progressive disease following induction therapy was significantly higher in non-AA patients (p = 0.03). Of 53 patients, 34 received high-dose chemotherapy followed by autologous stem cell transplant (ASCT). In this group, the CR + VGPR rate following ASCT was significantly higher in AA compared with non-AA patients (59% vs. 35%, p=0.0007). At a median follow up of 47 months, the relapse rate was 59% in AA and 46% in non-AA patients (p=NS) and the median time to progression (TTP) was 9.1 months in both groups. Five patients (9%) died. All deaths occurred in the non-AA cohort and in 4/5 cases death was due to disease progression. In conclusion, our findings demonstrate that despite their increased disease risk, AA patients with MM have a favorable outcome that is equivalent to that of non-AA patients when treated with IMiDs and/or bortezomib.