Real-World Disparities in Daratumumab Utilization for Patients with Relapsed or Refractory Multiple Myeloma (MM)

Introduction

In the last 3 years, 4 new drugs indicated for MM have been approved, positively affecting the prognosis of patients with this disease. While these novel therapies offer therapeutic options to patients who have failed other treatments, adoption of new agents has historically lagged in African Americans, potentially limiting improvement in outcomes for this population. One of the newer drugs is daratumumab, a fully human anti-CD38 monoclonal antibody, first approved in November 2015 to treat relapsed or refractory disease in 3rd and 4th lines of therapy (LoTs). We sought to examine differences in daratumumab uptake stratified by race and identify factors associated with use of this drug in the real world.

Methods

This retrospective cohort study used information from the Flatiron Health (FlH) database, which is derived from pooled electronic health record (EHR) data; Institutional Review Board approval with a waiver of informed consent was obtained. The cohort included 3240 patients followed for MM from 11/16/2015 to 05/31/2018 across the United States and was limited to patients with a confirmed diagnosis of MM, who received at least one LoT starting on 11/16/2015 or later, and who were white or African American. Patients whose start of MM treatment (captured through chart review) was > 30 days before the start of structured activity in the FlH database were excluded as this may indicate missing therapy data. The proportion of LoTs including daratumumab stratified by year of LoT start was plotted for African-American and white patients. P values were calculated using chi-squared and Kruskal-Wallis tests.

Results

African-American patients were less likely to receive daratumumab for any LoT than white patients (12.1% vs. 15.4%, P = 0.041). Daratumumab uptake increased year by year, but net adoption lagged in African-American patients compared to white patients (Figure). For LoTs with a start date in 2015 (after 11/16/2015), 2.0% of those received by African-American patients included daratumumab, compared to 2.5% of those received by white patients. For the first 5 months of 2018 (before 05/31/2018), these percentages increased to 15.8% for African-American patients and 16.8% for white patients. Patients receiving daratumumab for any LoT were more likely to be younger at diagnosis (median age 66 years, IQR: 59-73 years vs. 70 years, IQR: 62-77 years; P < 0.001) and to be followed at academic centers than at community clinics (13.8% vs. 10.4%, P = 0.031). Consistent with previous literature, African-American patients in this cohort were younger at diagnosis than white patients (median age at diagnosis 67 years, IQR: 59-74 years vs. 70 years, IQR: 62-77 years; P < 0.001), and fewer were followed at academic centers (7.3% vs. 11.8%, P = 0.001).

Conclusions

While the absolute difference in daratumumab utilization is modest, this disparity has persisted over the last 3 years, with African-American patients lagging behind white patients. This trend may indicate inequities in access to and utilization of expensive newer treatments, which is particularly notable because of the higher incidence of MM in African Americans. Our study was limited as it did not control for gender, regional differences, cytogenetics, or insurance type. Further research is also required to determine if the observed treatment differences are associated with differences in clinical outcomes. To our knowledge, this is the first study to examine racial disparities in daratumumab uptake using recent, EHR-derived data from the real world.

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