Race and Efficacy of Monoclonal Antibodies in Multiple Myeloma

There was no significant difference in response to therapeutic monoclonal antibodies between African Americans and Caucasians with multiple myeloma, according to the results of a small study published in Cancer. However, data did show that African Americans treated with either daratumumab or elotuzumab were more likely to present with more advanced stage disease.

“This study aligns with previous observations showing that African American patients present with later stage disease,” wrote Sarah Chehab, PharmD, of Emory University Hospital, Atlanta, and colleagues.

Chehab and colleagues conducted the study to determine if there were race-based differences in a population of patients at Emory treated with single-agent daratumumab (n=46) or elotuzumab, lenalidomide, and dexamethasone (n=34). 

The study included 80 patients. In the daratumumab arm, 17 patients were African American, for elotuzumab, there were 9 African American patients. Advanced stage was significantly more likely for African American patients treated with daratumumab (P = .013) and elotuzumab (P = -.048) than Caucasians, but all other baseline characteristics were similar.

There was no significant difference in response to treatment for Caucasian patients compared with African American patients treated with daratumumab (37.9% vs 11.8%; P = .090) with similar response rates also seen in patients treated with elotuzumab (60% vs 44%; P = .462).

Time to best response and duration of treatment were also similar between African American and Caucasian patients assigned to either drug.

Finally, no significant difference in toxicity for daratumumab was found between African American and Caucasian patients. Some common potential immune-related adverse events occurring in both arms were fatigue (39%), back pain (30%), and infusion reactions (40%). African Americans were significantly more likely to experience back pain of any grade during elotuzumab (P = .017), which the researchers wrote is likely a reflection of more advanced disease.

Additionally, anemia was associated with response to daratumumab (P = .02). No patients without anemia responded to treatment with daratumumab at 2 months.

“In our analysis, patients who did not respond did not have anemia, and this suggests that the response to single-agent daratumumab may be more robust in those with more advanced disease, a finding previously unreported,” the researchers wrote.

In an interview with Cancer Network, C. Ola Landgren, MD, PhD, Chief of the Myeloma Service at Memorial Sloan Kettering Cancer Center, New York, pointed out several differences historically seen in patients with multiple myeloma of African descent – whether from Africa, the Caribbean, or African American – and white patients.

"An earlier age at onset, double the incidence of disease, but with a similar conversion rate from the precancerous monoclonal gammopathy of undetermined significance to multiple myeloma. Studies have also shown that African Americans have less access to newer drugs, a reflection of an overall worse access to care," he said.

“This study was only a small study with virtually no difference in response between African Americans and [Caucasians] because this type of small study does not have the statistical power to detect that difference,” said Landgren.

However, he said that this study is an important one because it is one of the few studies to look at racial disparities in patients with multiple myeloma and that its results should be viewed mostly as confirmative.