Racial/ethnic disparities: need more work!

In this issue of Blood, Kirtane and Lee shed light on an important aspect of hematologic malignancies: the issue of racial and ethnic disparities. As pointed out by the authors, such patterns are well documented for solid tumors but less is known about hematologic malignancies. As the American population continues to become more diverse, it is of major importance that outcomes for all racial and ethnic groups continue to improve.¹ 

In their article, the authors dissect patterns of disparity with regard to incidence, survival, and outcomes. They cover the whole spectrum of hematologic malignancies, including acute myeloid leukemia (AML), acute lymphoblastic leukemia, multiple myeloma (MM), non-Hodgkin lymphoma, Hodgkin lymphoma (HL), myeloproliferative neoplasms, and myelodysplastic syndrome (MDS). They address potential underlying causes and discuss future directions for research. Here are a few examples from their article.

The authors emphasize that the National Cancer Institute’s (NCI’s) Surveillance, Epidemiology, and End Results (SEER) database (1999-2008) shows an excess risk of dying among black (12%) and Hispanic (6%) patients with AML compared with non-Hispanic white patients with AML.²  These disparities exist despite an increased prevalence of favorable cytogenetics and a younger age at diagnosis in these minority groups.³  Furthermore, being African American, residing in an area with a high poverty level, and having Medicaid as their only form of health insurance were found to be independent predictors of worse survival in patients with AML.⁴  These patterns of disparities in terms of outcomes are most likely reflections of differences in access to high-quality care in the United States.

From an analysis of 2538 patients with MDS, those who are Hispanic tend to be younger, have worse thrombocytopenia, and have a higher proportion of therapy-related MDS when compared with other minority groups.⁵  In contrast to Hispanic patients with AML, Hispanic patients with MDS have a better median overall survival (47 months) compared with whites (37 months) and African Americans (30 months).⁵  These patterns of disparities suggest that there are biological differences across racial and ethnic groups.

African Americans have a two- to threefold higher risk of developing MM compared with whites.⁶  This is a result of a two- to threefold excess of myeloma precursor disease (monoclonal gammopathy of undetermined significance [MGUS]).⁶  Prior studies have found the risk of progression from MGUS to MM to be very similar between African Americans and whites.⁶  Although African Americans have a higher risk of developing the disease, when it comes to survival outcomes (based on NCI SEER data), African American patients with MM have a better survival than white patients.⁷  On the basis of clinical outcome patterns, data also suggest that access to high-quality care varies across racial/ethnic groups for patients with MM.⁷ 

Black and Hispanic adolescents and young adults have a higher risk of death (62% and 35%, respectively) as a result of HL. They are also more likely to be diagnosed with HL at an advanced stage when compared with whites and Asian/Pacific Islanders. These are again reflections of differences in access to high-quality care.

In addition to reviewing the spectrum of hematologic malignancies, the authors discuss potential causes in depth for observed disparities, including structural barriers to care, variable access, compliance with intensive therapies, and overall disease heterogeneity.

Kirtane and Lee emphasize the fact that recruitment and enrollment of minorities in clinical trials overall is low compared with that for whites. For example, many of the trials leading to the approval of nivolumab for nonsquamous lung and advanced renal cell carcinoma had study populations involving nearly 90% white patients and less than 10% underrepresented minorities.^8,9  They also mention that many of the trials involving immunotherapy for hematologic malignancies do not report the racial demographics of their study populations, so it is worrisome that these trials may be plagued by a similar lack of diversity. Additionally, in MM trials, minorities are known to be underrepresented. This underrepresentation may in turn challenge the generalizability of the results of these clinical trials to minority patients.¹⁰ 

The authors call for more research on the topic of racial and ethnic disparities in hematologic malignancies. Currently, significant disparities in incidence and survival exist for patients diagnosed with hematologic malignancies, yet little is known about the basis for these differences.