As compared with White individuals, minorities often face higher barriers to cancer care. Racial and ethnic disparities in patients with solid tumors, particularly those of the prostate and breast, have been well documented. Hematologic malignancies are less common, but an increasing number of studies have documented disparities within this subgroup of cancer, particularly among Black and non-White Hispanics. An increasing armamentarium of therapeutics, including novel chemotherapy agents and targeted molecular, cellular, and immunologic therapies, has highlighted the need for understanding and exploring the differences in care as well as biology, which may lead to disparate outcomes.
Courtesy NIAID
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Overall, an estimated 186,400 people living in the United States are expected to be diagnosed with leukemia, lymphoma, or myeloma in 2021, and new cases of hematologic malignancies are expected to account for 9.8% of the estimated 1,898,160 new cancer cases diagnosed this year.1
The underlying reasons for disparities are highly complex and multifactorial, and clinicians must consider how the biologic, clinical, demographic, and socioeconomic characteristics of their patients interact. All of these factors can play a role in prognosis and/or access to care.
Disparities in leukemia
Leukemia is a heterogeneous group of diseases affecting both children and adults, but during the past few decades survival rates have steadily improved, particularly among children. Response to therapy and prognosis do vary among leukemia types, but one large analysis reported that there were overall improvements in survival seen across racial/ethnic groups, most age groups, and genders during a 40-year period.2
From 1973 through 2014, survival trends were assessed across four leukemia types: acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and chronic lymphoid leukemia (CLL). After stratifying survival for each leukemia type by race/ethnicity, improvement rates were not uniform among all groups.
For example, there were substantial improvements of leukemia-specific survival in 2010-2014 among Black (81.0%) and Asian (80.0%) patients with CML, as well as younger patients (20-49 years) with CLL (96.0%). But in contrast, Black patients, those with AML, and individuals over the age of 75 years experienced the lowest improvement in survival.
Studies have found that Hispanics have increased rates of ALL and acute promyelocytic leukemia (APL), but lower rates of AML, as compared to Whites. They also tend to be diagnosed at a younger age and have poorer overall survival.3
Demographics may also play a role, as Hispanics born outside the United States had a higher incidence rate of APL versus U.S.-born Hispanics (incidence rate ratio, 1.79; 1.11-2.94). Thus, the higher incidence rates of increased B-cell ALL may be due to heritable genetic factors, while APL may also be attributable to environmental exposures.4
Hispanics living on the Texas-Mexico border were also found to have a higher incidence of chronic myeloid leukemia (RR, 1.28; 95% CI, 1.07-1.51; P = .02) and acute myeloid leukemia (RR, 1.17; 95% CI, 1.04-1.33; P = .0009) as compared with Hispanics living elsewhere in Texas5 AML and CML were more likely to be observed in patients who resided in this border region, and those with ALL, AML, and CML had worse outcomes compared with Hispanics living elsewhere in Texas. In addition, both Hispanic and non-Hispanic patients along the border have a worse prognosis for ALL than patients in other areas of Texas.
“We don’t yet understand if the differences are due to nonbiologic factors, or if biology plays a role because of the more aggressive disease that we’re seeing,” said study author Anna Eiring, PhD, an assistant professor at Texas Tech University, El Paso. “This is a medically underserved region, and even though we are a safety net hospital, many of the Hispanic patients don’t have health insurance.”
They also tend to have worse socioeconomic status compared with non-Hispanic populations, and there may also be lifestyle and environmental factors. “Exposure to environmental toxins may also play a role, as many work in jobs that could put them at risk,” she said. “Lifestyle factors may also play a role.”
AML is a hematopoietic disorder that is characterized by numerous cytogenetic and molecular aberrations, with poor overall survival. Researchers found that Black patients had shorter survival than White patients, based on an analysis of Surveillance Epidemiology and End Results (SEER) Program data, and performing and performed mutational profiling of 1,339 patients with AML treated on frontline Alliance for Clinical Trials in Oncology (Alliance) protocols.6 The disparity was especially pronounced in Black patients under 60 years old, after adjustment for socioeconomic (SEER) and molecular (Alliance) factors. Black race was an independent prognosticator of poor survival.
“Based on our analyses in Black and White AML patients under the age of 60 years, we believe that a differential impact of molecular aberrations, specifically AML-associated gene mutations, contribute to the observed survival disparities,” said study author Ann-Kathrin Eisfeld, MD, an assistant professor in the division of hematology at the Ohio State University, Columbus, and a member of the leukemia research program at the university’s comprehensive cancer center, the James. “For example, NPM1 mutations seem to lack the known positive prognostic impact we are used to seeing in previous studies with White AML patients.”
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She noted that when looking at molecular prognosticators just within Black AML patients, researchers found that FLT3-ITD and also IDH2 mutations were associated with poor overall survival. “While FLT3-ITD is a known adverse prognosticator, the significant impact of IDH2 mutations was surprising to us and is currently being further explored,” said Dr. Eisfeld.
“In general, however, it can’t be highlighted enough that while this study suggests an impact of somatic tumor genomics that needs a lot more attention and investigation and ideally, also prospective studies, structural racism and its impact is still the problem,” she emphasized. “It’s the ‘elephant in the room’ and the major factor that needs to be addressed in order to improve and overcome these survival disparities.”