Racial Disparities Seen in Survival Among Pediatric Patients With Acute Lymphoblastic Leukemia

White patients with acute lymphoblastic leukemia (ALL) had 5-year event-free survival (EFS) rates that were significantly higher than those seen among Hispanic and Black patients in a study of nearly 25,000 young people by the Children’s Oncology Group (COG). The findings were presented Saturday during the 63rd Annual American Society of Hematology (ASH) Meeting and Exposition, taking place in Atlanta and online.

Of note for policy makers, children in the United State with Medicaid coverage have lower survival rates than those not in Medicaid. But more surprising was the fact that children in the study living outside the United States—in countries such as Canada, Australia, or New Zealand—had 29% reduced risk than White children in the United States.

Sumit Gupta, MD, of The Hospital for Sick Children in Toronto, Canada, said that biological or genetic factors accounted for some of the gap in survival rates, but not all. “Our study shows that race and ethnicity-based disparities continue to exist and are substantial,” Gupta said. “All groups do well overall, but some do substantially better than others.”

For the study, investigators examined a cohort of 24,979 children, adolescents, and young adults with ALL. Patients who were non-Hispanic White accounted for 13,872 (65.6%) of the group, followed by 4354 (20.6%) who were Hispanic and 1517 who were non-Hispanic Black.

A little more than a quarter were covered by US Medicaid (27.8%), or 6944 patients.

The 5-year EFS was 87.4% (±0.3%) among non-Hispanic White patients vs 82.8% (±0.6%) for Hispanic patients (HR 1.37, 95% CI: 1.25­­­­­­­­­­­­­­­-1.49; P < .0001); and 81.9% (±1.2%) for non-Hispanic Black patients (HR 1.45, 95% CI: 1.28-1.56, P < .0001). Investigators reported that outcomes for non-Hispanic Asian patients were similar to White patients.

Insurance status. US patients on Medicaid had worse outcomes compared with other US patients. Medicaid was associated with a 5-year EFS of 83.2% vs 86.3% for US patients not on Medicaid, (HR 1.21, 95% CI: 1.12-1.30; P < .0001). Patients outside the US who were in this cohort had even better outcomes in 5-year EFS, 89.0% (HR 0.78, 95% CI: 0.71-0.88; P < .0001). However, this group was small relative to the overall group at 3151 patients.

Explanations for the findings. Gupta said that having identified these disparities, the investigators sought to identify how could be explained by imbalances in other prognosticators. “For example, socioeconomic status did, unsurprisingly, vary by race ethnicity—50% of Hispanic patients were on Medicaid vs only less than 20% of non-Hispanic White patients,” he said. “Similarly, disease prognosticators also vary by race and ethnicity.”

Investigators found that the worse outcome in EFS among Hispanic patients was substantially attenuated by the addition of disease prognosticators, with HR reduced from 1.37 to 1.17; this was further attenuated by including socioeconomic status, or SES (HR 1.11).

By contrast, investigators wrote, “the increased risk among non-Hispanic Black children was minimally attenuated by both the addition of disease prognosticators and subsequent addition of SES (HR 1.45 to 1.38 to 1.32).”

Notably, this process produced patterns in which “disparities in overall survival were wider than those seen in event-free survival,” Gupta said.

During the session, participants brought up possible confounders such as increased obesity rates or pulmonary arterial hypertension rates among Hispanic patients. Each of these may tell part of the story, and all are worth exploring. 

“It is possible that there is residual confounding by disease prognosticators here that we did not fully account for,” he said. “However, that seems unlikely to explain the full medical experience we're seeing, so that we are then left with somewhat uncomfortable mechanisms to talk about such as differential access to care, differential quality of care.

“And when we use the unfortunately politically charged ‘systemic racism’ or another term, the possibility that even pediatric oncology health care systems are systematically delivering difficult care to patients across racial groups.”

B-ALL vs T-ALL. A key difference uncovered by this process is fact that disparities are largely driven by ALL of B-cell lineage, rather than T-cell lineage, Gupta noted, as he presented a slide showing the differences in the data.

During the press briefing, Gupta noted, “The treatment is pretty similar and delivered by the same centers.” Typically, a patient receives 8 to 10 months of intensive therapy followed by 18 to 24 months of lower intensity or maintenance treatment. This second phase is where investigators may need to look for clues to explain survival gaps, he said.

“There isn't quite as much control and not quite as much monitoring that oncologists will do,” he said. “Maybe if we're delivering different care across these ethnic and racial groups and maintenance, that might explain some of those findings.”

Reference

Gupta S, Teachey DT, Devidas M, et al. Racial, ethnic and socioeconomic factors result in disparities in outcome among children with acute lymphoblastic leukemia not fully attenuated by disease prognosticators: A Children’s Oncology Group Study. Presented at: the 63rd Annual American Society of Oncology Meeting and Exposition; Atlanta, GA; December 11, 2021. Abstract 211. https://ash.confex.com/ash/2021/webprogram/Paper147386.html