In a prospective study, Hispanic pediatric patients with acute lymphoblastic leukemia (ALL) had a risk of methotrexate-induced neurotoxicity that was more than twice the risk observed in non-Hispanic white patients.
However, there was no significant difference in methotrexate neurotoxicity between non-Hispanic black patients and non-Hispanic white patients.
There were no cases of neurotoxicity among patients of other races/ethnicities.
Michael E. Scheurer, PhD, of Baylor College of Medicine in Houston, Texas, and his colleagues conducted this study and detailed the results in Clinical Cancer Research.
The study included 280 patients with newly diagnosed ALL. Most patients (85.7%) had B-ALL, 10.7% had T-ALL, and 3.6% had lymphoblastic lymphoma.
Nearly half of the patients (48.2%) were Hispanic, 36.2% were non-Hispanic white, 8.3% were non-Hispanic black, and 7.3% were non-Hispanic “other.”
The patients, who had a mean age of 8.4 years at diagnosis, were treated with modern ALL protocols and were followed from diagnosis to the start of maintenance/continuation therapy.
Methotrexate neurotoxicity was seen in 39 patients at the time of the analysis. Of those patients, 29 (74.4%) were Hispanic.
Compared with non-Hispanic whites, Hispanics had a high risk of methotrexate neurotoxicity, even after the researchers accounted for age, sex, ALL risk stratification, and other factors. The adjusted hazard ratio (HR) was 2.43 (P=0.036).
“We had observed that our Hispanic patients tended to experience neurotoxicity more often than other groups, but we were surprised to see the magnitude of the difference,” Dr. Scheurer said.
There was no significant difference in methotrexate neurotoxicity between non-Hispanic black patients and non-Hispanic white patients. The adjusted HR for non-Hispanic black patients was 1.23 (P=0.80).
Patients in the “other” racial/ethnic group did not experience any neurotoxic events.
All nine patients who experienced a second neurotoxic event were Hispanic.
Patients who had neurotoxicity received an average of 2.25 fewer doses of intrathecal methotrexate (P<0.01) and 1.81 fewer doses of intravenous methotrexate (P=0.084) than patients without neurotoxicity.
About three-quarters (74.4%) of patients experiencing methotrexate neurotoxicity received leucovorin rescue, according to the investigators, who noted that leucovorin may interact with methotrexate and reduce its efficacy.
Relapse occurred in 15.4% (6/39) of patients with neurotoxicity and 2.1% (13/241) of patients with no neurotoxicity (P=0.0038).
The investigators said these findings add to the growing body of evidence that Hispanics and other minority pediatric patients with ALL experience “significant disparities” in treatment outcomes.
It remains unclear why Hispanic patients would have a higher risk of methotrexate neurotoxicity, and that must be explored in future studies, the investigators said.
The team is currently investigating whether biomarkers could be used to identify patients at risk of methotrexate neurotoxicity.
“Biomarkers may someday allow us to identify patients upfront, before even beginning therapy, who might be at risk for such outcomes,” Dr. Scheurer said. “If we can identify these at-risk patients, we can potentially employ strategies to either fully prevent or mitigate these toxicities.”
This research was supported by the National Institutes of Health and Reducing Ethnic Disparities in Acute Leukemia (REDIAL) Consortium, a St. Baldrick’s Foundation Consortium Research Grant. The researchers said they had no potential conflicts of interest.