According to recent findings from a study presented at the American Association for Cancer Research Annual Meeting, among pediatric patients diagnosed with ALL, pediatric patients of Latino descent without minimal residual disease (MRD) had a greater probability of relapse than pediatric patients who are non-Latino Caucasian. The researchers indicated that ALL is the most common form of cancer diagnosed in pediatric patients; however, due to advancement in therapy, the 5-year survival rate of pediatric patients with ALL is about 90%.

The lead author of the study, Philip Lupo, PhD, professor of pediatrics at Baylor College of Medicine, director of the Epidemiology and Population Sciences Program at Texas Children's Cancer and Hematology Center, and member of the Dan L. Duncan Comprehensive Cancer Center at Baylor, stated, "Approximately 15% of children with ALL will experience a relapse."

Dr. Lupo also stated, "Outcomes after relapse are much worse, with only 35% of children surviving after disease recurrence. Additionally, poor outcomes are more common among Latinos, who are also more likely to develop ALL compared to non-Latino whites."

The research indicated that detection of MRD in the bone marrow after the first month of treatment is the strongest prognostic factor for ALL relapse. However, about half of all relapses occur in children who are MRD-negative. In this study, Dr. Lupo, et al, sought to investigate correlations between MRD status and Latino ethnicity and to characterize other factors associated with relapse.

Additionally, the researchers examined data from the Reducing Ethnic Disparities in Acute Leukemia (REDIAL) Consortium, which includes patients diagnosed with ALL at six major pediatric cancer centers in the southwestern United States. The study included 1,620 children diagnosed with ALL between 2004 and 2018 with an average age at diagnosis of 5 years. The majority were Latino (60.1%) and male (56.9 %). In all, 382 (23.5 %) of the subjects were MRD-positive. Of these, 73 (19.1 %) experienced a relapse, compared with 136 of 1,238 (11.0 %) MRD-negative patients.

Among the MRD-positive patients, Latinos were less likely to have a relapse compared to non-Latino whites; however, Latinos who were MRD-negative were about 65% more likely to have a relapse than non-Latino Caucasians. The authors concluded that their findings suggested that MRD status may not be as robust a prognostic factor in predicting the risk of relapse in Latino children with ALL compared with non-Latino Caucasians.

Other factors identified in the study included the following: patients who had been diagnosed with ALL after 15 years of age were approximately twice as likely to relapse than those between ages 1 and 5 years, and patients enrolled in a therapeutic clinical trial for ALL were less likely to have a relapse.

Dr. Lupo stated, "The study emphasizes the significance of examining the roots of cancer health disparities. We were surprised that Latinos who were MRD-negative were more likely to experience ALL relapse compared to non-Latino whites. This highlights the need to identify factors that contribute to relapse among Latinos so that we can achieve better outcomes for children of all racial and ethnic backgrounds."

Moreover, Dr. Lupo said that while MRD should still be considered an important prognostic factor in ALL, this study indicates that it may not have the same prognostic implication across all populations. The REDIAL Consortium is also continuing to research other ethnic disparities in ALL and acute myeloid leukemia. They are examining why Latinos are more likely to develop leukemia and are also examining the frequency and risk factors that may augment the development of treatment-related toxicities.

Dr. Lupo indicated that one drawback of the study is that the researchers did not have complete information about all factors that could have influenced relapse risk. He added that future research will incorporate other important factors into predictive models of ALL outcomes, including biological features inherent to the leukemia, inherited genetic factors, and social determinants of health.

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