Asparaginase Induced Liver Enzyme Elevation Is More Prevalent in Hispanics Children with ALL and in Patients with SOD2 rs4880 CC Genotype

Background: Asparaginase is an integral component of treatment for pediatric patients with acute lymphoblastic leukemia (ALL). Hepatotoxicity secondary to asparaginase-based treatment is one of the most common treatment-related toxicities in ALL therapy. Hispanic children are at higher risk of ALL and ALL treatment related toxicities compared with other ethnicities. The rs4880 variant in the SOD2 gene, a critical mitochondrial enzyme that protects cells against oxidative stress, was previously found to be associated with increased incidence of hepatotoxicity following asparaginase treatment in an adult ALL cohort of largely European ancestry. Whether this association is also present in pediatric patients with ALL and in Hispanics remains unknown. Importantly, the risk genotype (CC) of rs4880 is more frequent among Hispanics. Here we aim to investigate the prevalence of hepatotoxicity and risk genotype among pediatric patients with ALL particularly of Hispanics ancestry. Method: Blood samples, demographic and clinical data were obtained from 143 pediatric patients treated for ALL between 29 January 2015 and 24 January 2020 at Children's Hospital Los Angeles. We genotyped DNA samples isolated from the patient's blood for the rs4880 variant of SOD2 using TaqMan Allelic Discrimination Assay. Liver enzyme data, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin levels for each subject following multiple visits before and post asparaginase-based treatment were obtained. Hepatotoxicity is defined as grade 3/4 of both AST and ALT, grade 4 of either AST or ALT, or grade 3/4 of bilirubin. We performed Cox Proportional Hazards models to evaluate the predictive factors of hepatotoxicity overtime. Results: Among the 143 patients, 13 (9.09%) patients had grade > 3 elevated bilirubin levels, and 3 (2.1%) and 55 (38.46%) patients had grade > 4 and > 3 elevated AST levels respectively, and 19 (13.29%) and 109 (76.22%) had grade > 4 and > 3 elevated ALT levels respectively. Hepatotoxicity was observed in 60 (41.96%) of patients. After dichotomizing patients based on ethnicity (Hispanic and non-Hispanic), we found that BMI was significantly higher in Hispanics than non-Hispanic patients (mean BMI: 21.57 vs 18.64, p=0.002). While mean baseline levels of liver enzymes were not significantly different between Hispanic and non-Hispanic patients (bilirubin:0.69 vs 0.64, ALT: 156.06 vs 124.75, and AST: 99.98 vs 82.38), post-treatment levels were significantly higher in hispanics (ALT: 138.105 vs. 101.45, p=0.0005; AST: 84.131 vs. 64.045, p=0.0023). After chemotherapy, grade 3 or 4 elevated bilirubin was found in 11 (12.36%) of 89 Hispanic patients and only in 2 (3.7%) of 54 non-Hispanic patients. Also, there was a statistically significant difference in the frequency of elevated ALT level grade > 4 and grade > 3 between Hispanic and non-Hispanic patients (grade > 4: 17 (19.10%) vs 2 (3.70), p= 0.01; grade > 3: 74 (83.15%) vs 35 (64.8%), p=0.01). Consequently, Hepatotoxicity was more frequent among Hispanic patients than non-Hispanic, 47.19% vs 33.33%; p=0.10, respectively. We also compared hepatotoxicity parameters according to the patient's rs4880 genotypes. Among patients with the SOD2 rs4880 CC genotype 3 (6.32%) had grade > 4 and 23 (50%) had grade > 3 elevated AST compared with 0 (0%) and 21 (30%) among the CT and 0 (0%) and 11 (40.74%) among the TT genotype patients (CC vs. CT and TT; AST grade > 4: p=0.13; grade > 3 : p=0.05). In addition, elevated bilirubin grade > 3 was found more frequently in patients with the SOD2 rs4880 CC genotype (15.22%) compared with those with the CT (5.71%) and TT (7.41%) genotypes. Furthermore, post-treatment bilirubin, ALT and AST median levels were significantly higher in patients with the CC genotype than in patients with CT or TT genotypes (bilirubin: 0.8275 vs. 0.6, p=0.0007; ALT: 142.555 vs. 106.038, p=0.0089; AST: 85.399 vs. 67.888, p= 0.0302). In a multivariate Cox analysis, that included ethnicity, age, gender, BMI and genotype, we identified Ethnicity (Hispanic) as the only significant predictor of hepatotoxicity (hazard ratio [HR] = 1.862, 95% confidence interval [95% CI] 1.-3.465, p=0.0499). Conclusion: Overall, these findings suggested that hepatotoxicity is highly prevalent among Hispanic pediatric patients with ALL, especially those with CC genotype of rs4880.