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Abstract: The association between antimetabolite dose intensity (DI) and adverse events among children receiving maintenance therapy for acute lymphoblastic leukemia (ALL) remains unclear, especially in the context of antimetabolite adherence. Using Children's Oncology Group AALL03N1 data, we examined the association between high DI during the first 4 study months and (i) treatment-related toxicities during the subsequent 2 study months; and (ii) relapse risk. Patients were classified into a high DI phenotype (either 6-mercaptopurine [6-MP] or methotrexate [MTX] DI ≥110% during the first 4 study months, or 6-MPDI or MTXDI 100%-110% at study enrollment and ≥25% increase over the 4 study months) and normal DI phenotype (all others). Only patients with wild-type TPMT and NUDT15 were included. 6-MP adherence data were available for 63.7% of study participants and used to stratify as adherent (median adherence ≥85%) and nonadherent (median adherence <85%) participants. Multivariable analyses were adjusted for sociodemographic and clinical prognosticators. Of the 644 patients, 29.3% were exposed to high DI. High DI was associated with a 2.1-fold greater odds of hematologic toxicity (95% confidence interval [CI] = 1.4-3.1; reference: normal DI) in the entire cohort and 2.9-fold higher among adherers (95% CI = 1.6-5.1); odds were comparable among nonadherers (2.1-fold; 95% CI = 0.4-10.1). Although high DI was not associated with relapse in the entire cohort (adjusted hazard ratio [aHR] = 1.4; 95% CI = 0.8-2.4), it was associated with a greater hazard of relapse among adherent participants (aHR = 2.4; 95% CI = 1.0-5.5) but not among nonadherent participants (aHR = 0.9; 95% CI = 0.2-3.8). Dose escalation above protocol doses during maintenance therapy for ALL should be done cautiously after assessing adherence to prescribed therapy., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

The association between individual-level poverty and relapse in children receiving maintenance treatment for acute lymphoblastic leukemia (ALL) remains unclear. In a secondary analysis of COG-AALL03N1, we used data from US Census Bureau to categorize patients living below year-specific federal poverty thresholds, calculated using self-reported annual household income and size of household. Participants with federal poverty thresholds above 120% of their yearly household income were categorized as living in extreme poverty. Hazard of relapse was estimated using multivariable proportional subdistributional hazards regression for patients living in extreme poverty while receiving ALL maintenance therapy after adjusting for relevant predictors. Among 592 patients in this analysis, 12.3% of the patients were living in extreme poverty. After a median follow-up of 7.9 years, the cumulative incidence of relapse at 3 years from study enrollment among those living in extreme poverty was significantly higher (14.3%) than those not living in extreme poverty (7.6%). Multivariable analysis demonstrated that children living in extreme poverty had a 1.95-fold greater hazard of relapse than those not living in extreme poverty; this association was mitigated after the inclusion of race/ethnicity in the model, likely because of collinearity between race/ethnicity and poverty. A greater proportion of children living in extreme poverty were nonadherent to mercaptopurine (57.1% vs 40.9%); however, poor adherence did not completely explain the association between poverty and relapse risk. Future studies need to understand the mechanisms underlying the association between extreme poverty and relapse risk. This trial was registered at www.clinicaltrials.gov as #NCT00268528., (© 2023 by The American Society of Hematology.)

Adequate exposure to oral 6-mercaptopurine (6MP) during maintenance therapy for childhood acute lymphoblastic leukemia (ALL) is critical for sustaining durable remissions; accuracy of self-reported 6MP intake is unknown. We aimed to directly compare self-report to electronic monitoring (Medication Event Monitoring System [MEMS]) and identify predictors of overreporting in a cohort of 416 children with ALL in first remission over 4 study months (1344 patient-months for the cohort) during maintenance therapy. Patients were classified as "perfect reporters" (self-report agreed with MEMS), "overreporters" (self-report was higher than MEMS by ≥5 days/month for ≥50% of study months), and "others" (not meeting criteria for perfect reporter or overreporter). Multivariable logistic regression examined sociodemographic and clinical characteristics, 6MP dose intensity, TPMT genotype, thioguanine nucleotide levels, and 6MP nonadherence (MEMS-based adherence <95%) associated with the overreporter phenotype; generalized estimating equations compared 6MP intake by self-report and MEMS. Self-reported 6MP intake exceeded MEMS at least some of the time in 84% of patients. Fifty patients (12%) were classified as perfect reporters, 98 (23.6%) as overreporters, 2 (0.5%) as underreporters, and 266 (63.9%) as others. In multivariable analysis, the following variables were associated with the overreporter phenotype: non-white race: Hispanic, odds ratio (OR), 2.4, P = .02; Asian, OR, 3.1, P = .02; African American, P < .001; paternal education less than college (OR, 1.4, P = .05); and 6MP nonadherence (OR, 9.4, P < .001). Self-report of 6MP intake in childhood ALL overestimates true intake, particularly in nonadherent patients, and should be used with caution., (© 2017 by The American Society of Hematology.)

Durable remissions in children with acute lymphoblastic leukemia (ALL) require a 2-year maintenance phase that includes daily oral 6-mercaptopurine (6MP). Adherence to oral 6MP among Asian-American and African-American children with ALL is unknown. We enrolled 298 children with ALL (71 Asian Americans, 68 African Americans, and 159 non-Hispanic whites) receiving oral 6MP for the maintenance phase. Adherence was measured electronically for 39 803 person-days. Adherence declined from 95.0% (month 1) to 91.8% (month 5, P < .0001). Adherence rates were significantly (P < .0001) lower in Asian Americans (90.0% ± 4.9%) and African Americans (87.1% ± 4.4%), as compared with non-Hispanic whites (95.2% ± 1.3%). Race-specific sociodemographic characteristics helped explain poor adherence (African Americans: low maternal education [less than a college degree: 78.9%, vs at least college degree: 94.6%; P < .0001]; Asian Americans: low-income households [<$50 000: 84.5%, vs ≥$50 000: 96.7%; P = .04]; households without mothers as full-time caregivers [85.6%] vs households with mothers as full-time caregivers [97.2%; P = .05]). Adherence rate below 90% was associated with increased relapse risk (hazard ratio, 3.9; P = .01). Using an adherence rate <90% to define nonadherence, 20.5% of the participants were nonadherers. We identify race-specific determinants of adherence, and define a clinically relevant level of adherence needed to minimize relapse risk in a multiracial cohort of children with ALL. This trial was registered at www.clinicaltrials.gov as #NCT00268528., (© 2014 by The American Society of Hematology.)