Genome-wide study identifies novel genes associated with bone toxicities in children with acute lymphoblastic leukaemia.

Bone toxicities are common among paediatric patients treated for acute lymphoblastic leukaemia (ALL) with potentially major negative impact on patients' quality of life. To identify the underlying genetic contributors, we conducted a genome-wide association study (GWAS) and a transcriptome-wide association study (TWAS) in 260 patients of European-descent from the DFCI 05-001 ALL trial, with validation in 101 patients of European-descent from the DFCI 11-001 ALL trial. We identified a significant association between rs844882 on chromosome 20 and bone toxicities in the DFCI 05-001 trial (p = 1.7 × 10-8). In DFCI 11-001 trial, we observed a consistent trend of this variant with fracture. The variant was an eQTL for two nearby genes, CD93 and THBD. In TWAS, genetically predicted ACAD9 expression was associated with an increased risk of bone toxicities, which was confirmed by meta-analysis of the two cohorts (meta-p = 2.4 × 10-6). In addition, a polygenic risk score of heel quantitative ultrasound speed of sound was associated with fracture risk in both cohorts (meta-p = 2.3 × 10-3). Our findings highlight the genetic influence on treatment-related bone toxicities in this patient population. The genes we identified in our study provide new biological insights into the development of bone adverse events related to ALL treatment.

When transfusion causes a splitting headache: A case report and rapid review of transfusion-associated reversible cerebral vasoconstriction syndrome.

Reversible cerebral vasoconstriction syndrome (RCVS) is a rare and understudied transfusion reaction most commonly seen in adult females after correction of chronic, severe anemia. Transfusion-associated RCVS (TA-RCVS) typically presents with thunderclap headaches and one or more systemic (hypertension, nausea/vomiting) or neurologic (seizure, stroke, visual changes) symptoms within a week after red blood cell transfusion. Treatment of RCVS is based on blood pressure control; a recent study suggested that early use of nimodipine could shorten the disease course.

Time to diagnosis among young patients with cancer.

BACKGROUND: Sociodemographic and clinical factors associated with diagnostic delays in pediatric, adolescent, and young adult cancers are poorly understood. METHODS: Using the Optum Labs Data Warehouse's de-identified claims data for commercial health plan enrollees, we identified children (0-14 years) and adolescents/young adults (AYAs) (15-39 years) diagnosed with one of 10 common cancers from 2001 to 2017, who were continuously enrolled for 6 months preceding diagnosis. Time to diagnosis was calculated as days between first medical encounter with possible cancer symptoms and cancer diagnosis date. Median times from first symptom to diagnosis were compared using Wilcoxon rank sum test. Multivariable unconditional logistic regression identified sociodemographic factors associated with longer time (>3 months) to cancer diagnosis (from symptom onset). RESULTS: Of 47,296 patients, 87% presented prior to diagnosis with symptoms. Patients with central nervous system (CNS) tumors were most likely to present with symptoms (93%), whereas patients with cervical cancer were least likely (70%). Symptoms varied by malignancy. Of patients with symptoms, thyroid (105 days [range: 50-154]) and cervical (104 days [range: 41-151]) cancer had the longest median time to diagnosis. Females and patients at either end of the age spectrum were more likely to experience diagnosis delays of more than 3 months. CONCLUSION: In a commercially insured population, time to diagnosis varies by cancer type, age, and sex. Further work is needed to understand the patient, provider, and health system-level factors contributing to time from symptom onset to diagnosis, specifically in the very young children and the young adult patient population going forward.

Multilevel challenges to equitable inclusion of children in trials when parents use languages other than English: A qualitative report from Children's Oncology Group's Diversity and Health Disparities Committee Language Equity Working Group.

BACKGROUND: Increasing representation in clinical trials is a priority for the National Cancer Institute and Children's Oncology Group (COG). Our survey of COG-affiliated institutions revealed that many sites have insufficient processes and resources to enroll children whose parents use languages other than English (LOE). We describe reported barriers and facilitators to enrolling children in clinical trials when parents use LOE and propose opportunities for improvement. PROCEDURES: We sent a 20-item survey to COG-affiliated institutions. Five items allowed respondents to expand on replies to questions about (a) local institutional review board (IRB) requirements regarding translation of consent documents, (b) contributors to provider discomfort consenting parents who use LOE, (c) available language services and resources, and (d) barriers to enrolling children whose parents use LOE or offer ideas about approaches to improvements. Two pairs of researchers independently coded free-text responses and compared results for concordance. RESULTS: A total of 139 (N = 230; 60%) institutions returned the survey. Respondents were mainly physician principal investigators (n = 79/139; 57%) at the United States sites (n = 118/139; 85%) serving less than 100 newly diagnosed children per year (n = 99/139, 71%). They described challenges at multiple levels. Proposed approaches to improvements included centralized provision of translated materials and video educational materials in various languages, and collaborating with IRBs on regulatory processes that protect families and facilitate equitable clinical trial access. CONCLUSIONS: Clinical trial consortia, such as COG, face challenges in enrolling representative samples. Further research is required to design and implement multilevel interventions to ensure equitable access for all, regardless of language used, and mitigate disparate research participation.

Supplemental Nutrition Assistance Program participation gaps within a pediatric leukemia clinical trial cohort.

Poverty-exposed children with cancer are more likely to experience adverse outcomes. Supplemental Nutrition Assistance Program (SNAP) benefits improve food insecurity and child health outcomes, and could be used to mitigate disparities. We conducted a secondary analysis of parent-reported data collected in a frontline pediatric leukemia trial (NCT03020030) to assess SNAP eligibility (proxied by other means-tested program participation) and participation. At diagnosis, 105/287 families (37%) were SNAP-eligible, of whom 53 (50%) were SNAP participants. At 6 months, 104/257 families (41%) were SNAP-eligible, and 59 (57%) were SNAP participants. Interventions to increase benefits participation during childhood cancer treatment represent an immediate opportunity to reduce disparities.

Classic Hodgkin lymphoma.

Classic Hodgkin lymphoma (HL) is rare disease, with an incidence of approximately 85,000 patients globally per year and a predilection for adolescents and young adults (ages 15-39). Since the introduction of combination chemotherapy in the 1960's and radiation dating back to the early 1900's, therapeutic options and by extension, clinical outcomes have improved dramatically with 5-year overall survival (OS) approaching 90% today. [1](#ref-0001) Advances in understanding HL biology have additionally facilitated development of targeted agents and immunotherapy which have further improved short and long-term outcomes. Despite continued improvements in up-front and salvage therapy, long-term survivors of HL experience several treatment-associated late toxicities, thus, along with efforts to improve therapeutic efficacy, efforts to reduce late effects remain a high-priority in the field.

Children's Oncology Group's 2023 blueprint for research: Hodgkin lymphoma.

The goal of therapy in pediatric Hodgkin lymphoma (HL) is to maximize overall survival while minimizing the morbidity of curative therapy. Key findings from recent Children's Oncology Group (COG) trials include: (i) superior event-free survival with the addition of brentuximab vedotin (Bv) in frontline regimens for high-risk disease, (ii) successful reduction in myeloablative regimens with demonstrated safety and efficacy of Bv and checkpoint inhibitor therapy in relapsed disease, and (ii) the potential to select a population that can be salvaged after relapse without receiving a stem cell transplant. The COG HL committee will lead a National cancer Institute National Clinical Trials Network phase 3 trial to evaluate the combination of Bv/nivolumab in early-stage disease. Ongoing advances in technology and blood biomarkers are increasing the ability to deliver biologically driven, personalized treatment for HL.

Children's Oncology Group's 2023 blueprint for research: Diversity and health disparities.

The Children's Oncology Group (COG) Diversity and Health Disparities Committee's (DHDC's) mission is to guarantee the highest standard of care for children and adolescents and young adults (AYA) with cancer regardless of ethnic, racial, gender, or socioeconomic background. We strive to identify and address issues of disparity within the existing scientific structure of COG and to support research across COG to improve survival by ensuring equitable access to COG-sponsored clinical trials. We are committed to advance COG-led research identifying mechanistic drivers of disparities and, concurrently, evaluating interventions to alleviate disparities in the COG trial setting. As trials identify the most promising therapies, diverse representation is critical to ensure that findings are relevant to everyone. Factors impacting clinical trial participation among vulnerable populations are complex, consisting of barriers at societal, systems, and individual levels. Recent efforts by investigators within DHDC demonstrated that trial-embedded collection of family-reported sociodemographic data and social determinants of health (SDoH) is feasible and acceptable in the context of COG. Diversity in the pediatric oncology workforce is essential and one potential approach to improving representation on clinical trials. To support and retain diverse oncology providers and researchers, a Minority Young Investigator Award (MYIA) was created to facilitate opportunities for graduating trainees and YIs with an interest in childhood cancer disparities research within COG. Although there are challenges to achieve the DHDC's priorities, only through collaboration and support for this work we will be able to elucidate mechanisms underlying inferior survival outcomes for historically marginalized children and AYA, and more importantly, implement interventional investigation to improve outcomes.

New persistent opioid use among adolescents and young adults with sarcoma.

BACKGROUND: Adolescents and young adults (AYA) with sarcoma experience both acute and chronic pain related to their disease and treatment. Studies in older adults have reported a high risk of persistent opioid use after cancer therapy among previously opioid-naive patients; however, few studies have evaluated posttreatment opioid use among AYAs. This article describes patterns of new persistent opioid use among AYAs in the year after treatment for sarcoma. METHODS: Opioid-naive patients who were 10 to 26 years old and diagnosed with sarcoma (2008-2016) were identified with the IBM Marketscan Database. Included subjects had an International Classification of Diseases code for sarcoma (ninth or tenth revision), received anticancer therapy (chemotherapy, surgery, and/or radiation) within 30 days of the first diagnosis code, and had continuous insurance coverage (commercial or Medicaid) for more than 12 months both before the diagnosis and after the last therapy. The primary outcome was new persistent opioid use, which was defined as at least 2 opioid prescriptions in the 12 months following treatment completion. Covariates included age, sex, insurance, tumor type, surgical procedure, mental health (MH) or substance use diagnoses before or during therapy, and concomitant lorazepam use. RESULTS: In total, 938 patients met the inclusion criteria; 521 (56%) were male, and 578 (62%) were younger than 18 years. In total, 727 (78%) had commercial insurance, and 273 (29%) had an MH diagnosis either before or during the treatment period. Of the total group, 464 (49%) used opioids during treatment only. Of those who used opioids during treatment, 135 (23%) received at least 2 prescriptions in the year after therapy. In a multivariable analysis, Medicaid versus commercial insurance (odds ratio [OR], 1.74; 95% confidence interval [CI], 1.15-2.64) and non-soft tissue sarcoma (OR for Ewing sarcoma, 3.23; 95% CI, 1.81-5.78; OR for osteosarcoma, 2.05; 95% CI, 1.36-3.09) conferred a higher likelihood of new persistent use. CONCLUSIONS: In this cohort of AYAs treated for sarcoma, 64% of the patients received opioid prescriptions during treatment, and 23% of these patients became new persistent users. Because of the risks associated with persistent opioid use, studies of novel pain management strategies along with age-appropriate education and anticipatory guidance are urgently needed. LAY SUMMARY: Using an insurance claims database, we conducted a study to determine the rate of new persistent opioid use among adolescents and young adults treated for sarcoma. We found that 64% of adolescents and young adults treated for sarcoma received opioid prescriptions during treatment, and 23% of these patients met the criteria for new persistent opioid use. These findings support the need for age-appropriate education and novel pain management strategies in this vulnerable population.

Feasibility of oncology clinical trial-embedded evaluation of social determinants of health.

Social determinants of health (SDoH) are associated with stark disparities in cancer outcomes, but systematic SDoH data collection is virtually absent from oncology clinical trials. Trial-based SDoH data are essential to ensure representation of marginalized populations, contextualize outcome disparities, and identify health-equity intervention opportunities. We report the feasibility of a pediatric oncology multicenter therapeutic trial-embedded SDoH investigation. Among 448 trial participants, 392 (87.5%) opted-in to the embedded SDoH study; 375 (95.7%) completed baseline surveys, with high longitudinal response rates (88.9-93.1%) over 24 months. Trial-embedded SDoH data collection is feasible and acceptable and must be consistently included within future oncology trials.

Initial cancer treatment and survival in children, adolescents, and young adults with Hodgkin lymphoma: A population-based study.

BACKGROUND: Hodgkin lymphoma (HL) is a treatable tumor affecting children, adolescents and young adults (AYAs; 15-39 years old). Population-based studies report worse survival for non-White children and AYAs but have limited data on individual therapeutic exposures. This study examined overall and HL-specific survival in a population-based cohort of patients while adjusting for sociodemographic factors and treatment. METHODS: Data for 4807 patients younger than 40 years with HL (2007-2017) were obtained from the California Cancer Registry. Individual treatment information was extracted from text fields; chemotherapy regimens were defined by standard approaches for pediatric and adult HL. Multivariable Cox models examined the influence of patient and treatment factors on survival. RESULTS: At a median follow-up of 4.4 years, 95% of the patients were alive. Chemotherapy differed by age, with 70% of 22- to 39-year-olds and 41% of <22-year-olds receiving doxorubicin, bleomycin, vinblastine, and dacarbazine (P < .001). In multivariable models, older patients (22-39 vs < 21 y; hazard ratio [HR], 1.53; 95% confidence interval [CI], 1.11-2.10), Black (vs White patients); HR, 1.90; 95% CI, 1.25-2.88), and Hispanic patients (HR, 1.45; 95% CI, 1.06-1.99) experienced worse survival; among those < 21 y, Black race was associated with a 3.3-fold increased risk of death (HR, 3.26; 95% CI, 1.43-7.42). CONCLUSIONS: In children and AYAs with HL, older age and non-White race/ethnicity predicted worse survival after adjustments for treatment data. Further work is needed to identify the biological and nonbiological factors driving disparities in these at-risk populations.

Improving Health Equity and Reducing Disparities in Pediatric and Adolescent/Young Adult Oncology: In Support of Clinical Practice Guidelines.

Despite extraordinary strides in cancer therapy over the past 30 years, racial/ethnic, socioeconomic, and age-related survival disparities persist. Hodgkin lymphoma offers an excellent paradigm to understand these disparities because successful approaches are well established in both the up-front and relapsed treatment settings. The following review, which accompanies the 2021 NCCN Guidelines for Pediatric Hodgkin Lymphoma, suggests that systemic inequities in cancer care disproportionately affect minority and low-income children, adolescents, and young adults, and directly contribute to observed disparities in cancer-related outcomes. It proposes that the first step toward reducing disparities is large-scale dissemination of guidelines, because equity is best achieved when treatment approaches are clear, comprehensive, and standardized across all clinical practice settings.

Identification of prognostic factors in childhood T-cell acute lymphoblastic leukemia: Results from DFCI ALL Consortium Protocols 05-001 and 11-001.

BACKGROUND/OBJECTIVES: While outcomes for pediatric T-cell acute lymphoblastic leukemia (T-ALL) are favorable, there are few widely accepted prognostic factors, limiting the ability to risk stratify therapy. DESIGN/METHODS: Dana-Farber Cancer Institute (DFCI) Protocols 05-001 and 11-001 enrolled pediatric patients with newly diagnosed B- or T-ALL from 2005 to 2011 and from 2012 to 2015, respectively. Protocol therapy was nearly identical for patients with T-ALL (N = 123), who were all initially assigned to the high-risk arm. End-induction minimal residual disease (MRD) was assessed by reverse transcription polymerase chain reaction (RT-PCR) or next-generation sequencing (NGS), but was not used to modify postinduction therapy. Early T-cell precursor (ETP) status was determined by flow cytometry. Cases with sufficient diagnostic DNA were retrospectively evaluated by targeted NGS of known genetic drivers of T-ALL, including Notch, PI3K, and Ras pathway genes. RESULTS: The 5-year event-free survival (EFS) and overall survival (OS) for patients with T-ALL was 81% (95% CI, 73-87%) and 90% (95% CI, 83-94%), respectively. ETP phenotype was associated with failure to achieve complete remission, but not with inferior OS. Low end-induction MRD (<10-4 ) was associated with superior disease-free survival (DFS). Pathogenic mutations of the PI3K pathway were mutually exclusive of ETP phenotype and were associated with inferior 5-year DFS and OS. CONCLUSIONS: Together, our findings demonstrate that ETP phenotype, end-induction MRD, and PI3K pathway mutation status are prognostically relevant in pediatric T-ALL and should be considered for risk classification in future trials. DFCI Protocols 05-001 and 11-001 are registered at www.clinicaltrials.gov as NCT00165087 and NCT01574274, respectively.

Severe Vincristine-related Neurotoxicity in 5 Patients With Pediatric Acute Lymphoblastic Leukemia Requiring Discontinuation of Vincristine: A Description of Long-term Outcome.

Vincristine, a key agent in the treatment of many pediatric malignancies, causes sensory, motor and autonomic neuropathy. We report the clinical courses of 5 patients who required cessation of vincristine after developing severe neurotoxicity during treatment for acute lymphoblastic leukemia. All 5 patients lost the ability to ambulate and 3 had additional severe neurotoxic side effects including vision loss and vocal cord dysfunction. Although prior literature reports poor outcomes for children in whom vincristine was discontinued during acute lymphoblastic leukemia therapy, all 5 patients described here achieved and have maintained complete continuous remission.

Race and socioeconomic status in pediatric allogeneic hematopoietic cell transplantation for nonmalignant conditions.

BACKGROUND: Survival disparities by race/ethnicity and socioeconomic status (SES) are observed in a wide range of pediatric treatment settings including oncology and solid organ transplantation. To date, few studies have examined the effects of race and SES on outcomes in pediatric allogeneic hematopoietic cell transplantation (HCT). We explored whether survival differed by race/ethnicity or SES in children receiving HCT for nonmalignant conditions at a single institution serving a diverse patient population. PROCEDURES: The Kaplan-Meier method was used to estimate overall survival (OS) with the log-rank test for between-group comparisons. Cox proportional hazards models were used to identify risk factors for OS, adjusting for treatment- and disease-related factors. RESULTS: Of 133 subjects, 0 to 21 years, 19% were non-Hispanic (NH) white, 34% were NH black, 40% were Hispanic, and 7% were Asian. Sixty-seven percent of the subjects had public insurance; 49% lived in neighborhoods with poverty rate ≥20%. Primary diagnoses included hemoglobinopathies (56%), bone marrow failure (22%), and other conditions (22%). Median follow-up was 5.8 years (range 0.1-14.5). Analysis revealed no difference in OS by race, insurance type, or neighborhood SES. CONCLUSIONS: Findings from this single-institution study suggest that in pediatric patients undergoing HCT for nonmalignant conditions, treatment at a tertiary care center with a multidisciplinary approach may mitigate drivers of disparities observed in other settings. Additional studies are now needed to further elucidate the complex interrelationships among race, SES, and clinical outcomes for children undergoing HCT.

Bone Marrow Harvest in Pediatric Sibling Donors: Role of Granulocyte Colony-Stimulating Factor Priming and CD34+ Cell Dose.

To ensure optimal clinical outcomes for patients while retaining adequate protection for donors, the National Marrow Donor Program developed guidelines specifying that up to 20 mL/kg of bone marrow can be harvested from donors. These guidelines, originally developed for unrelated adult donors, are followed in children as well. We studied the impact of granulocyte colony-stimulating factor (G-CSF) priming on the cellular composition of harvested bone marrow, sought to develop an algorithm to optimize bone marrow harvest volume from pediatric matched sibling donors, and studied the impact of CD34+ cell dose on clinical outcomes. We analyzed data from 92 bone marrow harvests and clinical outcomes for 69 sibling recipient-donor duos, The mean age of recipients was 9.85 ± 5.90 years, and that of donors was 11.85 ± 6.36 years. G-CSF priming was not associated with higher yield of CD34+ cells/µL. The median CD34+ cell count obtained from donors was 700 cells/µL (range, 400-1700 cells/µL) in donors age <6 years, 360 cells/µL (range, 100-1100 cells/µL) in donors age 6 to 12 years, and 300 cells/µL (range, 80-800 cells/µL) in donors age >12 years (P < .001). The number of CD34+ cells infused had no impact on traditional clinical outcomes; however, it was significantly related to graft-versus-host disease/relapse/rejection-free survival. Our investigation revealed that ultimately, a CD34+ cell count of approximately 3 to 5 × 106/kg was a threshold beyond which increasing CD34+ cell dose did not impact outcome. In this study, we addressed the broad question of whether harvesting up to 20 mL/kg of bone marrow from a child donor is truly necessary for optimal outcomes in every pediatric case.

Adolescent and young adult Hodgkin lymphoma: Raising the bar through collaborative science and multidisciplinary care.

Hodgkin lymphoma (HL) is one of the most common cancers in the adolescent and young adult (AYA) population (15-39 years). Despite continued improvements in HL outcomes, AYAs have not exhibited survival gains to the same extent as other age groups. At present, details about tumor biology, optimal therapeutic approaches, supportive care needs, and long-term toxicities in AYAs with HL remain understudied. Herein, we summarize the current state of the AYA population with HL, specifically focusing on how collaborations across the pediatric and medical oncology divide, coupled with multidisciplinary patient care, can further optimize outcomes for this group of patients.

An investigation of toxicities and survival in Hispanic children and adolescents with ALL: Results from the Dana-Farber Cancer Institute ALL Consortium protocol 05-001.

PURPOSE: This study compared the relative incidence of treatment-related toxicities and the event-free and overall survival between Hispanic and non-Hispanic children undergoing therapy for acute lymphoblastic leukemia (ALL) on Dana-Farber Cancer Institute ALL Consortium protocol 05-001. PATIENTS AND METHODS: Secondary analysis of prospectively collected data from a phase III multicenter study in children and adolescents of 1-18 years with previously untreated ALL. RESULTS: Between 2005 and 2011, 794 eligible patients enrolled on DFCI 05-001, 730 of whom were included in this analysis (19% [N = 150] Hispanic, 73% [N = 580] non-Hispanic). Hispanic patients were more likely to be ≥10 years of age (32% vs. 24%, P = 0.045) at diagnosis. Toxicity analyses revealed that Hispanic patients had significantly lower cumulative incidence of bone fracture (P < 0.001) and osteonecrosis (ON; P = 0.047). In multivariable risk regression, the risk of ON was significantly lower in Hispanic patients ≥10 years (HR 0.23; P = 0.006). Hispanic patients had significantly lower 5-year event-free survival (EFS) (79.4%; 95% CI: 71.6-85.2) and overall survival (OS) (89.2%; 95% CI: 82.7-93.4) than non-Hispanic patients (EFS: 87.5%; 95% CI: 84.5-90.0, P = 0.004; OS: 92.7%; 95% CI: 90.2-94.6, P = 0.006). Exploratory analyses revealed differences between Hispanic and non-Hispanic patients in the frequency of common variants in genes related to toxicity or ALL outcome. CONCLUSION: Hispanic children treated for ALL on DFCI 05-001 had fewer bone-related toxicities and inferior survival than non-Hispanic patients. While disease biology is one explanatory variable for outcome disparities, these findings suggest that biologic and non-biologic mechanisms affecting drug delivery and exposure in this population may be important contributing factors as well.

Risk Factors for Subtherapeutic Tacrolimus Levels after Conversion from Continuous Intravenous Infusion to Oral in Children after Allogeneic Hematopoietic Cell Transplantation.

Tacrolimus (FK506) is a calcineurin inhibitor and is an essential component of many immunosuppressive regimens. The oral bioavailability of tacrolimus may be affected by many factors, including patient age and gender, as well as by drug-drug interactions or genetic polymorphisms in drug metabolism. The dosing recommendations for pediatric allogeneic hematopoietic cell transplantation (alloHCT) recipients have been derived from tacrolimus use in adult solid-organ transplantation patients. Data describing the impact of conversion of i.v. tacrolimus to oral on the incidence of acute graft-versus-host disease (aGVHD) are limited in children after alloHCT. In this study, we describe the incidence of grades II to IV aGVHD after conversion from i.v. tacrolimus to oral tacrolimus and study the clinical factors associated with delayed achievement of therapeutic blood levels. In this retrospective analysis, 68 pediatric patients (median age, 6.7 years; range, .25 to 22 years), underwent alloHCT for malignant and nonmalignant diseases and received tacrolimus and mycophenolate mofetil for aGVHD prophylaxis. Among all patients, the median number of days to achieve therapeutic tacrolimus trough concentration (10 ng/mL to 20 ng/mL) was 7 days (range, 0 to 37 days). Twenty-two patients developed grades II to IV aGVHD and the cumulative incidence of grades II to IV aGVHD in all patients was 32.4% (standard error, .06). On multivariate analysis ethnicity (white versus others: odds ratio [OR], -4.5; 95% confidence interval [95% CI], 1.091 to 18.91; P = .038) and ≥ 10 days of subtherapeutic tacrolimus levels in first 30 days on i.v. (OR, -3.8; 95% CI, 1.276 to 11.43; P = .017) were significantly associated with delay in achieving therapeutic tacrolimus trough concentration. The impact of race/ethnicity on therapeutic tacrolimus trough concentration in pediatric alloHCT recipients should be further studied prospectively so that individualized dosing plans can be developed.