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Novel drugs are needed to increase treatment response in children with high-risk T-cell acute lymphoblastic leukemia (T-ALL). Following up on our previous report on the activation of the MAP2K7-JNK pathway in pediatric T-ALL, here we demonstrate that OTSSP167, recently shown to inhibit MAP2K7, has antileukemic capacity in T-ALL. OTSSP167 exhibited dose-dependent cytotoxicity against a panel of T-ALL cell lines with IC50 in the nanomolar range (10-50 nM). OTSSP167 induces apoptosis and cell cycle arrest in T-ALL cell lines, associated at least partially with the inhibition of MAP2K7 kinase activity and lower activation of its downstream substrate, JNK. Other leukemic T-cell survival pathways, such as mTOR and NOTCH1 were also inhibited. Daily intraperitoneal administration of 10 mg/kg OTSSP167 was well tolerated, with mice showing no hematological toxicity, and effective at reducing the expansion of human T-ALL cells in a cell-based xenograft model. The same dosage of OTSSP167 efficiently controlled the leukemia burden in the blood, bone marrow, and spleen of 3 patient-derived xenografts, which resulted in prolonged survival. OTSSP167 exhibited synergistic interactions when combined with dexamethasone, L-asparaginase, vincristine, and etoposide. Our findings reveal novel antileukemic properties of OTSSP167 in T-ALL and support the use of OTSSP167 as an adjuvant drug to increase treatment response and reduce relapses in pediatric T-ALL.

S1: supplementary table - PDF file 61K, S1: supp. table

Purpose: Although modern cure rates for childhood acute lymphoblastic leukemia (ALL) exceed 80%, the outlook remains poor in patients with high-risk disease and those who relapse, especially when allogeneic hematopoietic stem cell transplantation is not feasible. Strategies to improve outcome and prevent relapse are therefore required. Immunotherapy with antigen-specific T cells can have antileukemic activity without the toxicities seen with intensive chemotherapy, and therefore represents an attractive strategy to improve the outcome of high-risk patients with ALL. We explored the feasibility of generating tumor antigen-specific T cells ex vivo from the peripheral blood of 50 patients with ALL [26 National Cancer Institute (NCI) high-risk and 24 standard-risk] receiving maintenance therapy.Experimental Design: Peripheral blood mononuclear cells were stimulated with autologous dendritic cells pulsed with complete peptide libraries of WT1, Survivin, MAGE-A3, and PRAME, antigens frequently expressed on ALL blasts.Results: T-cell lines were successfully expanded from all patients, despite low lymphocyte counts and irrespective of NCI risk group. Antigen-specificity was observed in more than 50% of patients after the initial stimulation and increased to more than 90% after three stimulations as assessed in IFN-γ-enzyme-linked immunospot (ELISpot) and 51Cr-release assays. Moreover, tumor-specific responses were observed by reduction of autologous leukemia blasts in short- and long-term coculture experiments.Conclusion: This study supports the use of immunotherapy with adoptively transferred autologous tumor antigen-specific T cells to prevent relapse and improve the prognosis of patients with high-risk ALL. Clin Cancer Res; 19(18); 5079–91. ©2013 AACR.

Supplementary data: Figures S2-S8 - PDF file 312K, Supplementary Figure S2: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 963) Supplementary Figure S3: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 996) Supplementary Figure S4: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 1024) Supplementary Figure S5: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 1025)Supplementary Figure S6: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 1292) Supplementary Figure S7: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 1331) Supplementary Figure S8: Co-culture experiments of TAA-specific T cells with autologous blasts (Patient ID # 1339)

Trisomy 21, the genetic cause of Down syndrome (DS), is the most common congenital chromosomal anomaly. It is associated with a 20-fold increased risk of acute lymphoblastic leukemia (ALL) during childhood and results in distinctive leukemia biology. To comprehensively define the genomic landscape of DS-ALL, we performed whole genome sequencing and whole-transcriptome sequencing (RNA-Seq) on 295 cases. Our integrated genomic analyses identified 15 molecular subtypes of DS-ALL, with marked enrichment of CRLF2-r, IGH::IGF2BP1, and C/EBP altered (C/EBPalt) subtypes compared to 2257 non-DS-ALL cases. We observed abnormal activation of the CEBPD, CEBPA, and CEBPE genes in 10.5% of DS-ALL cases, via a variety of genomic mechanisms, including chromosomal rearrangements and noncoding mutations leading to enhancer hijacking. 42.3% of C/EBP-activated DS-ALL also have concomitant FLT3 point mutation or indel, relative to 4.1% in other subtypes (P=7.2×10-6). CEBPD overexpression enhanced the differentiation of mouse hematopoietic progenitor cells into pro-B cells in vitro, particularly in a DS genetic background. Notably, RAG-mediated somatic genomic abnormalities were common in DS-ALL, accounting for a median of 27.5% of structural alterations, compared to 7.7% in non-DS-ALL (P=2.1×10-12). Unsupervised hierarchical clustering analyses of CRLF2-rearranged DS-ALL identified substantial heterogeneity within this group, with the BCR::ABL1-like subset linked to an inferior event-free survival (hazard ratio=5.27, P=9.3×10-8), even after adjusting for known clinical risk factors (hazard ratio=4.32; P=0.0020). These results provide important insights into the biology of DS-ALL and point to opportunities for targeted therapy and treatment individualization.

Racial and ethnic inequities in survival persist for children with acute lymphoblastic leukemia (ALL). In the US, there are strong associations between SES, race/ethnicity, and place of residence. This is evidenced by ethnic enclaves: neighborhoods with high concentrations of ethnic residents, immigrants, and language isolation. The Latinx enclave index (LEI) can be used to investigate how residence in a Latinx enclave is associated with health outcomes. We studied the association between LEI score and minimal residual disease (MRD) in 142 pediatric ALL patients treated at Texas Children’s Hospital. LEI score was associated with end-induction MRD positivity (OR per unit increase 1.63, CI 1.12–2.46). There was also a significant trend toward increased odds of MRD positivity among children living in areas with the highest enclave index scores. MRD positivity at end of induction is associated with higher incidence of relapse and lower overall survival among children with ALL; future studies are needed to elucidate the exact causes of these findings and to improve ALL outcomes among children residing within Latinx enclaves. Supplemental data for this article is available online at https://doi.org/10.1080/08880018.2022.2047850

Children with Down syndrome (DS) are at a significantly higher risk of developing acute myeloid leukemia, also termed myeloid leukemia associated with DS (ML-DS). In contrast to the highly favorable prognosis of primary ML-DS, the limited data that are available for children who relapse or who have refractory ML-DS (r/r ML-DS) suggest a dismal prognosis. There are few clinical trials and no standardized treatment approach for this population. We conducted a retrospective analysis of international study groups and pediatric oncology centers and identified 62 patients who received treatment with curative intent for r/r ML-DS between 2000-2021. Median time from diagnosis to relapse was 6.8 (range 1.1 - 45.5) months. Three-year event-free (EFS) and overall survival (OS) were 20.9±5.3% and 22.1±5.4%, respectively. Survival was associated with receipt of hematopoietic stem cell transplantation (HSCT) (HR 0.28), duration of first complete remission (CR1) (HR 0.31 for > 12 months) and attainment of remission after relapse (HR 4.03). Patients who achieved CR prior to HSCT, had an improved OS and EFS of 56.0±11.8% and 50.5±11.9% respectively, compared to those who underwent HSCT without CR (3-year OS and EFS of 10.0±9.5%). Treatment failure after HSCT was predominantly due to disease recurrence (52%) followed by treatment related mortality (10%). The prognosis of r/r ML-DS remains dismal even in the current treatment period and serve as a reference point for current prognostication and future interventional studies. Clinical trials aimed at improving the survival of patients with r/r ML-DS are needed.

To determine the prognostic significance of central nervous system (CNS) leukemic involvement in newly diagnosed T-cell acute lymphoblastic leukemia (T-ALL), outcomes on consecutive, phase 3 Children’s Oncology Group clinical trials were examined. AALL0434 and AALL1231 tested efficacy of novel agents within augmented-Berlin-Frankfurt-Münster (aBFM) therapy. In addition to testing study-specific chemotherapy through randomization, the AALL0434 regimen delivered cranial radiation therapy (CRT) to most participants (90.8%), whereas AALL1231 intensified chemotherapy to eliminate CRT in 88.2% of participants. In an analysis of 2164 patients with T-ALL (AALL0434, 1550; AALL1231, 614), 1564 had CNS-1 (72.3%), 441 CNS-2 (20.4%), and 159 CNS-3 (7.3%). The 4-year event-free-survival (EFS) was similar for CNS-1 (85.1% ± 1.0%) and CNS-2 (83.2% ± 2.0%), but lower for CNS-3 (71.8% ± 4.0%; P = .0004). Patients with CNS-1 and CNS-2 had similar 4-year overall survival (OS) (90.1% ± 0.8% and 90.5% ± 1.5%, respectively), with OS for CNS-3 being 82.7% ± 3.4% (P = .005). Despite therapeutic differences, outcomes for CNS-1 and CNS-2 were similar regardless of CRT, intensified corticosteroids, or novel agents. Except for significantly superior outcomes with nelarabine on AALL0434 (4-year disease-free survival, 93.1% ± 5.2%), EFS/OS was inferior with CNS-3 status, all of whom received CRT. Combined analyses of >2000 patients with T-ALL identified that CNS-1 and CNS-2 status at diagnosis had similar outcomes. Unlike B-ALL, CNS-2 status in T-ALL does not impact outcome with aBFM therapy, without additional intrathecal therapy, with or without CRT. Although nelarabine improved outcomes for those with CNS-3 status, novel approaches are needed. These trials were registered at www.clinicaltrials.gov as #NCT00408005 (AALL0434) and #NCT02112916 (AALL1231).

Infections cause substantial morbidity for children with acute lymphoblastic leukemia (ALL). Therefore, accurate characterization of infectious adverse events (AEs) reported on clinical trials is imperative to defining, comparing, and managing safety and toxicity. Here, we describe key processes implemented to improve reporting of infectious AEs on two active phase III Children's Oncology Group (COG) ALL trials. Processes include: (a) identifying infections as a targeted toxicity, (b) incorporation of infection-specific case report form questions, and (c) physician review of AEs with real-time data cleaning. Preliminary assessment of these processes suggests improved reporting, as well as opportunities for further improvement.

In cancer, linking epigenetic alterations to drivers of transformation has been difficult, in part because DNA methylation analyses must capture epigenetic variability, which is central to tumour heterogeneity and tumour plasticity. Here, by conducting a comprehensive analysis, based on information theory, of differences in methylation stochasticity in samples from patients with paediatric acute lymphoblastic leukaemia (ALL), we show that ALL epigenomes are stochastic and marked by increased methylation entropy at specific regulatory regions and genes. By integrating DNA methylation and single-cell gene-expression data, we arrived at a relationship between methylation entropy and gene-expression variability, and found that epigenetic changes in ALL converge on a shared set of genes that overlap with genetic drivers involved in chromosomal translocations across the disease spectrum. Our findings suggest that an epigenetically driven gene-regulation network, with UHRF1 (ubiquitin-like with PHD and RING finger domains 1) as a central node, links genetic drivers and epigenetic mediators in ALL. An information-theoretic analysis of DNA methylation in samples from patients with paediatric acute lymphoblastic leukaemia reveals that a regulatory set of driver genes harbour the greatest differences in methylation stochasticity.

There is growing evidence supporting an inherited basis for susceptibility to acute lymphoblastic leukemia (ALL) in children. In particular, we and others reported recurrent germline ETV6 variants linked to ALL risk, which collectively represent a novel leukemia predisposition syndrome. To understand the influence of ETV6 variation on ALL pathogenesis, we comprehensively characterized a cohort of 32 childhood leukemia cases arising from this rare syndrome. Of 34 nonsynonymous germline ETV6 variants in ALL, we identified 22 variants with impaired transcription repressor activity, loss of DNA binding, and altered nuclear localization. Missense variants retained dimerization with wild-type ETV6 with potentially dominant-negative effects. Whole-transcriptome and whole-genome sequencing of this cohort of leukemia cases revealed a profound influence of germline ETV6 variants on leukemia transcriptional landscape, with distinct ALL subsets invoking unique patterns of somatic cooperating mutations. 70% of ALL cases with damaging germline ETV6 variants exhibited hyperdiploid karyotype with characteristic recurrent mutations in NRAS, KRAS, and PTPN11. In contrast, the remaining 30% cases had a diploid leukemia genome and an exceedingly high frequency of somatic copy-number loss of PAX5 and ETV6, with a gene expression pattern that strikingly mirrored that of ALL with somatic ETV6-RUNX1 fusion. Two ETV6 germline variants gave rise to both acute myeloid leukemia and ALL, with lineage-specific genetic lesions in the leukemia genomes. ETV6 variants compromise its tumor suppressor activity in vitro with specific molecular targets identified by assay for transposase-accessible chromatin sequencing profiling. ETV6-mediated ALL predisposition exemplifies the intricate interactions between inherited and acquired genomic variations in leukemia pathogenesis.

Not available.

The Childhood Cancer Research Network (CCRN) was established by the Children's Oncology Group (COG) as a resource for epidemiologic studies of childhood cancer. The objective of this study was to evaluate the representativeness of CCRN and identify factors associated with enrollment.The number of US childhood patients with cancer diagnosed20 years of age enrolled in CCRN (2008-2015) was compared to expected counts, calculated from Surveillance, Epidemiology, and End Results incidence rates and US Census population estimates. Observed-to-expected ratios and corresponding 95% confidence intervals (CI) were estimated across sex, race, diagnosis age, calendar year, and cancer diagnosis groups. Multivariable linear regression models were generated to evaluate the association between open COG phase 3 therapeutic trials and CCRN enrollment rates.The 43,110 cases enrolled in CCRN represented 36% of the expected childhood cancers diagnosed from 2008 to 2015 (N = 120,118). CCRN enrollment ratios [95% CI] were highest among males (0.38 [95% CI, 0.37-0.38]), non-Hispanics (0.35 [95% CI, 0.35-0.36]), and those diagnosed from 1 to 4 years of age (0.50 [95% CI, 0.50-51]). Enrollment ratios varied by diagnosis group, with leukemia, myeloproliferative diseases, myelodysplastic diseases (0.55 [95% CI, 0.54-0.55]), and renal tumors (0.55 [95% CI, 0.53-0.58]) having the highest enrollment. After adjusting for year of diagnosis and cancer diagnosis, there was a 3.1% [95% CI, 0.6-5.6%] increase in CCRN enrollment during windows of open COG therapeutic trials.Despite enrolling only 36% of newly diagnosed cases, CCRN remains a valuable resource for investigators conducting childhood cancer etiology and survivorship research. The results of this study may inform efforts to improve enrollment on current and future COG nontherapeutic registry protocols.

PURPOSE Nelarabine is effective in inducing remission in patients with relapsed and refractory T-cell acute lymphoblastic leukemia (T-ALL) but has not been fully evaluated in those with newly diagnosed disease. PATIENTS AND METHODS From 2007 to 2014, Children’s Oncology Group trial AALL0434 (ClinicalTrials.gov identifier: NCT00408005 ) enrolled 1,562 evaluable patients with T-ALL age 1-31 years who received the augmented Berlin-Frankfurt-Muenster (ABFM) regimen with a 2 × 2 pseudo-factorial randomization to receive escalating-dose methotrexate (MTX) without leucovorin rescue plus pegaspargase (C-MTX) or high-dose MTX (HDMTX) with leucovorin rescue. Intermediate- and high-risk patients were also randomly assigned after induction to receive or not receive six 5-day courses of nelarabine that was incorporated into ABFM. Patients who experienced induction failure were nonrandomly assigned to HDMTX plus nelarabine. Patients with overt CNS disease (CNS3; ≥ 5 WBCs/μL with blasts) received HDMTX and were randomly assigned to receive or not receive nelarabine. All patients, except those with low-risk disease, received cranial irradiation. RESULTS The 5-year event-free and overall survival rates were 83.7% ± 1.1% and 89.5% ± 0.9%, respectively. The 5-year disease-free survival (DFS) rates for patients with T-ALL randomly assigned to nelarabine (n = 323) and no nelarabine (n = 336) were 88.2% ± 2.4% and 82.1% ± 2.7%, respectively ( P = .029). Differences between DFS in a four-arm comparison were significant ( P = .01), with no interactions between the MTX and nelarabine randomizations ( P = .41). Patients treated with the best-performing arm, C-MTX plus nelarabine, had a 5-year DFS of 91% (n = 147). Patients who received nelarabine had significantly fewer isolated and combined CNS relapses compared with patients who did not receive nelarabine (1.3% ± 0.63% v 6.9% ± 1.4%, respectively; P = .0001). Toxicities, including neurotoxicity, were acceptable and similar between all four arms. CONCLUSION The addition of nelarabine to ABFM therapy improved DFS for children and young adults with newly diagnosed T-ALL without increased toxicity.

Lineage switch in acute leukemia is rare – with the reported incidence across studies ranging from 0.6% of all leukemias to 6% of relapsed leukemias [1,2] – and strongly associated with presence of...

The rarity of mixed phenotype acute leukemia (MPAL) has precluded adequate data to incorporate minimal residual disease (MRD) monitoring into therapy. Fluidity in MPAL classification systems further complicates understanding its biology and outcomes; this includes uncertainty surrounding the impact of shifting diagnostic requirements even between iterations of the World Health Organization (WHO) classification. Our primary objective was to address these knowledge gaps. To do so, we analyzed clinicopathologic features, therapy, MRD, and survival in a centrally-reviewed, multicenter cohort of MPAL uniformly diagnosed by the WHO classification and treated with acute lymphoblastic leukemia (ALL) regimens. ALL induction therapy achieved an EOI MRD negative (

Boys with acute lymphoblastic leukemia (ALL) have historically experienced inferior survival compared to girls. This study determined whether sex-based disparities persist with contemporary therapy and whether patterns of treatment failure vary by sex.Patients 1 to 30.99 years old were enrolled on frontline Children's Oncology Group trials between 2004 and 2014. Boys received an additional year of maintenance therapy. Sex-based differences in the distribution of various prognosticators, event-free survival (EFS) and overall survival (OS), and subcategories of relapse by site were explored.A total of 8202 (54.4% male) B-cell ALL (B-ALL) and 1562 (74.3% male) T-cell ALL (T-ALL) patients were included. There was no sex-based difference in central nervous system (CNS) status. Boys experienced inferior 5-year EFS and OS (EFS, 84.6% ± 0.5% vs 86.0% ± 0.6%, P = .009; OS, 91.3% ± 0.4% vs 92.5% ± 0.4%, P = .02). This was attributable to boys with B-ALL, who experienced inferior EFS (hazard ratio [HR], 1.2; 95% confidence interval [95% CI], 1.1-1.3; P = .004) and OS (HR, 1.2; 95% CI, 1.0-1.4; P = .046) after adjustment for prognosticators. Inferior B-ALL outcomes in boys were attributable to more relapses (5-year cumulative incidence 11.2% ± 0.5% vs 9.6% ± 0.5%; P = .001), particularly involving the CNS (4.2% ± 0.3% vs 2.5% ± 0.3%; P .0001). There was no difference in isolated bone marrow relapses (5.4% ± 0.4% vs 6.2% ± 0.4%; P = .49). There were no sex-based differences in EFS or OS in T-ALL.Sex-based disparities in ALL persist, attributable to increased CNS relapses in boys with B-ALL. Studies of potential mechanisms are warranted. Improved strategies to identify and modify treatment for patients at highest risk of CNS relapse may have particular benefit for boys.

Adverse events are often misreported in clinical trials, leading to an incomplete understanding of toxicities. We aimed to test automated laboratory adverse event ascertainment and grading (via the ExtractEHR automated package) to assess its scalability and define adverse event rates for children with acute myeloid leukaemia and acute lymphoblastic leukaemia.For this retrospective cohort study from the Children's Oncology Group (COG), we included patients aged 0-22 years treated for acute myeloid leukaemia or acute lymphoblastic leukaemia at Children's Healthcare of Atlanta (Atlanta, GA, USA) from Jan 1, 2010, to Nov 1, 2018, at the Children's Hospital of Philadelphia (Philadelphia, PA, USA) from Jan 1, 2011, to Dec 31, 2014, and at the Texas Children's Hospital (Houston, TX, USA) from Jan 1, 2011, to Dec 31, 2014. The ExtractEHR automated package acquired, cleaned, and graded laboratory data as per Common Terminology Criteria for Adverse Events (CTCAE) version 5 for 22 commonly evaluated grade 3-4 adverse events (fatal events were not evaluated) with numerically based CTCAE definitions. Descriptive statistics tabulated adverse event frequencies. Adverse events ascertained by ExtractEHR were compared to manually reported adverse events for patients enrolled in two COG trials (AAML1031, NCT01371981; AALL0932, NCT02883049). Analyses were restricted to protocol-defined chemotherapy courses (induction I, induction II, intensification I, intensification II, and intensification III for acute myeloid leukaemia; induction, consolidation, interim maintenance, delayed intensification, and maintenance for acute lymphoblastic leukaemia).Laboratory adverse event data from 1077 patients (583 from Children's Healthcare of Atlanta, 200 from the Children's Hospital of Philadelphia, and 294 from the Texas Children's Hospital) who underwent 4611 courses (549 for acute myeloid leukaemia and 4062 for acute lymphoblastic leukaemia) were extracted, processed, and graded. Of the 166 patients with acute myeloid leukaemia, 86 (52%) were female, 80 (48%) were male, 96 (58%) were White, and 132 (80%) were non-Hispanic. Of the 911 patients with acute lymphoblastic leukaemia, 406 (45%) were female, 505 (55%) were male, 596 (65%) were White, and 641 (70%) were non-Hispanic. Patients with acute myeloid leukaemia had the most adverse events during induction I and intensification II. Hypokalaemia (one [17%] of six to 75 [48%] of 156 courses) and alanine aminotransferase (ALT) increased (13 [10%] of 134 to 27 [17%] of 156 courses) were the most prevalent non-haematological adverse events in patients with acute myeloid leukaemia, as identified by ExtractEHR. Patients with acute lymphoblastic leukaemia had the greatest number of adverse events during induction and maintenance (eight adverse events with prevalence ≥10%; induction and maintenance: anaemia, platelet count decreased, white blood cell count decreased, neutrophil count decreased, lymphocyte count decreased, ALT increased, and hypocalcaemia; induction: hypokalaemia; maintenance: aspartate aminotransferase [AST] increased and blood bilirubin increased), as identified by ExtractEHR. 187 (85%) of 220 total comparisons in 22 adverse events in four AAML1031 and six AALL0923 courses were substantially higher with ExtractEHR than COG-reported adverse event rates for adverse events with a prevalence of at least 2%.ExtractEHR is scalable and accurately defines laboratory adverse event rates for paediatric acute leukaemia; moreover, ExtractEHR seems to detect higher rates of laboratory adverse events than those reported in COG trials. These rates can be used for comparisons between therapies and to counsel patients treated on or off trials about the risks of chemotherapy. ExtractEHR-based adverse event ascertainment can improve reporting of laboratory adverse events in clinical trials.US National Institutes of Health, St Baldrick's Foundation, and Alex's Lemonade Stand Foundation.

Adolescent and young adult (AYA) patients 16–30 years old with high-risk acute lymphoblastic leukemia (HR-ALL) have inferior outcomes compared to younger HR-ALL patients. AALL0232 was a Phase 3 randomized Children’s Oncology Group trial for newly diagnosed HR B-ALL (1–30 years). Between 2004 and 2011, 3154 patients enrolled with 3040 eligible and evaluable for induction. AYA patients comprised 20% of patients (16–21 years, n = 551; 22–30 years, n = 46). 5-year event-free survival and overall survival was 65.4 ± 2.2% and 77.4 ± 2.0% for AYA patients compared to 78.1 ± 0.9% and 87.3 ± 0.7% for younger patients (p

Metabolomics may shed light on treatment response in childhood acute lymphoblastic leukemia (ALL), however, most assessments have analyzed bone marrow or cerebrospinal fluid (CSF), which are not collected during all phases of therapy. Blood is collected frequently and with fewer risks, but it is unclear whether findings from marrow or CSF biomarker studies may translate. We profiled end-induction plasma, marrow, and CSF from N = 10 children with B-ALL using liquid chromatography-mass spectrometry. We estimated correlations between plasma and marrow/CSF metabolite abundances detected in ≥ 3 patients using Spearman rank correlation coefficients (rs). Most marrow metabolites were detected in plasma (N = 661; 81%), and we observed moderate-to-strong correlations (median rs 0.62, interquartile range [IQR] 0.29–0.83). We detected 328 CSF metabolites in plasma (90%); plasma-CSF correlations were weaker (median rs 0.37, IQR 0.07–0.70). We observed plasma-marrow correlations for metabolites in pathways associated with end-induction residual disease (pyruvate, asparagine) and plasma-CSF correlations for a biomarker of fatigue (gamma-glutamylglutamine). There is considerable overlap between the plasma, marrow, and CSF metabolomes, and we observed strong correlations for biomarkers of clinically relevant phenotypes. Plasma may be suitable for biomarker studies in B-ALL.

Children with Down syndrome (DS) are 10-fold more likely to develop B-cell acute lymphoblastic leukemia (B-ALL), with a higher frequency of rearrangements resulting in overexpression of cytokine receptor-like factor 2 (CRLF2). Here, we investigated the impact of CRLF2 overexpression on B-cell progenitor proliferation, immunophenotype, and gene expression profile in the Dp(16)1Yey (Dp16) mouse model of DS compared with wild-type (WT) mice. CRLF2 overexpression enhanced immature B-lymphoid colony development and increased the proportion of less differentiated pre-pro-B cells, with a greater effect in Dp16 versus WT. In CRLF2-rearranged (CRLF2-R) B-ALL patient samples, cells with higher CRLF2 expression exhibited a less differentiated B-cell immunophenotype. CRLF2 overexpression resulted in a gene expression signature associated with E2F signaling both in Dp16 B-progenitors and in DS-ALL patient samples, and PI3K/mTOR and pan-CDK inhibitors, which reduce E2F-mediated signaling, exhibited cytotoxicity in CRLF2-R B-ALL cell lines and patient samples. CRLF2 overexpression alone in Dp16 stem and progenitor cells did not result in leukemic transformation in recipient mice. Thus, CRLF2 overexpression results in reduced B-cell differentiation and enhanced E2F signaling in Dp16 B-progenitor cells and DS-ALL patient samples. These findings suggest a functional basis for the high frequency of CRLF2-R in DS-ALL as well as a potential therapeutically targetable pathway.

Genetic alterations in the RUNX1 gene are associated with benign and malignant blood disorders, particularly of megakaryocyte and myeloid lineages. The role of RUNX1 in acute lymphoblastic leukemia (ALL) is less clear, particularly in terms of how germline genetic variation influences the predisposition to this type of leukemia. Sequencing DNA of 4836 children with B cell ALL (B-ALL) and 1354 with T cell ALL (T-ALL), we identified 31 and 18 germline RUNX1 variants, respectively. RUNX1 variants in B-ALL consistently showed minimal damaging effects. In contrast, 6 T-ALL–related variants resulted in drastic loss of RUNX1 activity as a transcription activator in vitro. Ectopic expression of dominant-negative RUNX1 variants in human CD34(+) cells repressed differentiation into erythroid cells, megakaryocytes, and T cells, while promoting myeloid cell development. Chromatin immunoprecipitation sequencing of T-ALL models showed distinctive patterns of RUNX1 binding by variant proteins. Further whole-genome sequencing identified the JAK3 mutation as the most frequent somatic genomic abnormality in T-ALL with germline RUNX1 variants. Cointroduction of RUNX1 variant and JAK3 mutation in hematopoietic stem and progenitor cells in mice gave rise to T-ALL with the early T cell precursor phenotype. Taken together, these results indicate that RUNX1 is an important predisposition gene for T-ALL and point to biology of RUNX1-mediated leukemogenesis in the lymphoid lineages.

Background: Children with hematologic malignancies, especially those who receive intensive chemotherapy, are at high risk for invasive mold infections (IMI) that confer substantial mortality. Randomized controlled trials support the use of anti-fungal prophylaxis with anti-mold activity as an optimal strategy for risk reduction in this population, but studies outlining the practical application of evidence-based recommendations are lacking. Procedure: We conducted a 15-year, single-institution retrospective review of children with hematologic malignancies treated with chemotherapy to determine the incidence of proven or probable IMI diagnosed between 2006 and 2020 and to identify the host and disease factors associated with IMI risk. We then compared the incidence and type of IMI and related factors before and after 2016 implementation of an evidence-based, risk-adapted anti-fungal prophylaxis algorithm that broadened coverage to include molds in patients at highest risk for IMI. Multivariable linear regression was used to determine factors related to IMI risk. Results: We identified 61 cases of proven or probable IMI in 1,456 patients diagnosed with hematologic malignancies during the study period (4.2%). Implementation of an anti-fungal prophylaxis algorithm reduced the IMI incidence in this population from 4.8% to 2.9%. After multivariable analysis, both Hispanic ethnicity and cancer diagnosis prior to 2016 were significantly associated with risk for IMI. Conclusion: An evidence-based, risk-adapted approach to anti-fungal prophylaxis for children with hematologic malignancies is an effective strategy to reduce incidence of IMI.

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Here, using whole-genome, exome and transcriptome sequencing of 2,754 childhood patients with ALL, we find that, despite a generally low mutation burden, ALL cases harbor a median of four putative somatic driver alterations per sample, with 376 putative driver genes identified varying in prevalence across ALL subtypes. Most samples harbor at least one rare gene alteration, including 70 putative cancer driver genes associated with ubiquitination, SUMOylation, noncoding transcripts and other functions. In hyperdiploid B-ALL, chromosomal gains are acquired early and synchronously before ultraviolet-induced mutation. By contrast, ultraviolet-induced mutations precede chromosomal gains in B-ALL cases with intrachromosomal amplification of chromosome 21. We also demonstrate the prognostic significance of genetic alterations within subtypes. Intriguingly, DUX4- and KMT2A-rearranged subtypes separate into CEBPA/FLT3- or NFATC4-expressing subgroups with potential clinical implications. Together, these results deepen understanding of the ALL genomic landscape and associated outcomes.

Background: End-induction minimal residual disease (MRD) is the strongest predictor of relapse in paediatric acute lymphoblastic leukaemia (ALL), but an understanding of the biological pathways underlying early treatment response remains elusive. We hypothesized that metabolomic profiling of diagnostic bone marrow plasma could provide insights into the underlying biology of early treatment response and inform treatment strategies for high-risk patients. Methods: We performed global metabolomic profiling of samples from discovery (N = 93) and replication (N = 62) cohorts treated at Texas Children's Hospital. Next, we tested the cytotoxicity of drugs targeting central carbon metabolism in cell lines and patient-derived xenograft (PDX) cells. Findings: Metabolite set enrichment analysis identified altered central carbon and amino acid metabolism in MRD-positive patients from both cohorts at a 5% false discovery rate. Metabolites from these pathways were used as inputs for unsupervised hierarchical clustering. Two distinct clusters were identified, which were independently associated with MRD after adjustment for immunophenotype, cytogenetics, and NCI risk group. Three nicotinamide phosphoribosyltransferase (NAMPT) inhibitors, which reduce glycolytic/TCA cycle activities, demonstrated nanomolar-range cytotoxicity in B- and T-ALL cell lines and PDX cells. Interpretation: This study provides new insights into the role of central carbon metabolism in early treatment response and as a potential targetable pathway in high-risk disease. Funding: American Society of Hematology; Baylor College of Medicine Department of Paediatrics; Cancer Prevention and Research Institute of Texas; the Lynch family; St. Baldrick's Foundation with support from the Micaela's Army Foundation; United States National Institutes of Health. Keywords: Acute lymphoblastic leukaemia, Minimal residual disease, Epidemiology, NAMPT, NAMPT inhibitors

Children with Down syndrome (DS) have a 20-fold increased risk of acute lymphoblastic leukemia (ALL) and distinct somatic features, including CRLF2 rearrangement in ∼50% of cases; however, the role of inherited genetic variation in DS-ALL susceptibility is unknown. We report the first genome-wide association study of DS-ALL, comprising a meta-analysis of 4 independent studies, with 542 DS-ALL cases and 1192 DS controls. We identified 4 susceptibility loci at genome-wide significance: rs58923657 near IKZF1 (odds ratio [OR], 2.02; Pmeta = 5.32 × 10-15), rs3731249 in CDKN2A (OR, 3.63; Pmeta = 3.91 × 10-10), rs7090445 in ARID5B (OR, 1.60; Pmeta = 8.44 × 10-9), and rs3781093 in GATA3 (OR, 1.73; Pmeta = 2.89 × 10-8). We performed DS-ALL vs non-DS ALL case-case analyses, comparing risk allele frequencies at these and other established susceptibility loci (BMI1, PIP4K2A, and CEBPE) and found significant association with DS status for CDKN2A (OR, 1.58; Pmeta = 4.1 × 10-4). This association was maintained in separate regression models, both adjusting for and stratifying on CRLF2 overexpression and other molecular subgroups, indicating an increased penetrance of CDKN2A risk alleles in children with DS. Finally, we investigated functional significance of the IKZF1 risk locus, and demonstrated mapping to a B-cell super-enhancer, and risk allele association with decreased enhancer activity and differential protein binding. IKZF1 knockdown resulted in significantly higher proliferation in DS than non-DS lymphoblastoid cell lines. Our findings demonstrate a higher penetrance of the CDKN2A risk locus in DS and serve as a basis for further biological insights into DS-ALL etiology.

The Children’s Cancer Group 1991 study was a clinical trial for children with National Cancer Institute standard-risk acute lymphoblastic leukemia (ALL). This trial demonstrated that 5 doses of vincristine and escalating IV methotrexate (MTX) without leucovorin rescue in the interim maintenance (IM) phases resulted in superior event-free survival (EFS) when compared with 2 doses of vincristine, oral (PO) MTX, PO mercaptopurine, and dexamethasone. This report describes a favorable outcome of this regimen in patients with Down syndrome (DS). Forty-four patients with DS were randomized to the arms containing PO MTX during IM, and 31 to those containing IV MTX. Ten-year EFS rates for patients with DS randomized to IV MTX vs PO MTX were 94.4% ± 5.4% vs 81.5% ± 6.6%, respectively. IV methotrexate with strict escalation parameters, as given in this study, was well tolerated, although the mean total tolerated dose received was lower in patients with DS than in those without DS. There was no increase in hepatic toxicity, systemic infections, or treatment-related deaths in patients with DS during IM on either the IV or PO MTX arms, as compared with those without DS. The incidence of mucositis was increased in patients with DS as compared with patients without DS, particularly among patients who received IV MTX. This trial was registered at www.clinicaltrials.gov as #NCT00005945.

Introduction: While end-induction minimal residual disease (MRD) is the strongest prognostic factor for relapsed ALL, approximately half of all relapses occur in children who are MRD negative. Latino ethnicity is also a risk factor for relapse. To further explore these associations, we conducted an interim analysis of risk factors for relapse in a large multi-ethnic population of children diagnosed with ALL. Methods: The REDIAL Consortium includes patients diagnosed with ALL at six major pediatric cancer centers in the Southwestern U.S. The study period was 2004 to 2018, and we included individuals who were 1-23 years of age when diagnosed with ALL. Time to relapse was defined as time from ALL diagnosis to the initial relapse event, with individuals censored at date of death, last follow-up, or bone marrow transplant. Demographic and clinical factors evaluated included race/ethnicity (Latino, non-Latino Black, non-Latino White, non-Latino other), sex, age at diagnosis (1-5, 6-10, 11-15, >15 years), ALL immunophenotype (B-cell, T-cell), National Cancer Institute (NCI) risk group, central nervous system involvement, enrollment on a Children’s Oncology Group clinical trial, end-induction disease failure, and end-induction bone marrow flow cytometric MRD. Cox proportional hazards models were used to calculate adjusted hazards ratios (HRs) and 95% confidence intervals (CIs). Analyses were further stratified based on end-induction MRD status (positive ≥0.01%, negative Results: Overall, there were 1,710 ALL patients with a median age at diagnosis of 5 years (interquartile range: 3-11 years). The majority of patients were Latino (60.1%) and male (56.9%). Of the 379 MRD-positive patients, 74 (19.5%) relapsed, compared to 138 of 1,233 (11.2%) MRD-negative patients (p15 vs. 1-5 years, HR=1.98, 95% CI: 1.19-3.29), and NCI high-risk group (HR=1.74, 95% CI: 1.20-2.52), while patients enrolled on a clinical trial were less likely to relapse (HR=0.76, 95% CI: 0.57-0.99). Among MRD-positive patients, Latinos were less likely to relapse (HR=0.60, 95% CI: 0.33-0.99) compared to non-Latino Whites, whereas Latinos who were MRD negative were more likely to relapse (HR=1.68, 95% CI: 1.09-2.59). Conclusion: In a large contemporary multi-ethnic cohort of >1,700 children with ALL, we observed significant disparities in relapse by MRD status, age at diagnosis, NCI risk group, clinical trial enrollment, and race/ethnicity. Notably, nearly 65% of relapse events occurred in MRD-negative patients. Further analyses are ongoing in REDIAL to evaluate the impact of other factors including cytogenetics and novel biomarkers of relapse. Citation Format: Pagna Sok, Austin L. Brown, Olga A. Taylor, M. Brooke Bernhardt, Juan C. Bernini, Rodrigo A. Erana, Timothy Griffin, Kenneth Heym, Van T. Huynh, Laura Klesse, Kathleen Ludwig, Sandi L. Pruitt, Karen R. Rabin, Michael E. Scheurer, Philip J. Lupo. Disparities in relapse among a large multi-ethnic population of children diagnosed with acute lymphoblastic leukemia (ALL): A report from the Reducing Ethnic Disparities in Acute Leukemia (REDIAL) Consortium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3633.

Background: Children with Down syndrome (DS) have an increased risk of acute lymphoblastic leukemia (ALL) and are more likely to experience morbidity and mortality from infectious toxicities during treatment compared to those without DS. We sought to characterize genetic risk factors for sepsis among individuals with DS-ALL. Methods: We performed a germline genome-wide association (GWAS) study for sepsis among 264 subjects with DS-ALL treated on Children’s Oncology Group (COG) protocols AALL0932 (N=181) and AALL1131 (N=83), for newly-diagnosed standard risk and high risk B-ALL, respectively. Sepsis was defined using Common Terminology Criteria for Adverse Events (v4.0), with a microbiologically confirmed grade 4 or 5 sepsis event reported during any phase of treatment to define the case and comparison groups. Germline genotyping on the Affymetrix SNP 6.0 or Illumina Omni 2.5Exome arrays was imputed to the Haplotype Reference Consortium panel and filtered for quality control. Logistic regression models were used to compare individuals with DS-ALL who experienced sepsis to those who never developed sepsis during treatment. Models were adjusted for principal components of population structure and COG protocol. Analyses included autosomal variants with a minor allele frequency >1% and excluded chromosome 21. Results: We identified 29 individuals (10.9%) with DS-ALL who developed one or more sepsis events during treatment. In genome-wide analyses, we observed 52 variants in eight genomic loci associated with sepsis at P Conclusion: We identified evidence of genetic associations for sepsis risk in DS-ALL. These findings suggest zinc homeostasis may be an important factor mediating risk of sepsis during treatment of individuals with DS-ALL. Confirmatory studies and validation in additional cohorts are ongoing. Citation Format: Melissa A. Richard, Meenakshi Devidas, Wenjian Yang, John P. Woodhouse, Vilmarie Rodriguez, Johann K. Hitzler, Reuven J. Schore, Anne L. Angiolillo, Michael J. Burke, Wanda L. Salzer, Elizabeth A. Raetz, Mignon L. Loh, Stephen P. Hunger, Jun J. Yang, Philip J. Lupo, Karen R. Rabin. A genome-wide association study identifies novel sepsis risk loci in children with Down syndrome-associated acute lymphoblastic leukemia: A report from the Children’s Oncology Group [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2002.

Introduction: Methotrexate (MTX) is a key component of curative chemotherapy for pediatric acute lymphoblastic leukemia (ALL). However, delivery of MTX is often interrupted by dose-limiting acute neurotoxicity, which manifests as seizures, stroke-like symptoms, or altered mental status. Because incidence and risk factors for MTX neurotoxicity are poorly defined, we evaluated clinical and demographic predictors of MTX neurotoxicity using the multi-ethnic REDIAL Consortium. Methods: The REDIAL cohort includes pediatric patients diagnosed with ALL at six treatment centers in the southwestern U.S. This interim analysis evaluated 756 patients age 1-21 years diagnosed with B-ALL (2005-2018). Electronic health records were reviewed to determine race/ethnicity (Latino, non-Latino White, non-Latino Black, or Other), body mass index, sex, age, and intravenous (IV) MTX dose. Applying Ponte di Legno criteria, acute MTX neurotoxicity was defined as neurologic episodes occurring Results: The study population was 56.6% Latino, 52.8% male, 41.4% treated with >5g/m2 IV MTX, and diagnosed at a median age of 5 years. Overall, 15.5% (95% CI: 12.9-18.3%) of patients experienced neurotoxic events (n=117), including 1.9% (n=14, 95% CI: 1.0-3.1%) during induction, 13.0% (n=98, 95% CI: 10.7-15.6%) during post-induction, and 0.7% (n=5, 95% CI: 0.2-1.5%) during maintenance therapy. Ethnic differences were not statistically significant during induction or maintenance phases. Compared to non-Latinos, post-induction neurotoxicity was significantly more frequent among Latinos (aOR = 2.87, 95% CI: 1.68-5.10), with disparities observed during consolidation, interim maintenance and delayed intensification phases. Exposure to >5g/m2 IV MTX (aOR = 2.16, 95% CI: 1.08-3.24) and older age at diagnosis (aOR = 1.16, 95% CI: 1.08-1.24) were also associated with a significantly more post-induction neurotoxicity. No factors evaluated were significantly associated with neurotoxicity during induction and maintenance therapy. Conclusions: MTX neurotoxicity disproportionally affects Latino children during ALL post-induction therapy. Additional work is warranted to identify risk factors for neurotoxicity during induction and maintenance therapy as well as the specific clinical and host biological factors responsible for post-induction ethnic differences in MTX neurotoxicity. Citation Format: Austin L. Brown, Rachel D. Harris, Olga A. Taylor, Melanie B. Bernhardt, Juan C. Bernini, Rodrigo A. Erana, Timothy Griffin, Kenneth Heym, Van T. Huynh, Kathleen Ludwig, Avner Meoded, Sandi L. Pruitt, Philip J. Lupo, Karen R. Rabin, Michael E. Scheurer. Ethnic disparities in methotrexate neurotoxicity during pediatric acute lymphoblastic leukemia therapy: A report from the Reducing Ethnic Disparities in Acute Leukemia (REDIAL) Consortium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3636.

Background: Acute lymphoblastic leukemia (ALL) remains a leading cause of death in children and adolescents. We have demonstrated that Hispanic enclaves - neighborhoods with high proportions of Spanish-speaking residents, recent immigrants, and ethnic-specific businesses - are associated with inferior overall survival in children with ALL. However, associations of enclaves with other outcomes remain poorly understood. In the present study, our objective was to determine whether residence in an enclave was associated with end-induction minimal residual disease (MRD), a strong predictor of ALL mortality. Methods: This was a retrospective study of N=142 children aged 0-18 years, treated at Texas Children’s Hospital (Houston, TX) from 2007-2018. MRD was defined as ≥0.01% leukemic blasts in bone marrow at day 29 of therapy. We used the 2010 census tract geography and a modified version of the Hispanic enclave index to identify enclaves. We assigned an enclave index score to each census tract, computed quartiles based on the statewide distribution, and mapped children to quartiles based on address at diagnosis (Q1: least ethnically distinct neighborhoods; Q4: most ethnically distinct neighborhoods). Data on sex, self-reported race/ethnicity, National Cancer Institute (NCI) risk group, primary language, and ALL cytogenetics were abstracted from electronic health records. Cytogenetics were considered either unfavorable (BCR-ABL1 fusion, KMT2A rearrangement, hypodiploidy, or intrachromosomal amplification of chromosome 21) or favorable (ETV6-RUNX1 fusion, double trisomies of chromosomes 4 and 10)/neutral (neither favorable nor unfavorable). We estimated the odds ratio (OR) and 95% confidence interval (95% CI) of MRD according to enclave index score using logistic regression. Results: Neither individual ethnicity nor primary language varied by MRD status, but a greater proportion of MRD-positive children lived in the most ethnically distinct neighborhoods (53% vs. 36%, p=0.04). Enclave index score was associated with MRD after adjusting for sex, NCI risk group, and cytogenetics (OR 1.57 per quartile increment, 95% CI 1.09-2.33). We also observed non-significantly increased odds of MRD among children in Q3 (OR 1.53, 95% CI 0.41-6.55) and Q4 (OR 2.84, 0.83-11.58) relative to Q1. Conclusions: We found that residence in a Hispanic enclave was associated with MRD in children with ALL. Neither ethnicity nor primary language differed by MRD status, suggesting that these did not confound the association with enclave index score. Neighborhood factors may influence early treatment outcomes in ALL, and children living in Hispanic enclaves may constitute a high-risk population. Citation Format: Joshua P. Muniz, John P. Woodhouse, Amy E. Hughes, Sandi L. Pruitt, Karen R. Rabin, Michael E. Scheurer, Philip J. Lupo, Jeremy M. Schraw. Association between residence in a Hispanic enclave and end-induction minimal residual disease among children with acute lymphoblastic leukemia in Texas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3671.

With modern chemotherapy, approximately 90% of patients with pediatric acute lymphoblastic leukemia are now cured. However, subsets of patients can be identified who remain at very high risk of relapse with expected 4-year disease-free survival rates

RUNX1 is a transcription factor critical for definitive hematopoiesis and genetic alterations in RUNX1 have been implicated in both benign and malignant blood disorders, particularly of the megakaryocyte and myeloid lineages. Somatic RUNX1 mutations are reported in B- and T-cell acute lymphoblastic leukemia (B-ALL and T-ALL), but germline genetic variation of RUNX1 in these lymphoid malignancies have not been comprehensively investigated. Sequencing 4,836 children with B-ALL and 1,354 cases of T-ALL, we identified 31 and 18 unique germline RUNX1 variants in these two ALL subtypes, respectively. RUNX1 variants in B-ALL were predicted to have minimal impact. By contrast, 54.5% of variants in T-ALL result in complete or partial loss of RUNX1 activity as a transcription activator in vitro, with dominant negative effects for 4 variants. Ectopic expression of dominant negative deleterious RUNX1 variants in human CD34+ cells repressed differentiation into erythroid, megakaryocytes, and T cells, while promoting differentiation towards myeloid cells. We then performed chromatin immunoprecipitation profiling in isogenic T-ALL models with variants introduced by genome editing of endogenous RUNX1. We observed highly distinctive patterns of DNA binding and target genomic loci by RUNX1 proteins encoded by the truncating vs missense variants. The p.G365R RUNX1 variant resulted in a novel methylation site in RUNX1 and alteration in its interaction with CBFβ. Further whole genome sequencing showed that JAK3 mutation was the most frequent somatic genomic abnormality in T-ALL with germline RUNX1 variants. Consistently, co-introduction of RUNX1 variant and JAK3 mutation in hematopoietic stem and progenitor cells in mouse gave rise to T-ALL with early T-cell precursor phenotype in vivo, compared to thymic T-ALL seen in mice with JAK3 mutation alone. Taken together, these results indicated that RUNX1 is an important predisposition gene for ALL, especially in T-ALL and also pointed to novel biology of RUNX1-mediated leukemogenesis in the lymphoid lineages.

Background Carboxypeptidase G2 (CPDG2 ; glucarpidase) is a rescue drug for patients at risk for kidney injury from high-dose methotrexate (MTX). As there are no strategies for predicting patients who will require CDPG2 , we evaluated the role of demographic, clinical, and genetic factors for CPDG2 use. Procedure Cases who received CPDG2 and controls who did not were identified by chart review of acute lymphoblastic leukemia (ALL) patients who received MTX doses between 1000 and 5000 mg/m2 between 2010 and 2017. We used multivariable Bayesian logistic regression to evaluate the association of CPDG2 use with demographic and clinical variables and, on a subset of patients, with genetic ancestry and 49 single nucleotide variants previously associated with MTX toxicity. Results We identified 423 patients who received 1592 doses of MTX. Of the 18 patients who received CPDG2 , 17 (94%) were Hispanic. No patients who received 1000 or 2000 mg/m2 of MTX received CPDG2 . Hispanic ethnicity (odds ratio: 4.68; 95% compatibility interval: 1.63-15.06) and older age (1.87 [1.17-3.17]) were associated with receiving CPDG2 . Of the 177 patients in the genomic cohort, 11 received CPDG2 . Each additional G allele of rs7317112 in ABCC4 increased the odds of requiring CPDG2 (3.10 [1.12-6.75]). Six other loci (NTRK1/rs10908521, TSG1/rs9345389, STT3B/rs1353327, SCLO1B1/rs4149056, GATA3/rs3824662, ARID5B/rs10821936) demonstrated probabilities of association between 88% and 97%. Conclusion We demonstrated that demographic characteristics, including Hispanic ethnicity and age, are associated with CPDG2 use. Additionally, we provide evidence that inherited genetic variation is associated with risk of requiring CPDG2 . If validated in independent populations, this information could be leveraged to develop targeted toxicity prevention strategies for children with ALL.

Purpose: AALL0932 evaluated two randomized maintenance interventions to optimize disease-free survival (DFS) while reducing the burden of therapy in children with newly diagnosed NCI standard-risk (SR) B-acute lymphoblastic leukemia (B-ALL). Methods: AALL0932 enrolled 9,229 patients with B-ALL; 2,364 average-risk (AR) patients were randomly assigned (2 × 2 factorial design) at the start of maintenance therapy to vincristine/dexamethasone pulses every 4 (VCR/DEX4) or every 12 (VCR/DEX12) weeks, and a starting dose of weekly oral methotrexate of 20 mg/m2 (MTX20) or 40 mg/m2 (MTX40). Results: Five-year event-free survival and overall survival (OS) from enrollment (with 95% CIs), for all eligible and evaluable SR B-ALL patients (n = 9,226), were 92.0% (91.1% and 92.8%) and 96.8% (96.2% and 97.3%), respectively. The 5-year DFS and OS from the start of maintenance for randomly assigned AR patients were 94.6% (93.3% and 95.9%) and 98.5% (97.7% and 99.2%), respectively. The 5-year DFS and OS for patients randomly assigned to receive VCR/DEX4 (n = 1,186) versus VCR/DEX12 (n = 1,178) were 94.1% (92.2% and 96.0%) and 98.3% (97.2% and 99.4%) v 95.1% (93.3% and 96.9%) and 98.6% (97.7% and 99.6%), respectively ( P = .86 and .69). The 5-year DFS and OS for AR patients randomly assigned to receive MTX20 versus MTX40 were 95.1% (93.3% and 96.8%) and 98.8% (97.9% and 99.7%) v 94.2% (92.2% and 96.1%) and 98.1% (97.0% and 99.2%), respectively ( P = .92 and .89). Conclusions: The 0NCI-SR AR B-ALL who received VCR/DEX12 had outstanding outcomes despite receiving one third of the vincristine/dexamethasone pulses previously used as standard of care on Children's Oncology Group (COG) trials. The higher starting dose of MTX of 40 mg/m2/week did not improve outcomes when compared with 20 mg/m2/week. The decreased frequency of vincristine/dexamethasone pulses has been incorporated into frontline COG B-ALL trials to decrease the burden of therapy for patients and their families.