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NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Pediatric Aggressive Mature B-Cell Lymphomas include recommendations for the diagnosis and management of pediatric patients with primary mediastinal large B-cell lymphoma (PMBL) and sporadic variants of Burkitt lymphoma and diffuse large B-cell lymphoma. PMBL is now considered as a distinct entity arising from mature thymic B-cells accounting for 2% of mature B-cell lymphomas in children and adolescents. This discussion section includes the recommendations outlined in the NCCN Guidelines for the diagnosis and management of pediatric patients with PMBL.

VAF concordance

Supplementary Data file including supplementary methods and clinical case vignettes.

Reasons for not using recommended targeted therapy.

Patient sequencing data, by patient number and diagnosis.

PURPOSE Children's Oncology Group (COG) AALL0331 tested whether pegaspargase intensification on a low-intensity chemotherapy backbone would improve the continuous complete remission (CCR) rate in a low-risk subset of children with standard-risk B-acute lymphoblastic leukemia (ALL). METHODS AALL0331 enrolled 5,377 patients with National Cancer Institute standard-risk B-ALL (age 1-9 years, WBC < 50,000/μL) between 2005 and 2010. Following a common three-drug induction, a cohort of 1,857 eligible patients participated in the low-risk ALL random assignment. Low-risk criteria included no extramedullary disease, < 5% marrow blasts by day 15, end-induction marrow minimal residual disease < 0.1%, and favorable cytogenetics ( ETV6-RUNX1 fusion or simultaneous trisomies of chromosomes 4, 10, and 17). Random assignment was to standard COG low-intensity therapy (including two pegaspargase doses, one each during induction and delayed intensification) with or without four additional pegaspargase doses at 3-week intervals during consolidation and interim maintenance. The study was powered to detect a 4% improvement in 6-year CCR rate from 92% to 96%. RESULTS The 6-year CCR and overall survival (OS) rates for the entire low-risk cohort were 94.7% ± 0.6% and 98.7% ± 0.3%, respectively. The CCR rates were similar between arms (intensified pegaspargase 95.3% ± 0.8% v standard 94.0% ± 0.8%; P = .13) with no difference in OS (98.1% ± 0.5% v 99.2% ± 0.3%; P = .99). Compared to a subset of standard-risk study patients given identical therapy who had the same early response characteristics but did not have favorable or unfavorable cytogenetics, outcomes were significantly superior for low-risk patients (CCR hazard ratio 1.95; P = .0004; OS hazard ratio 5.42; P < .0001). CONCLUSION Standard COG therapy without intensified pegaspargase, which can easily be given as an outpatient with limited toxicity, cures nearly all children with B-ALL identified as low-risk by clinical, early response, and favorable cytogenetic criteria.

Mutations in the CBL gene were first identified in adults with various myeloid malignancies. Some patients with juvenile myelomonocytic leukemia (JMML) were also noted to harbor mutations in CBL, but were found to have generally less aggressive disease courses compared to patients with other forms of Ras pathway-mutant JMML. Importantly, and in contrast to most reports in adults, the majority of CBL mutations in JMML patients are germline with acquired uniparental disomy occurring in affected marrow cells. Here, we systematically studied a large cohort of 33 JMML patients with CBL mutations and found that this disease is highly diverse in presentation and overall outcome. Moreover, we discovered somatically acquired CBL mutations in 15% of pediatric patients who presented with more aggressive disease. Neither clinical features nor methylation profiling were able to distinguish patients with somatic CBL mutations from those with germline CBL mutations, highlighting the need for germline testing. Overall, we demonstrate that disease courses are quite heterogeneous even among patients with germline CBL mutations. Prospective clinical trials are warranted to find ideal treatment strategies for this diverse cohort of patients.

PURPOSE Children’s Oncology Group (COG) AALL0331 tested whether intensified postinduction therapy that improves survival in children with high-risk B-cell acute lymphoblastic leukemia (ALL) would also improve outcomes for those with standard-risk (SR) ALL. PATIENTS AND METHODS AALL0331 enrolled 5,377 patients between 2005 and 2010. All patients received a 3-drug induction with dexamethasone, vincristine, and pegaspargase (PEG) and were then classified as SR low, SR average, or SR high. Patients with SR-average disease were randomly assigned to receive either standard 4-week consolidation (SC) or 8-week intensified augmented Berlin-Frankfurt-Münster (BFM) consolidation (IC). Those with SR-high disease were nonrandomly assigned to the full COG-augmented BFM regimen, including 2 interim maintenance and delayed intensification phases. RESULTS The 6-year event-free survival (EFS) rate for all patients enrolled in AALL0331 was 88.96% ± 0.46%, and overall survival (OS) was 95.54% ± 0.31%. For patients with SR-average disease, the 6-year continuous complete remission (CCR) and OS rates for SC versus IC were 87.8% ± 1.3% versus 89.1% ± 1.2% ( P = .52) and 95.8% ± 0.8% versus 95.2% ± 0.8% ( P = 1.0), respectively. Those with SR-average disease with end-induction minimal residual disease (MRD) of 0.01% to < 0.1% had an inferior outcome compared with those with lower MRD and no improvement with IC (6-year CCR: SC, 77.5% ± 4.8%; IC, 77.1% ± 4.8%; P = .71). At 6 years, the CCR and OS rates among 635 nonrandomly treated patients with SR-high disease were 85.55% ± 1.49% and 92.97% ± 1.08%, respectively. CONCLUSION The 6-year OS rate for > 5,000 children with SR ALL enrolled in AALL0331 exceeded 95%. The addition of IC to treatment for patients with SR-average disease did not improve CCR or OS, even in patients with higher MRD, in whom it might have been predicted to provide more value. The EFS and OS rates are excellent for this group of patients with SR ALL, with particularly good outcomes for those with SR-high disease.

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.

Objectives We evaluated the length of time immunocompromised children (ICC) remain positive for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), identified factors associated with viral persistence, and determined cycle threshold (C T) values of children with viral persistence as a surrogate of viral load. Methods We conducted a retrospective cohort study of ICC at a pediatric hospital from March 2020 to March 2021. Immunocompromised status was defined as primary, secondary, or acquired due to medical comorbidities/immunosuppressive treatment. The primary outcome was time to first of two consecutive negative SARS‐CoV‐2 polymerase chain reaction (PCR) tests at least 24 hours apart. Testing of sequential clinical specimens from the same subject was conducted using the Centers for Disease Control (CDC) 2019‐nCoV real‐time reverse transcriptase (RT)‐PCR Diagnostic Panel assay. Descriptive statistics, Kaplan–Meier curve median event times and log‐rank tests were used to compare outcomes between groups. Results Ninety‐one children met inclusion criteria. Median age was 15.5 years (interquartile range [IQR] 8–18), 64% were male, 58% were White, and 43% were Hispanic/Latinx. Most (67%) were tested in outpatient settings and 58% were asymptomatic. The median time to two negative tests was 42 days (IQR 25.0–55.0), with no differences in median time by illness presentation or level of immunosuppression. Seven children had more than one sample available for repeat testing, and five of seven (71%) children had initial C T values of 6 weeks and moderate to high viral load.

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.

Despite a remarkable increase in the genomic profiling of cancer, integration of genomic discoveries into clinical care has lagged behind. We report the feasibility of rapid identification of targetable mutations in 153 pediatric patients with relapsed/refractory or high-risk leukemias enrolled on a prospective clinical trial conducted by the LEAP Consortium. Eighteen percent of patients had a high confidence Tier 1 or 2 recommendation. We describe clinical responses in the 14% of patients with relapsed/refractory leukemia who received the matched targeted therapy. Further, in order to inform future targeted therapy for patients, we validated variants of uncertain significance, performed ex vivo drug-sensitivity testing in patient leukemia samples, and identified new combinations of targeted therapies in cell lines and patient-derived xenograft models. These data and our collaborative approach should inform the design of future precision medicine trials. Significance: Patients with relapsed/refractory leukemias face limited treatment options. Systematic integration of precision medicine efforts can inform therapy. We report the feasibility of identifying targetable mutations in children with leukemia and describe correlative biology studies validating therapeutic hypotheses and novel mutations. See related commentary by Bornhauser and Bourquin, p. 1322. This article is highlighted in the In This Issue feature, p. 1307

Background Mediastinal masses in children may present with compression of the great vessels and airway. An interdisciplinary plan for rapid diagnosis, acute management, and treatment prevents devastating outcomes and optimizes care. Emergency pretreatment with steroids or radiation is more likely to be administered when care is variable, which may delay and complicate diagnosis and treatment. Strategies to standardize care and expedite diagnosis may improve acute patient safety and long-term outcomes. Aims The aim of this quality improvement project was to decrease time from presentation to diagnostic biopsy for children with an anterior mediastinal mass by 50% over 3 years within a tertiary healthcare system. Methods This quality improvement project involved a single center with data collected and analyzed retrospectively and prospectively for 71 patients presenting with anterior mediastinal mass between February 2008 and January 2018. The Model for Improvement was utilized for project design and development of a driver diagram and smart aim. An algorithm was implemented to facilitate communication between teams and standardize initial care of patients with mediastinal masses. The algorithm underwent multiple Plan-Do-Study-Act (PDSA) cycles. Data were collected before and after algorithm implementation and between each PDSA cycle. The primary outcome measure included time from presentation to biopsy, which was monitored with a statistical process control chart. Several process measures were evaluated with Student's t-tests including administration of emergency pretreatment. Results Nineteen patients preintervention and 52 patients postintervention were included in the analysis. Time from presentation to biopsy significantly decreased from 48 h at baseline to 24 h postimplementation. Although not statistically significant, emergency pretreatment decreased from a baseline of 26.3% to 6.7% postimplementation. Conclusion Implementation of a diagnostic and management algorithm coordinating care among multidisciplinary teams significantly reduced time to biopsy for children presenting with mediastinal mass and may result in decreased use of emergent pretreatment.

Children's Oncology Group (COG) AALL0331 tested whether pegaspargase intensification on a low-intensity chemotherapy backbone would improve the continuous complete remission (CCR) rate in a low-risk subset of children with standard-risk B-acute lymphoblastic leukemia (ALL). METHODS: AALL0331 enrolled 5,377 patients with National Cancer Institute standard-risk B-ALL (age 1-9 years, WBC < 50,000/μL) between 2005 and 2010. Following a common three-drug induction, a cohort of 1,857 eligible patients participated in the low-risk ALL random assignment. Low-risk criteria included no extramedullary disease, < 5% marrow blasts by day 15, end-induction marrow minimal residual disease < 0.1%, and favorable cytogenetics (ETV6-RUNX1 fusion or simultaneous trisomies of chromosomes 4, 10, and 17). Random assignment was to standard COG low-intensity therapy (including two pegaspargase doses, one each during induction and delayed intensification) with or without four additional pegaspargase doses at 3-week intervals during consolidation and interim maintenance. The study was powered to detect a 4% improvement in 6-year CCR rate from 92% to 96%. RESULTS: The 6-year CCR and overall survival (OS) rates for the entire low-risk cohort were 94.7% ± 0.6% and 98.7% ± 0.3%, respectively. The CCR rates were similar between arms (intensified pegaspargase 95.3% ± 0.8% v standard 94.0% ± 0.8%; P = .13) with no difference in OS (98.1% ± 0.5% v 99.2% ± 0.3%; P = .99). Compared to a subset of standard-risk study patients given identical therapy who had the same early response characteristics but did not have favorable or unfavorable cytogenetics, outcomes were significantly superior for low-risk patients (CCR hazard ratio 1.95; P = .0004; OS hazard ratio 5.42; P < .0001). CONCLUSION: Standard COG therapy without intensified pegaspargase, which can easily be given as an outpatient with limited toxicity, cures nearly all children with B-ALL identified as low-risk by clinical, early response, and favorable cytogenetic criteria.

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.

Pediatric aggressive mature B-cell lymphomas are the most common types of non-Hodgkin lymphoma in children, and they include Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL). These diseases are highly aggressive but curable, the treatment is complex, and patients may have many complicated supportive care issues. The NCCN Guidelines for Pediatric Aggressive Mature B-Cell Lymphomas provide guidance regarding pathology and diagnosis, staging, initial treatment, disease reassessment, surveillance, therapy for relapsed/refractory disease, and supportive care for clinicians who treat sporadic pediatric BL and DLBCL.

Background The BCL-2 inhibitor venetoclax (ven) has revolutionized the treatment of acute myeloid leukemia (AML) in elderly adults, leading to its recent FDA approval for this population in combination regimens. Although extensive data exist for adult myeloid malignancies, there are limited preclinical data on the efficacy and/or dosing of venetoclax for pediatric myelodysplastic syndrome (MDS) or AML and thus little information to guide use of this regimen in pediatric patients. Our objective was to describe our single-center experience with venetoclax in combination with the hypomethylating agent 5-azacitidine (aza) in pediatric patients with MDS or AML. Procedure We conducted a retrospective chart review of patients treated at Children's Hospital Colorado prior to March 2020 with at least one cycle of ven/aza. Patients were included if between the ages of 1 and 25 years with a diagnosis of high-grade MDS or AML. AML patients had relapsed or primary refractory disease or were deemed poor candidates for standard chemotherapy. Results Eight patients received ven/aza, two for high-grade MDS and six for AML. Ven/aza was well tolerated by all patients. The most common adverse events seen with this regimen were gastrointestinal and hematologic. Morphologic responses were seen in six patients including both patients with MDS. All four AML responders became minimal residual disease negative. Three responders have thus far proceeded to allogeneic hematopoietic stem cell transplant following ven/aza. Conclusions Our clinical experience suggests that ven/aza is a safe and promising regimen that should be further explored with late-phase clinical trials.

PURPOSE Asparaginase (ASNase) is an important component of acute lymphoblastic leukemia (ALL) treatment, but is often discontinued because of toxicity. Erwinia chrysanthemi ASNase ( Erwinia) substitution was approved in 2011 for allergic reactions. Erwinia has, however, been intermittently unavailable because of drug supply issues. The impact of Erwinia substitution or complete ASNase discontinuation is unknown. METHODS Patients aged 1-30.99 years in frontline Children’s Oncology Group trials for B-cell acute lymphoblastic leukemia between 2004 and 2011 (National Cancer Institute [NCI] standard risk [SR]: AALL0331; NCI high risk: AALL0232) were included. The number of prescribed pegaspargase (PEG-ASNase) doses varied by trial and strata. Maintenance therapy did not contain ASNase. Landmark analyses at maintenance compared disease-free survival (DFS) among those receiving all prescribed PEG-ASNase doses versus switching to Erwinia but receiving all doses versus not receiving all ASNase doses. RESULTS We included 5,195 AALL0331 and 3,001 AALL0232 patients. The cumulative incidence of PEG-ASNase discontinuation was 12.2% ± 4.6% in AALL0331 and 25.4% ± 0.8% in AALL0232. In multivariable analyses, NCI high-risk patients not receiving all prescribed ASNase doses had inferior DFS (hazard ratio [HR], 1.5; 95% CI, 1.2 to 1.9; P = .002) compared with those receiving all prescribed PEG-ASNase doses. Patients with Erwinia substitution who completed subsequent courses were not at increased risk (HR, 1.1; 95% CI, 0.7 to 1.6; P = .69). NCI SR patients who discontinued ASNase were not at elevated risk (HR, 1.2; 95% CI, 0.9 to 1.6; P = .23), except when restricted to those with slow early response, who were prescribed more ASNase because of therapy intensification (HR, 1.7; 95% CI, 1.1 to 2.7; P = .03). CONCLUSION Discontinuation of ASNase doses is associated with inferior DFS in higher-risk patients. Our results illustrate the severe consequences of Erwinia shortages.

Early response to induction chemotherapy is an important prognostic factor in B-lymphoblastic leukemia (B-ALL). Here, we compare high-throughput sequencing (HTS) of IGH and TRG genes vs flow cytometry (FC) for measurable residual disease (MRD) detection at the end of induction chemotherapy in pediatric patients with newly diagnosed B-ALL. Six hundred nineteen paired pretreatment and end-of-induction bone marrow samples from Children's Oncology Group studies AALL0331 (clinicaltrials.gov #NCT00103285) (standard risk [SR]; with MRD by FC at any level) and AALL0232 (clinicaltrials.gov #NCT00075725) (high risk; with day 29 MRD

Minimal residual disease (MRD) after initial therapy is integral to risk stratification in B-precursor and T-precursor acute lymphoblastic leukemia (B-ALL, T-ALL). Although MRD determines depth of remission, remission remains defined by morphology. We determined the outcomes of children with discordant assessments of remission by morphology vs. flow cytometry using patients age 1-30.99 years enrolled on Children's Oncology Group ALL trials who underwent bone marrow assessment at the end of induction (N = 9350). Morphologic response was assessed locally as M1 (5% lymphoblasts; remission), M2 (5-25%), or M3 (25%). MRD was centrally measured by flow cytometry. Overall, 19.8% of patients with M2/M3 morphology had MRD 5%. M1 with MRD ≥ 5% was less common in B-ALL (0.9%) than T-ALL (6.9%; p 0.0001). In B-ALL, M1/MRD ≥ 5% was associated with superior 5-year event-free survival (EFS) than M2/MRD ≥ 5% (59.1% ± 6.5% vs. 39.1% ± 7.9%; p = 0.009), but was inferior to M1/MRD 5% (87.1% ± 0.4%; p 0.0001). MRD levels were higher in M2/MRD ≥ 5% than M1/MRD ≥ 5% patients. In T-ALL, EFS was not significantly different between M1/MRD ≥ 5% and M2/MRD ≥ 5%. Patients with morphologic remission but MRD ≥ 5% have outcomes similar to those who fail to achieve morphological remission, and significantly inferior to those with M1 marrows and concordant MRD, suggesting that flow cytometry should augment the definition of remission in ALL.

Pediatric Burkitt lymphoma has historically been treated with intensive methotrexate-based chemotherapy, which improves patient survival while causing severe toxicities. Young patients typically have better outcomes with intensive therapies, while adults and immunocompromised patients have higher toxicities and worse outcomes. Newer treatment regimens, including etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, rituximab (EPOCH-R), show promise for these patients. However, few studies exist to demonstrate efficacy and improved toxicity profile with EPOCH-R. We present 2 cases: a 25-year-old male with Down syndrome and an 18-year-old male with Burkitt lymphoma and significant renal injury who were successfully treated with EPOCH-R with minimal toxicities.

Introduction: Health disparities are major issue for racial, ethnic, and socioeconomically disadvantaged groups. Though outcomes in childhood acute lymphoblastic leukemia (ALL) have steadily improved, identifying persistent disparities is critical. Prior studies evaluating ALL outcomes by race or ethnicity have noted narrowing disparities or that residual disparities are secondary to differences in leukemia biology or socioeconomic status (SES). We aimed to identify persistent inequities by race/ethnicity and SES in childhood ALL in the largest cohort ever assembled for this purpose. Methods: We identified a cohort of newly-diagnosed patients with ALL, age 0-30.99 years who were enrolled on COG trials between 2004-2019. Race/ethnicity was categorized as non-Hispanic white vs. Hispanic vs. non-Hispanic Black vs. non-Hispanic Asian vs. Non-Hispanic other. SES was proxied by insurance status: United States (US) Medicaid (public health insurance for low-income individuals) vs. US other (predominantly private insurance) vs. non-US patients (mainly jurisdictions with universal health insurance). Event-free and overall survival (EFS, OS) were compared across race/ethnicity and SES. The relative contribution of disease prognosticators (age, sex, white blood cell count, lineage, central nervous system status, cytogenetics, end Induction minimal residual disease) was examined with Cox proportional hazard multivariable models of different combinations of the three constructs of interest (race/ethnicity, SES, disease prognosticators) and examining hazard ratio (HR) attenuation between models. Results: The study cohort included 24,979 children, adolescents, and young adults with ALL. Non-Hispanic White patients were 13,872 (65.6%) of the cohort, followed by 4,354 (20.6%) Hispanic patients and 1,517 (7.2%) non-Hispanic Black patients. Those insured with US Medicaid were 6,944 (27.8%). Five-year EFS (Table 1) was 87.4%±0.3% among non-Hispanic White patients vs. 82.8%±0.6% [HR 1.37, 95 th confidence interval (95CI) 1.26-1.49; p Table 2 shows the multivariable models and illustrates different patterns of HR adjustment among specific racial/ethnic and SES groups. Inferior EFS among Hispanic patients was substantially attenuated by the addition of disease prognosticators (HR decreased from 1.37 to 1.17) and further (but not fully) attenuated by the subsequent addition of SES (HR 1.11). In contrast, the increased risk among non-Hispanic Black children was minimally attenuated by both the addition of disease prognosticators and subsequent addition of SES (HR 1.45 to 1.38 to 1.32). Similarly, while the superior EFS of non-US insured patients was substantially attenuated by the addition of race/ethnicity and disease prognosticators (HR 0.79 to 0.94), increased risk among US Medicaid patients was minimally attenuated by the addition of race/ethnicity or disease prognosticators (HR 1.21 to 1.16). OS disparities followed similar patterns but were consistently worse than in EFS, particularly among patients grouped as non-Hispanic other. Conclusions: Substantial disparities in survival outcomes persist by race/ethnicity and SES in the modern era. Our findings suggest that reasons for these disparities vary between specific disadvantaged groups. Additional work is required to identify specific drivers of survival disparities that may be mitigated by targeted interventions. Figure 1 Figure 1. Disclosures Gupta: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Teachey: NeoImmune Tech: Research Funding; Sobi: Consultancy; BEAM Therapeutics: Consultancy, Research Funding; Janssen: Consultancy. Zweidler-McKay: ImmunoGen: Current Employment. Loh: MediSix therapeutics: Membership on an entity's Board of Directors or advisory committees.

Contemporary risk stratification algorithms commonly use threshold-defined categories of clinically relevant risk factors. The Children's Oncology Group (COG) uses National Cancer Institute (NCI) risk group (RG), cytogenetics, and early response to therapy measured by minimal residual disease (MRD) using flow cytometry on day 8 peripheral blood (D8 PB) and day 29 bone marrow (D29 BM). However, it is unclear whether assigning different weights to individual risk factors, as well as using numerical values as continuous, rather than categorical, would more accurately predict relapse risk. Previous work (Loh, ASH 2020) described validation of a continuous prognostic index (PI) for risk of relapse published by UK investigators incorporating favorable and unfavorable genetics, white blood cell count (WBC), and D29 BM as continuous variables (O'Connor, JCO 2018; Enshaei, Blood 2020), and assessed the added value of D8 PB. We now extend this work by comparing patient outcomes with current COG risk classification to PI-derived risk classifications on the previously described population (Loh, ASH 2020). We first retrospectively classified patients (pts) (N=21,199 from prior COG trials AALL0331/0232 or AALL0932/1131 enrolled 2004-2019) in our analysis population using the COG risk stratification algorithm employed in the current generation of COG trials. Pts with Down syndrome or BCR/ABL1 were excluded. We classified our analysis population as SR-Favorable [SR-Fav, 24.5% (5-year relapse free survival (RFS) probability 0.97)], SR-Favorable/Average (not distinguishable because of missing D8 PB) [SR-Fav/Avg, 5.3% (.96)], SR-Avg [20.5% (0.93)], SR-High [12.5% (0.83)], HR-Fav [3.0% (0.96)], HR [29.6% (0.82)], and Very HR [VHR, 1.1% (0.54)] according to NCI RG, CNS status, cytogenetics, D8 PB where relevant, D29 BM, and EOC MRD. Ninety-seven percent of pts had sufficient data to be retrospectively classified and thus 20,176 pts were considered for subsequent analyses. We next developed a multivariable model for RFS using log transformed MRD (τ(MRD)). Temporal external validation was first employed by developing models considering AALL0932/1131 data (n=12,453) and then validating them with AALL0331/0232 data (n=7,723). Of the full cohort of 20,176 pts, 24.4% could not be classified by COG PI, primarily due to missing D8 PB MRD which was not assessed routinely in earlier studies; thus the model was developed on 11,151 pts and validated on 4,103 pts. The COG PI (PI COG) was calculated using the equation [τ(d8 MRD) x -0.036 + τ(d29 MRD) x -0.119 + CYTO-GR x -0.914 + CYTO-HR x 0.752 + WBC log x 0.178]. The UK PI (PI UK) was also calculated using published coefficients [τ(d29 MRD) x -0.218 + CYTO-GR x -0.440 + CYTO-HR x 1.066 + WBC log x 0.138] for comparison to assess the practical significance of adding D8 PB. In contrast to the UK method, we identified risk groups by selecting PI cutoffs that maximized the discrimination of the predictive model as quantified by the concordance probability estimator (CPE) (Barrio, SORT 2017). This objective method of cutpoint determination allows for risk group definition without investigator agreement on exact prespecified risk group characteristics; this method also defined four risk groups (Low, Standard, Intermediate, and High). Cutpoints derived from the two different indices, applied to the pts who could be classified by PI COG (n=15,254), resulted in different proportions of pts in each of the risk groups with generally similar RFS estimates for each group. Using cutpoints estimated for PI COG (-2.073, -1.307, and -0.857) 36.0% (RFS = 0.97) were classified as low, 29.6% (0.93) standard, 17.1% (0.88) intermediate, and 17.4% (0.73) high risk of relapse. For PI UK ( -2.916, -2.534, and -1.15), among those who were classifiable by PI COG, 33.4% (0.97) were classified as low, 26.3% (0.93) standard, 30% (0.87) intermediate, and 10.4% (0.69) high. Finally, we compared the COG risk stratification to PI CPE-defined risk stratification in the cohort. As shown in the table, PI COG improves discrimination among individuals by identifying groups with different relapse risk than expected. The PI COG can thus identify patients for whom therapeutic intensification may not result in significantly better outcomes while improving the discrimination of HR pts to allow randomized interventions with achievable hazard ratios. Figure 1 Figure 1. Disclosures Loh: MediSix therapeutics: Membership on an entity's Board of Directors or advisory committees. Borowitz: Amgen, Blueprint Medicines: Honoraria. Zweidler-McKay: ImmunoGen: Current Employment. Mullighan: AbbVie: Research Funding; Amgen: Current equity holder in publicly-traded company; Illumina: Membership on an entity's Board of Directors or advisory committees; Pfizer: Research Funding. Hunger: Amgen: Current equity holder in publicly-traded company. Raetz: Pfizer: Research Funding; Celgene: Other: DSMB member.

Acute lymphoblastic leukemia (ALL) is the most common cancer in childhood. Standard chemotherapy has afforded outstanding outcomes for many patients; however, there remain some sub-groups with high-risk features, refractory disease, and patients that relapse who have a poor prognosis with conventional treatments. Over the past decade, there have been significant advances in newer treatment options, including improved monoclonal antibody therapies, T cell engagers, and chimeric antigen T-cell receptor products, all of which have changed the landscape for patients who relapse. These are now being introduced more frequently and at earlier stages of therapy. We present a brief overview of the biology and etiology of childhood ALL, treatment strategies currently in use, and discuss some newer strategies and their possible role in the future of ALL therapy for children.

PEGylated asparaginase (pegaspargase) can be administered via intramuscular (IM) injection or intravenous (IV) infusion with a hypersensitivity reaction (HSR) incidence ranging 3–41%. We evaluated grade ≥3 HSRs when given IM vs. IV on six Children’s Oncology Group (COG) leukemia trials (2003–2015) to determine differences in HSR rates. 54,280 doses were administered to 16,534 patients. Considering all doses of pegaspargase during induction, consolidation, and delayed intensification, grade ≥3 HSR rate with IM injection was 5.4% (n = 482/8981) compared to 3.2% for IV (n = 245/7553) (p < .0001). If only the second and third doses of pegaspargase were analyzed, where the majority of grade ≥3 HSRs occur, the rate following IM injection was 10.1% (n = 459/4534) compared to 5.0% (n = 222/4443) for IV (p < .0001). On standardized treatment protocols conducted by the COG during 2003–2015, grade ≥3 HSR rates to pegaspargase occurred less frequently with IV infusion than IM injection.

Purpose To determine the prognostic significance of blasts, and of white and red blood cells, in CSF samples at diagnosis of acute lymphoblastic leukemia (ALL), a uniform CSF and risk group classification schema was incorporated into Children’s Oncology Group B-cell ALL (B-ALL) clinical trials. Methods CSF status was designated as follows: CNS1, no blasts; CNS2a to 2c, < 5 WBCs/μL and blasts with/without ≥ 10 RBCs/μL or ≥ 5 WBCs/μL plus blasts, with WBCs ≥ 5 times the number of RBCs; CNS3a to 3c, ≥ 5 WBCs/μL plus blasts with/without ≥ 10 RBCs/μL or clinical signs of CNS disease. CNS2 status did not affect therapy; patients with CNS3 status received two extra intrathecal treatments during induction and augmented postinduction therapy with 18 Gy of cranial radiation. Results Among 8,379 evaluable patients enrolled from 2004 to 2010, 7,395 (88.3%) had CNS1 status; 857 (10.2%), CNS2; and 127 (1.5%), CNS3. The 5-year event-free and overall survival rates were, respectively, 85% and 92.7% for CNS1, 76% and 86.8% for CNS2, and 76% and 82.1% for CNS3 ( P < .001). In multivariable analysis that included age, race/ethnicity, initial WBC, and day-29 minimal residual disease < 0.1%, CSF blast, regardless of cell count, was an independent adverse predictor of outcome for patients with standard- or high-risk disease according to National Cancer Institute criteria. The EFS difference reflected a significant difference in the incidence of CNS, not marrow, relapse in patients with CNS1 versus CNS2 and/or CNS3 status. Conclusion Low levels of CNS leukemia, regardless of RBCs, predict inferior outcome and higher rates of CNS relapse. These data suggest that additional augmentation of CNS-directed therapy is warranted for CNS2 disease.

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

Ectonucleoside triphosphate diphosphohydrolase 1 (NTPDase1) degrades the purines ATP and ADP that are key regulators of inflammation and clotting. We hypothesized that NTPDase1 polymorphisms exist and that they regulate this pathway. We sequenced the ENTPD1 gene (encoding NTPDase1) in 216 subjects then assessed genotypes in 2 cohorts comprising 2213 humans to identify ENTPD1 polymorphisms associated with venous thromboembolism (VTE). The G allele of the intron 1 polymorphism rs3176891 was more common in VTE vs. controls (odds ratio 1.26–1.9); it did not affect RNA splicing, but it was in strong linkage disequilibrium with the G allele of the promoter polymorphism rs3814159, which increased transcriptional activity by 8-fold. Oligonucleotides containing the G allele of this promoter region bound nuclear extracts more avidly. Carriers of rs3176891 G had endothelial cells with increased NTPDase1 activity and protein expression, and had platelets with enhanced aggregation. Thus, the G allele of rs3176891 marks a haplotype associated with increased clotting and platelet aggregation attributable to a promoter variant associated with increased transcription, expression, and activity of NTPDase1. We term this gain-of-function phenotype observed with rs3814159 G “CD39 Denver.”—Maloney, J. P., Branchford, B. R., Brodsky, G. L., Cosmic, M. S., Calabrese, D. W., Aquilante, C. L., Maloney, K. W., Gonzalez, J. R., Zhang, W., Moreau, K. L., Wiggins, K. L., Smith, N. L., Broeckel, U., Di Paola, J. The ENTPD1 promoter polymorphism −860 A > G (rs3814159) is associated with increased gene transcription, protein expression, CD39/NTPDase1 enzymatic activity, and thromboembolism risk.

Current risk stratification for COG ALL patients (pts) relies on National Cancer Institute (NCI) risk group (RG) at diagnosis, somatic genetics, and early response to therapy as measured by specific thresholds of minimal residual disease (MRD) using flow cytometry on day 8 peripheral blood (D8 PB) and day 29 bone marrow (D29 BM). NCI RG is defined as age 1-10 years (yrs) and white blood cell count (WBC) We first log transformed WBC, D8 and D29 MRD and displayed these by treatment protocol, NCI RG, and FRG/URG (separating out Ph-like independently). Age and WBC followed the normal expected distribution with the median age of SR pts 4.0 yrs (range 1-9) and HR 12 yrs (range 1-30). Transformed MRD was displayed as a variable t(MRD), corresponding to the negative log; max t(D29 MRD) was 13.82, corresponding to MRD We next conducted a univariate analysis for risk factors for relapse, including sex, age, WBClog, CNS status, protocol-defined rapid early response status, FRG, URG, t(D8 MRD), and t(D29 MRD); all variables except CNS status were significant p < 0.0001). Multivariable modeling showed that WBClog, FRG, URG, t(D8 MRD), t(D29 MRD) retained significance (p < 0.0001). Finally, we applied the UK Prognostic Index (PIUKALL) equation [t(d29 MRD) x -0.218 + CYTO-GR x -0.440 + CYTO-HR x 1.066 + WBClog x 0.138] to the COG data using protocol, NCI RG, FRG, URG, IRG, or Ph-like RG in the model and validated the trends for relapse-free survival (RFS), which were similar in our groups with an overall median PIUKALL of -2.63 (mean -2.32, SD -.90, min -3.54, max 1.79). We next added in t(D8 MRD) to define a PICOG and determined that D8 PB MRD added significantly to the model, mostly through discriminating between the hazard ratios of the FRG and the URG RGs. Importantly, the D8 PB MRD led to a qualitatively more distinctive group with a potentially lower predicted RFS in NCI SR pts, a group that has been more difficult to predict in the past, and yet comprises nearly half of all relapse events. Our analyses of 21,178 COG B-ALL pts confirm and extend the utility of integrating WBC and MRD as continuous rather than categorical values to refine risk stratification for patient treatment and trial design. Disclosures Loh: Pfizer: Other: Institutional Research Funding; Medisix Therapeutics: Membership on an entity's Board of Directors or advisory committees. Borowitz:Amgen: Honoraria. Zweidler-McKay:ImmunoGen, Inc.: Current Employment. Mattano:Melinta Therapeutics: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Hunger:Amgen: Current equity holder in publicly-traded company, Honoraria; Novartis: Consultancy. Raetz:Celgene/BMS: Other; Pfizer: Research Funding. Mullighan:Illumina: Consultancy, Honoraria, Speakers Bureau; Pfizer: Honoraria, Research Funding, Speakers Bureau; AbbVie, Inc.: Research Funding.

Background: Patients with Down syndrome (DS) have an approximately 10-fold increased risk of developing ALL, and the spectrum of genetic alterations differs from that of non-DS ALL. Rearrangement and/or overexpression of cytokine receptor-like factor 2 (CRLF2+) occurs in 50% of DS ALL, compared to only 5-10% CRLF2+ cases in non-DS children and adolescents. JAK2 or JAK1 mutations co-occur in about half of CRLF2+ cases in both DS and non-DS ALL. The prognostic significance of CRLF2+ ALL also appears to differ in the limited data reported to date, with less adverse impact in patients with DS compared to non-DS ALL. Here, we report the clinical characteristics and prognostic significance of B-ALL with CRLF2 overexpression and JAK alterations in children and adolescents/young adults (AYA) with DS who were treated on Children's Oncology Group (COG) clinical trials from 2003-2016. Methods: We analyzed clinical, laboratory, and outcome data for 317 patients with DS B-ALL treated on standard risk (SR) trials AALL0331 and AALL0932 and high risk (HR) trials AALL0232 and AALL1131, for whom CRLF2 status and rearrangement partners (IGH or P2RY8) were ascertained by flow cytometric assessment of surface expression; fluorescence in situ hybridization; and/or polymerase chain reaction (PCR) testing. JAK mutations were ascertained in a subset by PCR and sequencing. Minimal residual disease (MRD) was assessed by flow cytometry at the end of induction (EOI) and at end of consolidation (EOC) for a subset of EOI MRD+ patients. Results: We identified 168/317 (53.0%) CRLF2+ cases, and among those assessed for CRLF2 partner, 17/73 (23.3%) were IGH-CRLF2 and 56/73 (76.7%) were P2RY8-CRLF2. In the subset of 165 cases tested for JAK mutations (85 CRLF2- and 80 CRLF2+), 42/165 (25.4%) had JAK mutations, all of which co-occurred in CRLF2+ cases. CRLF2 positivity was significantly associated with younger age at diagnosis: 140/168 (83.3%) of CRLF2+ cases were under 10 years old, versus 106/149 (71.1%) of CRLF2- cases, p Discussion: Whereas CRLF2 and JAK alterations are associated with higher MRD, poorer survival, and increased CIR in patients with high-risk ALL without DS, these alterations do not demonstrate strong adverse prognostic impact in children and AYAs with DS-ALL treated on recent frontline COG trials, although larger sample sizes are needed to adequately assess for possible poorer prognoses associated with the CRLF2+/JAK+ and IGH-CRLF2 subgroups. Regardless, given the frequency of these targetable lesions and the increased risk of relapse and chemotherapy-associated toxicities in patients with DS-ALL, targeted therapies currently under investigation for these genetic lesions may be beneficial to replace some intensive blocks of therapy in DS-ALL with CRLF2 and/or JAK alterations, both to enhance anti-leukemic efficacy and decrease intensive chemotherapy-associated toxicities. Figure 1 Disclosures Tasian: Gilead Sciences: Research Funding; Incyte Corporation: Research Funding; Aleta Biotherapeutics: Membership on an entity's Board of Directors or advisory committees. Borowitz:Amgen: Honoraria. Mullighan:Illumina: Consultancy, Honoraria, Speakers Bureau; AbbVie, Inc.: Research Funding; Pfizer: Honoraria, Research Funding, Speakers Bureau. Raetz:Celgene: Other: DSMB member; Pfizer: Other: Institutional research funding. Loh:Pfizer: Other: Institutional Research Funding; Medisix Therapeutics: Membership on an entity's Board of Directors or advisory committees. Hunger:Novartis: Consultancy; Amgen: Current equity holder in publicly-traded company, Honoraria.

BACKGROUND: Survival for children with B and T acute lymphoblastic leukemia (B-ALL, T-ALL) has continued to improve. In past cohorts, boys experienced inferior survival outcomes compared to girls. Though reasons are unknown, previous investigators have suggested that these disparities are explained by imbalances in risk factors, such as a higher proportion of T-ALL among boys. We thus examined whether sex-based disparities persist with modern intensive therapy when adjusted for other risk factors. We also determined if patterns of toxicity and treatment failure varied by sex. METHODS: We identified a cohort of patients age 1-30.99 years enrolled on frontline COG trials for B-ALL (standard risk: AALL0331; high risk: AALL0232) and T-ALL (AALL0434) between 2004-2014. Duration of treatment was sex-dependent, with boys receiving an additional year of Maintenance therapy. A limited number of B-ALL patients (those with slow early response or CNS3 status) underwent cranial radiation, while all intermediate and standard risk T-ALL patients did so. Sex-based differences in the distribution of various prognostic factors were explored, including age at diagnosis, initial white blood cell (WBC) count, central nervous system (CNS) status, leukemia cytogenetics, and end Induction minimal residual disease (MRD). Event-free and overall survival (EFS, OS) were compared between boys and girls using log-rank tests and multivariable Cox regression analyses. Finally, we explored sex-based differences in toxicity rates and in the cumulative incidence of specific causes of treatment failure, including treatment-related mortality (TRM), overall relapse, and subcategories of relapse by site. RESULTS: The study cohort included 8,202 patients with B-ALL [4,463 (54.4%) boys] and 1,562 patients with T-ALL [1,161 (74.3%) boys]. Among B-ALL patients, boys were older than girls and slightly more likely to have unfavorable cytogenetics (Table 1). There was no difference in the distribution of initial WBC or CNS status. Among T-ALL patients, boys were again older than girls, but other prognostic factors did not differ by sex (Table 1). B-ALL boys were less likely to be end induction marrow MRD < 0.01% [3,268 (76.1%) vs. 2791 (78.1%); p=0.04] while T-ALL boys were more likely to achieve end induction MRD < 0.01% [659 (59.0%) vs. 221 (56.8%); p=0.01], although in both cases absolute differences were small. EFS and OS were inferior in B-ALL boys compared to girls (5-year: EFS 84.6%±0.6% vs. 86.4%±0.6%; p=0.003; OS 91.7%±0.4% vs. 92.8%±0.5%; p=0.046). The risk of inferior outcomes among B-ALL boys persisted after adjustment for other prognostic factors in both EFS [hazard ratio (HR) 1.18, 95% confidence interval (1.05-1.33); p=0.003] and OS (HR 1.17 (1.00-1.37); p=0.048). There were no sex-based differences in EFS or OS in T-ALL. When examining specific toxicities and causes of treatment failure, osteonecrosis rates were lower among boys [297/5,624 (5.3%) vs. 281/4,140 (6.8%); p=0.002]. The incidence of TRM did not differ by sex. The incidence of relapse was, however, greater in boys than girls with B-ALL (11.2%±0.5% vs. 9.6%±0.5%; p=0.001). This risk was attributable to a higher incidence of relapses involving the CNS (4.2%±0.3% vs. 2.5%±0.3%; p CONCLUSIONS: Small sex-based disparities in ALL outcomes persist despite overall improvements, extended treatment duration, and extra intrathecal therapy in boys. This is mainly attributable to a higher risk of CNS relapse in boys with B-ALL, despite no sex-based differences in initial CNS status, and persists when adjusted for other prognostic risk factors. The lack of sex-based disparities in T-ALL by sex may be in part due to an increased use of CNS radiation, given older studies which observed increases in CNS relapse rates among boys but not girls when radiation was eliminated. Future studies to determine the mechanisms underlying this disparity, including potential sex-based differences in steroid metabolism, are warranted. Disclosures Teachey: Amgen: Consultancy; Sobi: Consultancy; Janssen: Consultancy; La Roche: Consultancy. Dunsmore:Dexcom: Current equity holder in publicly-traded company. Mattano:Melinta Therapeutics: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Borowitz:Amgen: Honoraria. Raetz:Pfizer: Research Funding; Celgene/BMS: Other. Loh:Pfizer: Other: Institutional Research Funding; Medisix Therapeutics: Membership on an entity's Board of Directors or advisory committees. Hunger:Novartis: Consultancy; Amgen Inc.: Current equity holder in publicly-traded company, Honoraria.

Background: Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) occurs in 5-30% of children and adolescents/young adults (AYAs) with B-ALL, is driven by genetic alterations that induce constitutive cytokine receptor and kinase signaling, and is associated with poor clinical outcomes across the older pediatric-to-adult age spectrum (Tasian Blood 2017c, Reshmi Blood 2017, Roberts Blood 2018). Rearrangement and/or overexpression of cytokine receptor-like factor 2 (CRLF2+) occurs in 50% of Ph-like ALL cases with frequently co-occurring JAK2 or JAK1 point mutations or IL7R indel mutations. This study reports the clinical outcomes of children and AYAs with newly-diagnosed National Cancer Institute (NCI) standard-risk (SR) or high-risk (HR) CRLF2+ ALL without Down syndrome treated on four successive Children's Oncology Group (COG) phase 3 clinical trials from 2003 to 2018. Methods: We retrospectively assessed demographic characteristics, laboratory data, and clinical outcomes of 3757 patients with B-ALL treated on COG trials AALL0331 and AALL0932 (SR) and AALL0232 and AALL1131 (HR) whose diagnostic leukemia specimens were analysed by low-density microarray (LDA), fluorescence in situ hybridization, polymerase chain reaction (PCR), and/or anchored multiplex PCR testing (Harvey and Tasian Blood Advances 2020). Minimal residual disease (MRD) was assessed by flow cytometry at the end of induction (EOI) and at the end of consolidation for a subset of EOI MRD+ patients. Results: We identified 77/1541 (5.0%) SR and 244/2216 (11.0%) HR patients with CRLF2+ B-ALL in this cohort. Amongst those with diagnostic leukemia specimens analysed by LDA, 57/72 (79.2%) of SR CRLF2+ and 175/213 (82.2%) of HR CRLF2+ patients were positive for the Ph-like gene expression profile with an 8-gene score ≥0.5. P2RY8-CRLF2 fusions and IGH-CRLF2 translocations were detected in 64/77 (83.1%) and 10/77 (13.0%) of SR CRLF2+ patients and in 98/244 (40.2%) and 103/244 (42.2%) of HR CRLF2+ patients, respectively. CRLF2 rearrangements or F232C mutations were not found in the remaining 3 SR and 43 HR CRLF2+ patients, although other Ph-like alterations were discovered in some (n=3 IGH-EPOR fusions, 1 IL7R indel). Importantly, CRLF2+ vs non-CRLF2-overexpressing (CRLF2-) status was associated with older age (10.8 ±6.5 vs 7.8 ±5.8 years [mean ±SD], p Discussion: Patients with newly-diagnosed CRLF2+ B-ALL treated on frontline COG trials have higher rates of EOI MRD positivity, inferior survival, and increased CIR compared to their CRLF2- counterparts. EFS is especially poor in children and AYAs with NCI HR CRLF2+ ALL, particularly those with the Ph-like expression profile. Conversely, outcomes for children with NCI SR CRLF2+ ALL are reasonably favourable, irrespective of Ph-like status. Development of successful treatment strategies to decrease relapse and to improve survival remains a major therapeutic gap for NCI HR CRLF2+ ALL patients. Current clinical trials are studying the potential efficacy of kinase inhibitor addition to chemotherapy for children, adolescents, and adults with HR Ph-like ALL harboring CRLF2 rearrangements/other JAK pathway alterations or ABL class kinase fusions (NCT0240717, NCT02723994, NCT02883049, NCT03571321). Figure 1 Disclosures Tasian: Gilead Sciences: Research Funding; Incyte Corporation: Research Funding; Aleta Biotherapeutics: Membership on an entity's Board of Directors or advisory committees. Borowitz:Amgen: Honoraria. Mullighan:AbbVie, Inc.: Research Funding; Illumina: Consultancy, Honoraria, Speakers Bureau; Pfizer: Honoraria, Research Funding, Speakers Bureau. Hunger:Novartis: Consultancy; Amgen: Current equity holder in publicly-traded company, Honoraria. Raetz:Pfizer: Research Funding; Celgene/BMS: Other. Loh:Pfizer: Other: Institutional Research Funding; Medisix Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Hyperdiploidy with greater than 50 chromosomes is usually associated with favorable prognosis in pediatric acute lymphoblastic leukemia (ALL), whereas hypodiploidy with ≤43 chromosomes is associated with extremely poor prognosis. Sometimes, hypodiploidy is "masked" and patients do not have a karyotypically visible clone with ≤43 chromosomes. Instead, their abnormal karyotypes contain 50-78 or more chromosomes from doubling of previously hypodiploid cells. When the hypodiploid and doubled hyperdiploid clones are both present, patients can be identified by traditional test methods [karyotype, DNA Index (DI), fluorescence in situ hybridization (FISH)], but the incidence of masked hypodiploid cases in which only the doubled clone is visible is unknown. We analyzed 7013 patients with B-ALL enrolled in COG AALL03B1 (2003-2011) for whom chromosome studies were available. Of 115 patients with hypodiploidy (25-39 chromosomes), karyotypes of 40 showed only the hypodiploid clone, 47 showed mosaicism with both hypodiploid and hyperdiploid (doubled) karyotypes, and 28 with masked hypodiploidy showed only a hyperdiploid (doubled) clone. Unique karyotypic signatures were identified, and widespread loss of heterozygosity (LOH) was seen in the microsatellite panel for all patients with masked hypodiploidy. An increased awareness of the unusual karyotypic profile associated with a doubled hypodiploid clone and coordinated use of DI, FISH, and LOH studies when indicated can identify patients with masked hypodiploidy and allow appropriate treatment selection.

Purpose Children and young adults with hypodiploid B-lymphoblastic leukemia (B-ALL) fare poorly and hematopoietic stem-cell transplantation (HSCT) is often pursued in first complete remission (CR1). We retrospectively reviewed the outcomes of children and young adults with hypodiploid B-ALL who were enrolled in recent Children’s Oncology Group (COG) trials to evaluate the impact of HSCT on outcome. Patients and Methods Cytogenetic analyses and DNA index were performed at COG-approved laboratories, and hypodiploidy was defined as modal chromosome number less than 44 and/or DNA index less than 0.81. Minimal residual disease (MRD) was determined centrally using flow cytometry at two reference laboratories. Patients with hypodiploid ALL came off protocol therapy postinduction and we retrospectively collected details on their subsequent therapy and outcomes. Event-free survival (EFS) and overall survival (OS) were estimated for the cohort. Results Between 2003 and 2011, 8,522 patients with National Cancer Institute standard-risk and high-risk B-ALL were enrolled in COG AALL03B1 ( ClinicalTrials.gov identifier: NCT00482352). Hypodiploidy occurred in 1.5% of patients (n = 131), 98.3% of whom achieved CR after induction therapy. Five-year EFS and OS were 52.2% ± 4.9% and 58.9% ± 4.8%, respectively. Outcomes for patients undergoing CR1 HSCT were not significantly improved: 5-year EFS and OS were 57.4% ± 7.0% and 66.2% ± 6.6% compared with 47.8% ± 7.5% and 53.8% ± 7.6%, respectively ( P = .49 and .34, respectively) for those who did not undergo transplantation. Patients with MRD of 0.01% or greater at the end of induction had 5-year EFS and OS of 26.7% ± 9.3% and 29.3% ± 10.1%, respectively, and HSCT had no significant impact on outcomes. Conclusion Children and young adults with hypodiploid B-ALL continue to fare poorly and do not seem to benefit from CR1 HSCT. This is especially true for patients with MRD of 0.01% or greater at the end of induction. New treatment strategies are urgently needed for these patients.

BACKGROUND The months immediately after the completion of treatment for childhood acute lymphoblastic leukemia (ALL) are often regarded as a stressful time for children and families. In this prospective, longitudinal study, the prevalence and predictors of anxiety and depressive symptoms after the completion of treatment were examined. METHODS Participants included 160 children aged 2 to 9 years with standard-risk ALL who were enrolled on Children's Oncology Group protocol AALL0331. Parents completed standardized rating scales of their children's emotional-behavioral functioning and measures of coping and family functioning at approximately 1 month, 6 months, and 12 months after diagnosis and again 3 months after the completion of chemotherapy. RESULTS At 3 months off therapy, approximately 24% of survivors had at-risk/clinically elevated anxiety scores and 28% had elevated depression scores, which are significantly higher than the expected 15% in the general population (P = .028 and .001, respectively). Patients with elevated anxiety 1 month after diagnosis were at greater risk of off-therapy anxiety (odds ratio, 4.1; 95% confidence interval, 1.31-12.73 [P = .022]) and those with elevated depressive symptoms 6 months after diagnosis were at greater risk of off-therapy depression (odds ratio, 7.88; 95% confidence interval, 2.61-23.81 [P = .0002]). In adjusted longitudinal analyses, unhealthy family functioning (P = .008) and less reliance on social support coping (P = .009) were found to be associated with risk of emotional distress. Children from Spanish-speaking families (P = .05) also were found to be at a greater risk of distress. CONCLUSIONS A significant percentage of children experience emotional distress during and after therapy for ALL. These data provide a compelling rationale for targeted early screening and psychosocial interventions to support family functioning and coping skills. Cancer 2016;122:1608–17. © 2015 American Cancer Society.

BACKGROUND This prospective study describes the procedure-related anxiety, treatment-related anxiety, pain, and nausea experienced by children with standard-risk acute lymphoblastic leukemia (ALL) during the first year of treatment. METHODS This study was undertaken at 31 Children's Oncology Group (COG) sites. Eligible children who were 2 to 9.99 years old were enrolled in a COG trial for patients with newly diagnosed standard-risk ALL from 2005 to 2009. Parents completed a demographic survey at the baseline and the Pediatric Quality of Life Inventory 3.0 Cancer Module (proxy version) and the General Functioning Scale of the Family Assessment Device 1, 6, and 12 months after the diagnosis. The association between patient-related (age, sex, ethnicity, and treatment), parent-related (marital status and education), and family-related factors (functioning, income, and size) and symptom scores was evaluated. RESULTS The mean scores for procedure-related anxiety, treatment-related anxiety, and pain improved during the first year of treatment (P < .0389). The mean nausea score was poorer 6 months after the diagnosis in comparison with the other assessments (P = .0085). A younger age at diagnosis was associated with significantly worse procedure-related anxiety (P = .004). An older age (P = .0002) and assignment to the intensified consolidation study arm (P = .02) were associated with significantly worse nausea. CONCLUSIONS Children with ALL experienced decreasing treatment-related anxiety, procedure-related anxiety, and pain during the first year of treatment. In comparison with scores at 1 and 12 months, nausea was worse 6 months after the diagnosis. Minimization of procedure-related anxiety in younger children and improved nausea control in older children and those receiving more intensified treatment should be prioritized. Cancer 2016. © 2016 American Cancer Society.

10510 Background: Patients with DS and B-ALL experience increased rates of relapse and toxicities. Here, we report results from 4 COG trials (2003-2018). Methods: We analyzed clinical, and outcome data for DS (n = 743) and non-DS (n = 21,703) patients age 1-30 enrolled on standard-risk (SR) trials AALL0331 and AALL0932 and high-risk (HR) trials AALL0232 and AALL1131. Initially, DS-ALL patients on AALL0232/AALL0331 experienced excess mortality, prompting enhanced supportive care and omission of induction anthracycline except for slow responders on AALL1131. Other modifications included: non-random assignment to treatment strata without investigational agents; leucovorin rescue after intrathecal methotrexate (MTX); equal maintenance length for boys and girls; every 12-week maintenance vincristine/steroid pulses; and reduced anthracycline and intravenous MTX for HR patients. Results: Across all 4 trials, DS and non-DS patients did not differ significantly in age, sex, initial WBC, or CNS status. DS-ALL patients had significantly higher end of induction (EOI) minimal residual disease (MRD) vs non-DS patients on both AALL0932 and AALL1131, but the difference persisted at end of consolidation (EOC) only on AALL1131, with fewer EOI MRD+ DS patients achieving EOC MRD < 0.01% (76.1 vs 88.0%, p = 0.001). 5-year EFS and OS were significantly poorer for DS vs non-DS across all trials (EFS 79.6+2.1% vs 86.3+0.3%, p < 0.0001; OS 86.5+1.8% vs 93.1+0.2%, p < 0.0001), as well as on each individual trial. In Cox regression analysis for all DS patients, inferior EFS was associated with several known risk factors (age > 10, EOI MRD >0.01%) but not with cytogenetics or CRLF2 status Induction death was more frequent in DS patients (3.4% vs 0.8%, p < 0.0001) as was death in remission (4.8+0.8% vs 1.8+0.1%, p < 0.0001). For death in remission, the increased frequency occurred pre-maintenance and in patients taken off protocol therapy, but not during maintenance, in contrast to prior reports. Grade >3 mucositis, infections, and hyperglycemia were significantly more frequent in DS patients on all trials. Grade >3 seizures were significantly more frequent in DS patients on HR but not SR trials (4.1% vs 1.7%. p = 0.001) and occurred in all phases pre-maintenance. Conclusions: Patients with DS and B-ALL continue to have inferior outcomes compared to non-DS, with increased relapse and toxicities. Less toxic approaches such as immunotherapies and targeted therapies hold promise to improve outcomes in both these areas.

10509 Background: Post-hoc analysis of COG P9904 identified a low risk (LR) group of SR B-ALL patients aged 1-9.99 years with WBC < 50,000/µL, no CNS3, and either ETV6/RUNX1 or double trisomies (DT) of chromosomes 4 and 10 with day 8 peripheral blood (PB) and day 29 marrow (BM) minimal residual disease (MRD) < 0.01% who had a 5-year event-free survival (EFS) of 97±2% and overall survival (OS) 98.8±0.8%. Outstanding results were also obtained for LR patients on COG AALL0331 using CCG-based ALL therapy. AALL0932 tested prospectively whether LR B-ALL patients could attain a 5-year EFS ≥95% with these regimens. Methods: Following a 3-drug induction, eligible AALL0932 LR patients had NCI SR B-ALL (no testicular leukemia, unfavorable genetics or Down syndrome) with DT or ETV6/RUNX1 fusion, CNS1, no steroid pre-treatment, with Day 8 PB and Day 29 BM MRD < 0.01%. Between 2010-16, 603 LR patients were randomized to P9904-based regimen LR-M (n = 301) or CCG 1991/COG AALL0331-based regimen LR-C (n = 302). LR-M included 6 24-hour infusions of 1 gm/m2 of methotrexate (MTX) with leucovorin rescue, but no anthracyclines or alkylating agents. Maintenance followed with daily 6-mercaptopurine (6-MP) and weekly oral MTX, and every 16 week 7-day pulses of dexamethasone (DEX) with vincristine (VCR) on days 1 and 8. Boys and girls were treated for 2.5 years from diagnosis. LR-C had no 24-hour MTX infusions, but included 2 Interim Maintenance (IM) phases with VCR and escalating IV MTX without leucovorin rescue given every 10 days for 5 doses, flanking an 8-week Delayed Intensification (DI) phase that included DEX, VCR, pegasparagase, doxorubicin (75 mg/m2), cyclophosphamide (1 gm/m2) and 8 doses of low-dose cytarabine (75 mg/m2/dose). LR-C Maintenance included daily 6-MP and weekly oral MTX with 5-day pulses of DEX and 1 dose of VCR given every 12 weeks. Girls received 2 years and boys 3 years of therapy from the start of IM I. Results: Both regimens achieved outstanding outcomes: 5-yr disease-free survival (±SE) 98.8%±0.8% for LR-M and 98.5%±0.9% for LR-C (p = 0.67). Both had 5-yr OS 100%. Therapies were well tolerated with higher rates of mucositis (12.9 vs 6.3%; p = 0.008) and allergic reactions (2.3% vs 0%; p = 0.02) on LR-C. Conclusions: AALL0932 demonstrated that application of stringent risk criteria can identify a favorable B-ALL subgroup almost certain to be cured with either LR-M or LR-C, allowing physicians and families to select the optimal treatment approach in the future. Clinical trial information: NCT01190930.

Key Points Children treated with blinatumomab for B-ALL with MRD had few side effects and proceeded to hematopoietic cell transplant without delay. Blinatumomab given prior to transplant reduces MRD and results in favorable leukemia-free survival, toxicity, and overall survival.

Recent genomic studies have identified chromosomal rearrangements defining new subtypes of B-progenitor acute lymphoblastic leukemia (B-ALL), however many cases lack a known initiating genetic alteration. Using integrated genomic analysis of 1,988 childhood and adult cases, we describe a revised taxonomy of B-ALL, incorporating 23 subtypes defined by chromosomal rearrangements, sequence mutations, or heterogeneous genomic alterations, many of which show marked variation in prevalence according to age. Two subtypes have frequent alterations of the B lymphoid transcription factor gene PAX5. One, PAX5alt (7.4%), has diverse PAX5 alterations (rearrangements, intragenic amplifications or mutations), and a second subtype is defined by PAX5 p.Pro80Arg and biallelic PAX5 alterations. We show that p.Pro80Arg impairs B lymphoid development and promotes the development of B-ALL with biallelic Pax5 alteration in vivo. These results demonstrate the utility of transcriptome sequencing to classify B-ALL and reinforce the central role of PAX5 as a checkpoint in B lymphoid maturation and leukemogenesis.

Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL; BCR-ABL1-like ALL) in children with National Cancer Institute (NCI) intermediate- or high-risk (HR) ALL is associated with poor outcome. Ph-like ALL is characterized by genetic alterations that activate cytokine receptor and kinase signaling and may be amenable to treatment with tyrosine kinase inhibitors. The prevalence, outcome, and potential for targeted therapy of Ph-like ALL in standard-risk (SR) ALL is less clear. We retrospectively analyzed a cohort of 1023 SR childhood B-ALL consecutively enrolled in the Children's Oncology Group AALL0331 clinical trial. The Ph-like ALL gene expression profile was identified in 206 patients, and 67 patients with either BCR-ABL1 (n = 6) or ETV6-RUNX1 (n = 61) were excluded from downstream analysis, leaving 139 of 1023 (13.6%) as Ph-like. Targeted reverse transcription polymerase chain reaction assays and RNA-sequencing identified kinase-activating alterations in 38.8% of SR Ph-like cases, including CRLF2 rearrangements (29.5% of Ph-like), ABL-class fusions (1.4%), JAK2 fusions (1.4%), an NTRK3 fusion (0.7%), and other sequence mutations (IL7R, KRAS, NRAS; 5.6%). Patients with Ph-like ALL had inferior 7-year event-free survival compared with non-Ph-like ALL (82.4 ± 3.6% vs 90.7 ± 1.0%, P = .0022), with no difference in overall survival (93.2 ± 2.4% vs 95.8 ± 0.7%, P = .14). These findings illustrate the significant differences in the spectrum of kinase alterations and clinical outcome of Ph-like ALL based on presenting clinical features and establish that genomic alterations potentially targetable with approved kinase inhibitors are less frequent in SR than in HR ALL.

Background Erwinia asparaginase is antigenically distinct from E.coli‐derived asparaginase and may be used after E.coli‐derived asparaginase hypersensitivity. In a single‐arm, multicenter study, we evaluated nadir serum asparaginase activity (NSAA) and toxicity with intravenously administered asparaginase Erwinia chrysanthemi (IV‐Erwinia) in children and adolescents with acute lymphoblastic leukemia (ALL) or lymphoblastic lymphoma with hypersensitivity to E.coli‐derived asparaginase. Patients and Methods Between 2012 and 2013, 30 patients (age 1–17 years) enrolled from 10 centers. Patients received IV‐Erwinia, 25,000 IU/m2/dose on Monday/Wednesday/Friday, for 2 consecutive‐weeks (6 doses = 1 cycle) for each dose of pegaspargase remaining in the original treatment plan. The primary objective was to determine the proportion of patients achieving NSAA ≥0.1 IU/ml 48 hr after dose 5 in Cycle 1. Secondary objectives included determining the proportion achieving NSAA ≥0.1 IU/ml 72 hr after Cycle 1 dose 6, and the frequency of asparaginase‐related toxicities. Results Twenty‐six patients completed Cycle 1; 24 were evaluable for NSAA assessment. In Cycle 1, NSAA ≥0.10 IU/ml was detected in 83% of patients (95% confidence interval [CI], 63–95%) 48 hr post‐dose 5 (mean ± SD; 0.32 IU/ml ± 0.23), and in 43% (95% CI, 22–66%) 72 hr post‐dose 6 (mean ± SD; 0.089 IU/ml ± 0.072). For all 30 patients over all cycles, hypersensitivity/infusional reactions with IV‐Erwinia occurred in 37%, pancreatitis 7%, and thrombosis 3%. Conclusions IV‐Erwinia administration in children/adolescents appeared feasible and tolerable. A therapeutically‐effective NSAA (≥0.10 IU/ml) was achieved in most patients at 48 hr, but in fewer than half 72 hr post‐dosing, suggesting that monitoring NSAA levels and/or every 48 hr dosing may be indicated. Pediatr Blood Cancer 2015. © 2015 Wiley Periodicals, Inc.

Standard risk acute lymphoblastic leukemia (SR-ALL) has high cure rates, but requires 2-3 years of therapy. We aimed to (i) prospectively evaluate health-related quality of life (HRQOL) during and after SR-ALL therapy, and (ii) identify associated predictors. Parents of 160 SR-ALL patients enrolled on Children's Oncology Group (COG) therapeutic trial AALL0331 at 31 sites completed the Pediatric Quality of Life Inventory (PedsQL) 4.0 Generic Core Scales (physical, emotional and social functioning) and Family Assessment Device-General Functioning (FAD-GF) at 1, 6 and 12 months after diagnosis, and 3 months post-therapy. Mean PedsQL scores in physical, emotional and social functioning were impaired 1 month after diagnosis but steadily improved. Three months post-therapy, impaired physical and social functioning was observed in 27.8 and 25.8% of patients, respectively. In repeated-measures analysis, problematic family functioning predicted emotional (OR = 1.85, 95% CI 1.03-3.34) and social (OR = 1.99, 95% CI 1.21-3.27) impairment. Larger household size was associated with social impairment (OR = 1.21, 95% CI 1.02-1.45). Adverse neurological event(s) during therapy predicted post-therapy physical (OR = 5.17, 95% CI 1.61-16.63) and social (OR = 8.17, 95% CI 1.19-56.16) impairment. HRQOL 1 month after diagnosis was not predictive of HRQOL 3 months after therapy completion. In conclusion, children with SR-ALL experience considerable impairment in HRQOL at the end of induction, but rapidly improve. However, many still experience physical and social impairment 3 months post-therapy, suggesting a role for continued family and physical functioning support. Longer follow-up is needed to determine if post-therapy deficits change over time.

The clinical characteristics of chronic myeloid leukemia (CML) in lymphoid blast crisis (BC) can resemble those of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph ALL). Because of this, there can be concern as to whether a patient with newly diagnosed Ph leukemia has Ph ALL or CML in lymphoid BC. This distinction has significant potential therapeutic implications because most children with Ph ALL are now treated with chemotherapy plus a tyrosine kinase inhibitor, whereas allogeneic stem cell transplant is usually recommended for any patient with CML that presents in or later develops BC.