Epigenomic mapping in B-cell acute lymphoblastic leukemia identifies transcriptional regulators and noncoding variants promoting distinct chromatin architectures

B-cell lineage acute lymphoblastic leukemia (B-ALL) is comprised of diverse molecular subtypes and while transcriptional and DNA methylation profiling of B-ALL subtypes has been extensively examined, the accompanying chromatin landscape is not well characterized for many subtypes. We therefore mapped chromatin accessibility using ATAC-seq for 10 B-ALL molecular subtypes in primary ALL cells from 154 patients. Comparisons with B-cell progenitors identified candidate B-ALL cell-of-origin and AP-1-associated cis-regulatory rewiring in B-ALL. Cis-regulatory rewiring promoted B-ALL-specific gene regulatory networks impacting oncogenic signaling pathways that perturb normal B-cell development. We also identified that over 20% of B-ALL accessible chromatin sites exhibit strong subtype enrichment, with transcription factor (TF) footprint profiling identifying candidate TFs that maintain subtype-specific chromatin architectures. Over 9000 inherited genetic variants were further uncovered that contribute to variability in chromatin accessibility among individual patient samples. Overall, our data suggest that distinct chromatin architectures are driven by diverse TFs and inherited genetic variants which promote unique gene regulatory networks that contribute to transcriptional differences among B-ALL subtypes.

Clinical characteristics and outcomes of children with newly diagnosed acute myeloid leukemia and hyperleukocytosis managed with different cytoreductive methods

BACKGROUND

Hyperleukocytosis in patients with acute myeloid leukemia (AML) has been associated with worse outcomes. For cytoreduction, leukapheresis has been used but its clinical utility is unknown, and low-dose cytarabine (LD-cytarabine) is used as an alternative method.

METHODS

Children with newly diagnosed AML treated between 1997 and 2017 in institutional protocols were studied. Hyperleukocytosis was defined as a leukocyte count of ≥100 × 109 /L at diagnosis. Clinical characteristics, early complications, survival data, and effects of cytoreductive methods were reviewed. Among 324 children with newly diagnosed AML, 49 (15.1%) presented with hyperleukocytosis. Initial management of hyperleukocytosis included leukapheresis or exchange transfusion (n = 16, considered as one group), LD-cytarabine (n = 18), hydroxyurea (n = 1), and no leukoreduction (n = 14).

RESULTS

Compared with patients who received leukapheresis, the percentage decrease in leukocyte counts following intervention was greater among those who received LD-cytarabine (48% vs. 75%; p = .02), with longer median time from diagnosis to initiation of protocol therapy (28.1 vs. 95.2 hours; p < .001). The incidence of infection was higher in patients (38%) who had leukapheresis than those who receive LD-cytarabine (0%) or leukoreduction with protocol therapy (14%) (p = .008). No differences were noted in the outcomes among the intervention groups. Although patients with hyperleukocytosis had higher incidences of pulmonary and metabolic complications than did those without, no early deaths occurred, and the complete remission, event-free survival, overall survival rates, and outcomes of both groups were similar.

CONCLUSION

LD-cytarabine treatment appears to be a safe and effective means of cytoreduction for children with AML and hyperleukocytosis.

Clinical Impact of Minimal Residual Disease in Blood and Bone Marrow of Children with Acute Myeloid Leukemia

The prognostic significance of bone marrow minimal residual disease (MRD) in pediatric patients with acute myeloid leukemia (AML) is well-characterized, but the impact of blood MRD is not known. We therefore used flow-cytometric assessment of leukemia-specific immunophenotypes to measure levels of MRD in both blood and bone marrow of patients treated on the AML08 (NCT00703820) clinical trial. Blood samples were obtained at days 8 and 22 of therapy, whereas bone marrow samples were obtained at day 22. Among patients who were MRD-negative in the bone marrow at day 22, neither day 8 nor day 22 blood MRD was significantly associated with outcome. However, day 8 blood MRD was highly predictive of outcome among patients who were bone marrow MRD-positive at day 22. Although the measurement of blood MRD at day 8 cannot be used to detect day 22 bone marrow MRD-negative patients who are likely to relapse, our findings suggest that day 8 blood MRD can identify bone marrow MRD-positive patients who have a dismal prognosis and who may be candidates for the early use of experimental therapy.

EBV-driven lymphoid neoplasms associated with pediatric ALL maintenance therapy

The development of a second malignancy after the diagnosis of childhood acute lymphoblastic leukemia (ALL) is a rare event. Certain second malignancies have been linked with specific elements of leukemia therapy, yet the etiology of most second neoplasms remains obscure and their optimal management strategies are unclear. This is a first comprehensive report of non-Hodgkin lymphomas (NHLs) following pediatric ALL therapy, excluding stem-cell transplantation. We analyzed data of patients who developed NHL following ALL diagnosis and were enrolled in 12 collaborative pediatric ALL trials between 1980-2018. Eighty-five patients developed NHL, with mature B-cell lymphoproliferations as the dominant subtype (56 of 85 cases). Forty-six of these 56 cases (82%) occurred during or within 6 months of maintenance therapy. The majority exhibited histopathological characteristics associated with immunodeficiency (65%), predominantly evidence of Epstein-Barr virus-driven lymphoproliferation. We investigated 66 cases of post-ALL immunodeficiency-associated lymphoid neoplasms, 52 from our study and 14 additional cases from a literature search. With a median follow-up of 4.9 years, the 5-year overall survival for the 66 patients with immunodeficiency-associated lymphoid neoplasms was 67.4% (95% confidence interval [CI], 56-81). Five-year cumulative risks of lymphoid neoplasm- and leukemia-related mortality were 20% (95% CI, 10.2-30) and 12.4% (95% CI, 2.7-22), respectively. Concurrent hemophagocytic lymphohistiocytosis was associated with increased mortality (hazard ratio, 7.32; 95% CI, 1.62-32.98; P = .01). A large proportion of post-ALL lymphoid neoplasms are associated with an immunodeficient state, likely precipitated by ALL maintenance therapy. Awareness of this underrecognized entity and pertinent diagnostic tests are crucial for early diagnosis and optimal therapy.

Proteasome inhibition targets the KMT2A transcriptional complex in acute lymphoblastic leukemia

Rearrangments in Histone-lysine-N-methyltransferase 2A (KMT2Ar) are associated with pediatric, adult and therapy-induced acute leukemias. Infants with KMT2Ar acute lymphoblastic leukemia (ALL) have a poor prognosis with an event-free-survival of 38%. Herein we evaluate 1116 FDA approved compounds in primary KMT2Ar infant ALL specimens and identify a sensitivity to proteasome inhibition. Upon exposure to this class of agents, cells demonstrate a depletion of histone H2B monoubiquitination (H2Bub1) and histone H3 lysine 79 dimethylation (H3K79me2) at KMT2A target genes in addition to a downregulation of the KMT2A gene expression signature, providing evidence that it targets the KMT2A transcriptional complex and alters the epigenome. A cohort of relapsed/refractory KMT2Ar patients treated with this approach on a compassionate basis had an overall response rate of 90%. In conclusion, we report on a high throughput drug screen in primary pediatric leukemia specimens whose results translate into clinically meaningful responses. This innovative treatment approach is now being evaluated in a multi-institutional upfront trial for infants with newly diagnosed ALL.

Functional investigation of inherited noncoding genetic variation impacting the pharmacogenomics of childhood acute lymphoblastic leukemia treatment

Although acute lymphoblastic leukemia (ALL) is the most common childhood cancer, there is limited understanding of the contribution of inherited genetic variation on inter-individual differences in chemotherapy response. Defining genetic factors impacting therapy failure can help better predict response and identify drug resistance mechanisms. We therefore mapped inherited noncoding variants associated with chemotherapeutic drug resistance and/or treatment outcome to ALL cis-regulatory elements and investigated their gene regulatory potential and genomic connectivity using massively parallel reporter assays and promoter capture Hi-C, respectively. We identified 53 variants with reproducible allele-specific effects on transcription and high-confidence gene targets. Subsequent functional interrogation of the top variant (rs1247117) determined that it disrupted a PU.1 consensus motif and PU.1 binding affinity. Importantly, deletion of the genomic interval containing rs1247117 sensitized ALL cells to vincristine. Together, these data demonstrate that noncoding regulatory variation associated with diverse pharmacological traits harbor significant effects on allele-specific transcriptional activity and impact sensitivity to chemotherapeutic agents in ALL.

Characterisation of children and adolescents with acute lymphoblastic leukaemia who presented without peripheral blood blasts at diagnosis

Of 1003 children with acute lymphoblastic leukaemia (ALL), 147 (14.7%) presented without peripheral blood blasts (PBB). While absence of PBB was not independently associated with survival outcomes when compared to those with PBB, patients without PBB had distinct genetic and clinical characteristics. Notably, we identified a novel genotype-phenotype relationship, in that the patients without PBB had a significantly higher incidence of hyperdiploid B-ALL, accounting for almost half of all patients without PBB (46.9% vs. 22.7%, p < 0.001). Further, absence of PBB was associated with decreased rates of leukaemia involvement of the central nervous system (p < 0.001).

Association between body mass index at diagnosis and outcomes in Chinese children with newly diagnosed acute lymphoblastic leukemia

PURPOSE

Studies of the association between body mass index (BMI) at diagnosis and treatment outcome in children with acute lymphoblastic leukemia (ALL) have yielded inconsistent results. Hence, we conducted a retrospective study in a large cohort of Chinese children with ALL treated with contemporary protocols.

PATIENTS AND METHODS

A total of 1437 children (62.1% male; median age at diagnosis 5.7 years, range: 2.3-16.3 years) were enrolled in two consecutive clinical trials at the Shanghai Children's Medical Center. The rates of overall survival, event-free survival, relapse, treatment-related mortality, and adverse events were compared among patients who were underweight (BMI < 5th percentile), at a healthy weight (5th to 85th percentile), overweight (>85th to <95th percentile), and obese (≥95th percentile).

RESULTS

At diagnosis, 91 (6.3%) patients were underweight, 1070 (74.5%) were at a healthy weight, 91 (6.3%) were overweight, and 185 (12.9%) were obese. No significant association was found between weight status and 5-year overall survival, event-free survival, or relapse in the overall cohort. When analyzed as a continuous variable, a higher BMI Z-score was associated with treatment-related mortality (hazard ratio 1.33 (95% confidence interval [CI], 1.05-1.68%), p = 0.02). The treatment-related mortality rate was higher in the overweight (5.5%, 95% CI 0.8-10.2%) and obese (3.2%, 95% CI 0.6-5.8%) groups compared with the underweight (0.0%) and healthy-weight groups (1.9%, 95% CI 1.1-2.7%; p = 0.04). Multivariable analysis showed that children who were overweight had a higher risk of treatment-related mortality (hazard ratio 3.8, 95% CI 1.3-11.4).

CONCLUSION

While body weight status was not associated with event-free survival or overall survival, overweight patients were at higher risk of treatment-related mortality.

Vaccines against SARS-CoV-2 are safe to administer in patients with antibodies to pegaspargase

OBJECTIVE

Allergic reactions to pegaspargase during ALL therapy are typically due to antibodies against polyethylene glycol (PEG), which is also used as a stabilizing agent in mRNA-based SARS-CoV-2 vaccines. To evaluate the safety of these vaccines in patients with anti-pegaspargase antibodies.

METHODS

We retrospectively reviewed the records of patients treated for ALL who had received SARS-CoV-2 vaccinations. All patients had antibodies against pegaspargase assayed during ALL therapy prospectively and in response to clinical allergies. Symptoms of intolerance to vaccination were gathered retrospectively from chart abstraction.

RESULTS

SARS-CoV-2 vaccination was well tolerated in all 78 patients with prior exposure to pegaspargase as part of their leukemia therapy. No reactions were observed in the 54 patients without a history of anti-pegaspargase antibodies or in 19 patients with antibodies who received mRNA vaccination. 1 patient who received the polysorbate containing Janssen vaccine experienced mild symptoms after vaccination not meeting the criteria of clinical allergy which spontaneously resolved within 25 minutes.

CONCLUSION

SARS-CoV-2 vaccination is safe in this population.

Pharmacotypes across the genomic landscape of pediatric acute lymphoblastic leukemia and impact on treatment response

Contemporary chemotherapy for childhood acute lymphoblastic leukemia (ALL) is risk-adapted based on clinical features, leukemia genomics and minimal residual disease (MRD); however, the pharmacological basis of these prognostic variables remains unclear. Analyzing samples from 805 children with newly diagnosed ALL from three consecutive clinical trials, we determined the ex vivo sensitivity of primary leukemia cells to 18 therapeutic agents across 23 molecular subtypes defined by leukemia genomics. There was wide variability in drug response, with favorable ALL subtypes exhibiting the greatest sensitivity to L-asparaginase and glucocorticoids. Leukemia sensitivity to these two agents was highly associated with MRD although with distinct patterns and only in B cell ALL. We identified six patient clusters based on ALL pharmacotypes, which were associated with event-free survival, even after adjusting for MRD. Pharmacotyping identified a T cell ALL subset with a poor prognosis that was sensitive to targeted agents, pointing to alternative therapeutic strategies. Our study comprehensively described the pharmacological heterogeneity of ALL, highlighting opportunities for further individualizing therapy for this most common childhood cancer.

PAX5 epigenetically orchestrates CD58 transcription and modulates blinatumomab response in acute lymphoblastic leukemia

Blinatumomab is an efficacious immunotherapeutic agent in B cell acute lymphoblastic leukemia (B-ALL). However, the pharmacogenomic basis of leukemia response to blinatumomab is unclear. Using genome-wide CRISPR, we comprehensively identified leukemia intrinsic factors of blinatumomab sensitivity, i.e., the loss of CD58 as a top driver for resistance, in addition to CD19. Screening 1639 transcription factor genes, we then identified PAX5 as the key activator of CD58. ALL with the PAX5 P80R mutation also expressed the lowest level of CD58 among 20 ALL molecular subtypes in 1988 patients. Genome editing confirmed the effects of this mutation on CD58 expression and blinatumomab sensitivity in B-ALL, with validation in patient leukemic blasts. We described a PAX5-driven enhancer at the CD58 locus, which was disrupted by PAX5 P80R, and the loss of CD58 abolished blinatumomab-induced T cell activation with global changes in transcriptomic/epigenomic program. In conclusion, we identified previously unidentified genetic mechanisms of blinatumomab resistance in B-ALL, suggesting strategies for genomics-guided treatment individualization.

Evaluating blinatumomab implementation in low- and middle-income countries: a study protocol

Background

The recent implementation of novel therapies has accelerated progress in pediatric cancer care. Despite the significantly poorer survival of patients in low- and middle-income countries (LMICs), administation complexities and other significant resource barriers have limited the translation of these novel therapies in these regions. This study aims to develop a model that can be used to support the implementation of novel therapies, such as blinatumomab (bispecific antibody therapy for B-cell acute lymphoblastic leukemia [B-ALL]) in LMIC centers, with the long-term goal of developing an implementation framework for similar future efforts.

Methods

In this study, mixed methods will be applied to understand the key contextual considerations that can be accounted for through a training program and prospectively designed implementation activities. The Consolidated Framework for Implementation Research will guide the activities related to implementation evaluation in parallel with a drug donation program. A multidisciplinary research team comprising high- and low-middle income healthcare professionals, industry, and implementation scientists has been assembled with the common goal of improving safe access to blinatumomab. To assess the factors affecting blinatumomab administration, semi-structured interviews with diverse collaborators and quantitative assessments of organizational characteristics will be conducted, together with quantitative and qualitative assessments of feasibility, acceptability, appropriateness, and cost of blinatumomab implementation. A quantitative assessment of stakeholder perceptions of different implementation strategies used as part of the multifaceted approach will also be performed. Finally, we will examine the key domains and processes used and construct the implementation roadmap for translation of novel therapies.

Discussion

This study will rigorously develop an implementation roadmap for translation of novel therapies in low-resource settings. The knowledge gained in the formative assessment will reveal the priority areas and key implementation strategies. Thereby, the resultant roadmap will facilitate future scale-out strategies for novel therapies in LMICs, thus increasing access, building capacity for management, and ultimately improving the care for children in LMICs.

Preclinical and Pilot Study of Type I FLT3 Tyrosine Kinase Inhibitor, Crenolanib, with Sorafenib in Acute Myeloid Leukemia and FLT3-Internal Tandem Duplication

PURPOSE

To evaluate the safety, activity, and emergence of FLT3-kinase domain (KD) mutations with combination therapy of crenolanib and sorafenib in acute myeloid leukemia (AML) with FLT3-internal tandem duplication (ITD).

PATIENTS AND METHODS

After in vitro and xenograft efficacy studies using AML cell lines that have FLT3-ITD with or without FLT3-KD mutation, a pilot study was performed with crenolanib (67 mg/m2/dose, three times per day on days 1-28) and two dose levels of sorafenib (150 and 200 mg/m2/day on days 8-28) in 9 pediatric patients with refractory/relapsed FLT3-ITD-positive AML. Pharmacokinetic, pharmacodynamic, and FLT3-KD mutation analysis were done in both preclinical and clinical studies.

RESULTS

The combination of crenolanib and sorafenib in preclinical models showed synergy without affecting pharmacokinetics of each agent, inhibited p-STAT5 and p-ERK for up to 8 hours, and led to significantly better leukemia response (P < 0.005) and survival (P < 0.05) compared with single agents. Fewer FLT3-KD mutations emerged with dose-intensive crenolanib (twice daily) and low-intensity sorafenib (three times/week) compared with daily crenolanib or sorafenib (P < 0.05). The crenolanib and sorafenib combination was tolerable without dose-limiting toxicities, and three complete remissions (one with incomplete count recovery) and one partial remission were observed in 8 evaluable patients. Median crenolanib apparent clearance showed a nonsignificant decrease during treatment (45.0, 40.5, and 20.3 L/hour/m2 on days 1, 7, and 14, respectively) without drug-drug interaction. Only 1 patient developed a FLT3-KD mutation (FLT3 F691L).

CONCLUSIONS

The combination of crenolanib and sorafenib was tolerable with antileukemic activities and rare emergence of FLT3-TKD mutations, which warrants further investigation.

Bone mineral density (BMD) deficits in adult survivors of childhood cancer: Attributable risks and long-term consequences

e22021

Background: Survivors of childhood cancer are at risk for BMD deficits. Contributions of treatment, physical and lifestyle factors to overall risk are unknown as are long-term consequences of moderate and severe deficits. Methods: BMD deficits were evaluated in 3919 five-year childhood cancer survivors in the St. Jude Lifetime Cohort (median age 31.7 [range 18.0-69.9] years, 52.6% male, 80.4% non-Hispanic White) using lumbar quantitative computed tomography and classified by age- and sex-specific Z-scores as moderate (<-1SD) or severe deficit (<-2SD). Multivariable logistic regression estimated odds ratios (OR), risk factor attributable fractions (AF), and associations between BMD deficits and long-term outcomes (social/functional outcomes, fracture, mortality). Results: BMD deficits were moderate in 21.7% (95% CI 20.4%-23.0%) and severe in 6.9% (95% CI 6.1%-7.7%) of survivors. Risk factors for moderate deficit included age 5-9 years at diagnosis (OR 1.63, 95% CI 1.31-2.03), >20Gy cranial radiotherapy (OR 1.75, 95% CI 1.41-2.18), >3240 mg/m2 glucocorticoids (OR 1.34, 95% CI 1.09-1.66), and smoking (OR 1.55, 95% CI 1.27-1.90). AF were 7.2%, 0.7%, 5.9%, and 6.1% respectively; 80.1% of risk was unexplained. Risk factors for severe deficits included age 5-9 years at diagnosis (OR 1.95, 95% CI 1.36-2.80), BMI<18.5 kg/m2 (OR 3.95, 95% CI 2.28-6.85), >20Gy cranial radiotherapy (OR 5.22, 95% CI 3.74-7.30), testicular/pelvic radiation (OR 1.70, 95% CI 1.19-2.44), smoking (OR 1.71, 95% CI 1.21-2.43), and physical inactivity (OR 1.91, 95% CI 1.10-3.33). AFs were 10.9%, 7.0%, 2.9%, 11.5%, 6.7%, and 3.2% respectively; 57.8% of risk was unexplained. Those with deficits were less likely to live independently, to be employed, and more likely to require assistance with personal care needs (Table). Fracture risk was greatest among those with any BMD deficit, and mortality risk was greatest among those with severe deficits. Conclusions: Deficits in BMD among childhood cancer survivors are related not only to treatment, but also to modifiable health behaviors. In this population, children exposed to radiation or glucocorticoids are at greatest risk for poor bone quality and should be counselled to optimize health behaviors.[Table: see text]

Changes in body mass index, weight, and height in children with acute myeloid leukemia and the associations with outcome

Little is known about body composition changes in patients with acute myeloid leukemia (AML) during and after treatment or their associations with outcomes. Z-scores for body mass index (BMI), weight, and height at diagnosis, their longitudinal changes from diagnosis to 5 years off therapy, and their associations with adverse effects and outcomes were evaluated in 227 pediatric patients with AML enrolled in the AML02 and AML08 trials at St. Jude Children's Research Hospital between 2002-2017. The median Z-scores for baseline weight, height, and BMI were 0.193, 0.209, and 0.170, respectively, and those for weight and height decreased significantly during therapy to -0.038 and -0.163, respectively, at off-therapy (P < .001 for both). At 5 years off therapy, the Z-scores for weight and BMI had increased significantly to 0.492 (P = .003) and 0.911 (P < .001), respectively, whereas the height Z-score remained significantly lower at -0.066 (P < .001) compared with baseline. The height Z-score of transplant recipients decreased further from -0.211 at transplant to -0.617 12 months later (P < .001). Baseline BMI category and Z-score were not associated with outcomes, but higher weight Z-scores were associated with lower incidences of refractory or relapsed disease (hazard ratio [HR], 0.82; 95% confidence interval [CI], 0.67-0.99) and higher incidences of death in remission (HR, 1.31; 95% CI, 1.01-1.70). Furthermore, weight Z-score decrease during induction therapy was associated with gastrointestinal, hepatic, and infection toxicities during subsequent therapy and with death in remission (HR, 2.66; 95% CI, 1.11-6.45). Multidisciplinary monitoring for weight changes and short stature is required from diagnosis to the off-therapy period.

Integrated Genomic Analysis Identifies UBTF Tandem Duplications as a Recurrent Lesion in Pediatric Acute Myeloid Leukemia

The genetics of relapsed pediatric acute myeloid leukemia (AML) has yet to be comprehensively defined. Here, we present the spectrum of genomic alterations in 136 relapsed pediatric AMLs. We identified recurrent exon 13 tandem duplications (TD) in upstream binding transcription factor (UBTF) in 9% of relapsed AML cases. UBTF-TD AMLs commonly have normal karyotype or trisomy 8 with cooccurring WT1 mutations or FLT3-ITD but not other known oncogenic fusions. These UBTF-TD events are stable during disease progression and are present in the founding clone. In addition, we observed that UBTF-TD AMLs account for approximately 4% of all de novo pediatric AMLs, are less common in adults, and are associated with poor outcomes and MRD positivity. Expression of UBTF-TD in primary hematopoietic cells is sufficient to enhance serial clonogenic activity and to drive a similar transcriptional program to UBTF-TD AMLs. Collectively, these clinical, genomic, and functional data establish UBTF-TD as a new recurrent mutation in AML.

SIGNIFICANCE

We defined the spectrum of mutations in relapsed pediatric AML and identified UBTF-TDs as a new recurrent genetic alteration. These duplications are more common in children and define a group of AMLs with intermediate-risk cytogenetic abnormalities, FLT3-ITD and WT1 alterations, and are associated with poor outcomes. See related commentary by Hasserjian and Nardi, p. 173. This article is highlighted in the In This Issue feature, p. 171.

Simultaneous monitoring of disease and microbe dynamics through plasma DNA sequencing in pediatric patients with acute lymphoblastic leukemia

Treatment of acute lymphoblastic leukemia (ALL) necessitates continuous risk assessment of leukemic disease burden and infections that arise in the setting of immunosuppression. This study was performed to assess the feasibility of a hybrid capture next-generation sequencing panel to longitudinally measure molecular leukemic disease clearance and microbial species abundance in 20 pediatric patients with ALL throughout induction chemotherapy. This proof of concept helps establish a technical and conceptual framework that we anticipate will be expanded and applied to additional patients with leukemia, as well as extended to additional cancer types. Molecular monitoring can help accelerate the attainment of insights into the temporal biology of host-microbe-leukemia interactions, including how those changes correlate with and alter anticancer therapy efficacy. We also anticipate that fewer invasive bone marrow examinations will be required, as these methods improve with standardization and are validated for clinical use.

Impact of High Disease Burden on Survival in Pediatric Patients with B-ALL Treated with Tisagenlecleucel

CD19-specific chimeric antigen receptor (CAR) T-cell therapies, including the FDA-approved tisagenlecleucel, induce high rates of remission in pediatric patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, post-treatment relapse remains an issue. Optimal management of B-ALL after tisagenlecleucel treatment remains elusive, and continued tracking of outcomes is necessary to establish a standard of care for this population. We sought to evaluate outcomes on the real-world use of tisagenlecleucel in a contemporary pediatric patient population and to identify risk factors influencing event-free survival (EFS) and overall survival (OS). Additionally, we aimed to describe post-tisagenlecleucel management strategies, including use of allogeneic hematopoietic cell transplantation (AlloHCT) or repeat CAR T-cell infusions. We report on 31 pediatric and adolescent and young adult patients (AYA) with B-ALL, treated with lymphodepleting chemotherapy followed by tisagenlecleucel. Patients were treated at Johns Hopkins Hospital and St. Jude Children's Research Hospital between March 2018 and November 2020. Data on patient, disease, and treatment characteristics were collected retrospectively from medical records and described. EFS and OS were estimated by the Kaplan-Meier method and compared by the log-rank test. Single-factor and multiple-factor analysis of EFS and OS were performed by fitting Cox regression models. Of the 30 evaluable patients, 25 (83.3%) experienced a complete response, with 21 having negative minimal residual disease. Treatment was well tolerated, with expected rates of cytokine release syndrome (61.3%) and immune effector cell-associated neurotoxicity (29%). After initial complete response, 12 patients (48%) had subsequent disease recurrence, with CD19-negative relapse (n = 6) occurring sooner than CD19-positive relapse (P = .0125). With a median follow-up time of 386 days (range 11-1187 days), the EFS for the entire cohort (n = 31) at 6 and 12 months after infusion was 47% (95% confidence interval [CI], 28.4%-63.4%) and 35.2% (95% CI, 18.4%-52.5%), respectively. In multivariate analysis, high pretreatment leukemic burden (≥5% bone marrow blasts) was an independent risk factor for inferior EFS (HR 5.98 [95% CI, 1.1-32.4], P = .0380) and OS (HR 4.2 [95% CI, 1.33-13.39], P = .0148). Tisagenlecleucel induced high initial response rates in a contemporary cohort of pediatric and AYA patients with B-ALL. However, 48% of patients experienced subsequent disease relapse, including 6 with antigen-escape variants. This highlights a considerable limitation of single-agent autologous CD19-CAR T-cell therapy. Pretreatment leukemic disease burden of ≥5% blasts was significantly associated with worse outcomes in this study, including lower EFS and OS. Our findings suggest that reducing preinfusion leukemic burden is a viable treatment strategy to improve outcomes of CAR T-cell therapy.

Energy cost of walking in obese survivors of acute lymphoblastic leukemia: A report from the St. Jude Lifetime Cohort

Purpose

Adult survivors of childhood acute lymphoblastic leukemia (ALL) have impaired adaptive physical function and poor health-related quality of life (HRQoL). Obesity may contribute to these impairments by increasing the physiological cost of walking. Due to treatment exposures during ALL therapy, survivors' cost of walking may be more impacted by obesity than the general population. Therefore, we examined associations between obesity, persistent motor neuropathy, and energy cost of walking; and examined associations between energy cost of walking, adaptive physical function, and HRQoL, in adult survivors of childhood ALL vs. community controls.

Methods

Obesity was measured via body mass index (BMI) and body fat percentage. The physiological cost index (PCI) was calculated from the six-minute walk test. Adaptive physical functioning was measured using two tests: the timed up and go (TUG) test and the physical performance test. Persistent motor neuropathy was measured using the modified total neuropathy score; HRQoL was measured using the Short-Form-36 questionnaire. The associations between obesity and PCI were evaluated using multivariable linear regressions in adult survivors of childhood ALL (n = 1,166) and community controls (n = 491). Then, the associations between PCI, adaptive physical functioning and peripheral neuropathy were examined using multivariable linear regressions. Finally, to determine the association between obesity, and neuropathy on PCI, while accounting for potential lifestyle and treatment confounders, a three model, sequential linear regression was used.

Results

Obese individuals (BMI > 40 kg/m² and excess body fat percentage [males: >25%; females: >33%]) had higher PCI compared to those with normal BMI and body fat percentage (0.56 ± 0.01 vs. 0.49 ± 0.009 beats/meter p < .01; and 0.51 ± 0.007 vs. 0.48 ± .0006 beats/meter p < .01, respectively). Treatment exposures did not attenuate this association. Increased PCI was associated with longer TUG time in survivors, but not community controls (6.14 ± 0.02 s vs. 5.19 ± 0.03 s, p < .01). Survivors with PCI impairment >95th percentile of community controls had lower HRQoL compared to un-impaired ALL survivors: 46.9 ± 0.56 vs. 50.4 ± 1.08, respectively (p < .01).

Conclusion

Obesity was associated with increased PCI. Survivors with high PCI had disproportionately worse adaptive physical function and HRQoL compared to controls. Survivors with increased energy costs of walking may benefit from weight loss interventions.

Pediatric Cardio-Oncology Medicine: A New Approach in Cardiovascular Care

Survival for pediatric patients diagnosed with cancer has improved significantly. This achievement has been made possible due to new treatment modalities and the incorporation of a systematic multidisciplinary approach for supportive care. Understanding the distinctive cardiovascular characteristics of children undergoing cancer therapies has set the underpinnings to provide comprehensive care before, during, and after the management of cancer. Nonetheless, we acknowledge the challenge to understand the rapid expansion of oncology disciplines. The limited guidelines in pediatric cardio-oncology have motivated us to develop risk-stratification systems to institute surveillance and therapeutic support for this patient population. Here, we describe a collaborative approach to provide wide-ranging cardiovascular care to children and young adults with oncology diseases. Promoting collaboration in pediatric cardio-oncology medicine will ultimately provide excellent quality of care for future generations of patients.

Clinicopathologic and prognostic features of TdT-negative pediatric B-lymphoblastic leukemia

Little is known about B-lymphoblastic leukemia (B-ALL) that lacks expression of terminal deoxynucleotidyl transferase (TdT). To address this, we performed the largest study to date of TdT-negative B-ALL using data from St. Jude Total XV and XVI clinical trials. Compared to TdT-positive B-ALL (n = 896), TdT-negative B-ALL (n = 21) was associated with younger age (median, 1.4 versus 6.8 years, P < 0.001), higher white blood cell count (median, 52.8 versus 9.9 × 10⁹/L, P < 0.001), absence of hyperdiploidy (0 versus 27.8%, P = 0.002), KMT2A rearrangement (100 versus 1.9%, P < 0.001), and inferior 5-year event-free survival (EFS) (76.2 versus 90.3%, P = 0.047). In the context of KMT2A-rearranged B-ALL (n = 38), TdT-negativity was significantly associated with the MLLT1 rearrangement partner (P = 0.026) but was not independently predictive of survival, suggesting that the high-risk features of TdT-negative B-ALL are secondary to underlying KMT2A rearrangements. Finally, we compared the sensitivity of TdT-negativity to neuron-glial antigen 2 (NG.2) expression for the detection of KMT2A rearrangements and found that 63% of KMT2A-rearranged B-ALL cases not identified by NG.2 were TdT-negative. The results of this study expand the spectrum of immunophenotypic features that are specific for high-risk KMT2A rearrangements in pediatric B-ALL and can be readily implemented using existing standard acute leukemia flow cytometry panels.

Class II Human Leukocyte Antigen Variants Associate With Risk of Pegaspargase Hypersensitivity

We conducted the first human leukocyte antigen (HLA) allele and genome-wide association study to identify loci associated with hypersensitivity reactions exclusively to the PEGylated preparation of asparaginase (pegaspargase) in racially diverse cohorts of pediatric leukemia patients: St Jude Children's Research Hospital's Total XVI (TXVI, n = 598) and Children's Oncology Group AALL0232 (n = 2,472) and AALL0434 (n = 1,189). Germline DNA was genotyped using arrays. Genetic variants not genotyped directly were imputed. HLA alleles were imputed using SNP2HLA or inferred using BWAkit. Analyses between genetic variants and hypersensitivity were performed in each cohort first using cohort-specific covariates and then combined using meta-analyses. Nongenetic risk factors included fewer intrathecal injections (P = 2.7 × 10-5 in TXVI) and male sex (P = 0.025 in AALL0232). HLA alleles DQB1*02:02, DRB1*07:01, and DQA1*02:01 had the strongest associations with pegaspargase hypersensitivity (P < 5.0 × 10-5 ) in patients with primarily European ancestry (EA), with the three alleles associating in a single haplotype. The top allele HLA-DQB1*02:02 was tagged by HLA-DQB1 rs1694129 in EAs (r2  = 0.96) and less so in non-EAs. All single nucleotide polymorphisms associated with pegaspargase hypersensitivity reaching genome-wide significance in EAs were in class II HLA loci, and were partially replicated in non-EAs, as is true for other HLA associations. The rs9958628 variant, in ARHGAP28 (previously linked to immune response in children) had the strongest genetic association (P = 8.9 × 10-9 ) in non-EAs. The HLA-DQB1*02:02-DRB1*07:01-DQA1*02:01 associated with hypersensitivity reactions to pegaspargase is the same haplotype associated with reactions to non-PEGylated asparaginase, even though the antigens differ between the two preparations.