Faculty Bibliography

Genetic alterations in the RUNX1 gene are associated with benign and malignant blood disorders, particularly of megakaryocyte and myeloid lineages. The role of RUNX1 in acute lymphoblastic leukemia (ALL) is less clear, particularly how germline genetic variation influences the predisposition to this type of leukemia. Sequencing 4,836 children with B-ALL and 1,354 cases of T-ALL, we identified 31 and 18 germline RUNX1 variants, respectively. RUNX1 variants in B-ALL consistently showed minimal damaging effects. By contrast, 6 T-ALL-related variants result in drastic loss of RUNX1 activity as a transcription activator in vitro. Ectopic expression of dominant-negative RUNX1 variants in human CD34+ cells repressed differentiation into erythroid, megakaryocytes, and T cells, while promoting myeloid cell development. Chromatin immunoprecipitation sequencing of T-ALL models showed distinctive patterns of RUNX1 binding by variant proteins. Further whole genome sequencing identified JAK3 mutation as the most frequent somatic genomic abnormality in T-ALL with germline RUNX1 variants. Co-introduction of RUNX1 variant and JAK3 mutation in hematopoietic stem and progenitor cells in mice gave rise to T-ALL with early T-cell precursor phenotype. Taken together, these results indicated that RUNX1 is an important predisposition gene for T-ALL and pointed to novel biology of RUNX1-mediated leukemogenesis in the lymphoid lineages.

Infants with KMT2A-rearranged acute lymphoblastic leukemia (KMT2A-r ALL) have a poor prognosis. KMT2A-r ALL overexpresses FLT3, and the FLT3 inhibitor (FLT3i) lestaurtinib potentiates chemotherapy-induced cytotoxicity in preclinical models. Children's Oncology Group (COG) AALL0631 tested whether adding lestaurtinib to post-induction chemotherapy improved event-free survival (EFS). After chemotherapy induction, KMT2A-r infants received either chemotherapy only or chemotherapy plus lestaurtinib. Correlative assays included FLT3i plasma pharmacodynamics (PD), which categorized patients as inhibited or uninhibited, and FLT3i ex vivo sensitivity (EVS), which categorized leukemic blasts as sensitive or resistant. There was no difference in 3-year EFS between patients treated with chemotherapy plus lestaurtinib (n = 67, 36 ± 6%) vs. chemotherapy only (n = 54, 39 ± 7%, p = 0.67). However, for the lestaurtinib-treated patients, FLT3i PD and FLT3i EVS significantly correlated with EFS. For FLT3i PD, EFS for inhibited/uninhibited was 59 ± 10%/28 ± 7% (p = 0.009) and for FLTi EVS, EFS for sensitive/resistant was 52 ± 8%/5 ± 5% (p < 0.001). Seventeen patients were both inhibited and sensitive, with an EFS of 88 ± 8%. Adding lestaurtinib did not improve EFS overall, but patients achieving potent FLT3 inhibition and those whose leukemia blasts were sensitive FLT3-inhibition ex vivo did benefit from the addition of lestaurtinib. Patient selection and PD-guided dose escalation may enhance the efficacy of FLT3 inhibition for KMT2A-r infant ALL.

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer and advances in its clinical and laboratory biology have grown exponentially over the last few decades. Treatment outcome has improved steadily with over 90% of patients surviving 5 years from initial diagnosis. This success can be attributed in part to the development of a risk stratification approach to identify those subsets of patients with an outstanding outcome that might qualify for a reduction in therapy associated with fewer short and long term side effects. Likewise, recognition of patients with an inferior prognosis allows for augmentation of therapy, which has been shown to improve outcome. Among the clinical and biological variables known to impact prognosis, the kinetics of the reduction in tumor burden during initial therapy has emerged as the most important prognostic variable. Specifically, various methods have been used to detect minimal residual disease (MRD) with flow cytometric and molecular detection of antigen receptor gene rearrangements being the most common. However, many questions remain as to the optimal timing of these assays, their sensitivity, integration with other variables and role in treatment allocation of various ALL subgroups. Importantly, the emergence of next generation sequencing assays is likely to broaden the use of these assays to track disease evolution. This review will discuss the biological basis for utilizing MRD in risk assessment, the technical approaches and limitations of MRD detection and its emerging applications.

PURPOSE/OBJECTIVE: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: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:< .0001). CONCLUSION/CONCLUSIONS: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.

Adolescents and young adults (AYAs) with acute lymphoblastic leukemia have improved outcomes when treated with pediatric-inspired regimens. CALGB 10403 was the largest prospective study to evaluate the feasibility of using a pediatric regimen in AYAs with acute lymphoblastic leukemia up to 40 years of age. This article presents the toxicity events observed in the CALGB 10403 study and compares these toxicities vs those observed among AYAs treated on the same arm of the companion Children's Oncology Group (COG) AALL0232 study. Toxicities in CALGB 10403 were similar to those observed in COG AALL0232. Some grade 3 to 4 adverse events were more often reported in CALGB 10403 compared with COG AALL0232 (hyperglycemia, hyperbilirubinemia, transaminase elevation, and febrile neutropenia). Adverse events correlated with body mass index ≥30 kg/m2 and some with increasing age. The mortality rate in CALGB 10403 was low (4%) and similar to that in the COG AALL0232 trial. A caveat to this analysis is that only 39% of CALGB 10403 patients completed all planned protocol treatment. In COG AALL0232, although 74% of patients aged <18 years completed treatment, only 57% of patients aged ≥18 years completed treatment. This scenario suggests that issues associated with age and treating physician may be a factor. Due to its improved survival rates compared with historical controls, the CALGB 10403 regimen is now a standard of care. The hope is that the rate of protocol completion will increase as more familiarity is gained with this regimen. These trials were registered at www.clinicaltrials.gov as #NCT00558519 (CALGB 10403) and #NCT00075725 (COG AALL0232).

PURPOSE/UNASSIGNED: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/UNASSIGNED:(MTX40). RESULTS/UNASSIGNED:= .92 and .89). CONCLUSIONS/UNASSIGNED:once weekly. 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.