Faculty Bibliography

PURPOSE/OBJECTIVE:Blinatumomab, a bispecific T-cell engager immunotherapy, is efficacious in relapsed/refractory B-cell ALL (B-ALL) and has a favorable toxicity profile. One aim of the Children's Oncology Group AALL1331 study was to compare survival of patients with low-risk (LR) first relapse of B-ALL treated with chemotherapy alone or chemotherapy plus blinatumomab. PATIENTS AND METHODS/METHODS:After block 1 reinduction, patients age 1-30 years with LR first relapse of B-ALL were randomly assigned to block 2/block 3/two continuation chemotherapy cycles/maintenance (arm C) or block 2/two cycles of continuation chemotherapy intercalated with three blinatumomab blocks/maintenance (arm D). Patients with CNS leukemia received 18 Gy cranial radiation during maintenance and intensified intrathecal chemotherapy. The primary and secondary end points were disease-free survival (DFS) and overall survival (OS). RESULTS:= .53). Blinatumomab was well tolerated and patients had low adverse event rates. CONCLUSION/CONCLUSIONS:For children, adolescents, and young adults with B-ALL in LR first relapse, there was no statistically significant difference in DFS or OS between the blinatumomab and standard chemotherapy arms overall. However, blinatumomab significantly improved DFS and OS for the two thirds of patients with BM ± EM relapse, establishing a new standard of care for this population. By contrast, similar outcomes and poor DFS for both arms were observed in the one third of patients with IEM; new treatment approaches are needed for these patients (ClinicalTrials.gov identifier: NCT02101853).

RAS mutations are frequently observed in childhood B-cell acute lymphoblastic leukemia (B-ALL) and previous studies have yielded conflicting results as to whether they are associated with a poor outcome. We and others have demonstrated that the mitogen-activated protein kinase-extracellular signal-regulated kinase (MAPK) pathway can be activated through epigenetic mechanisms in the absence of RAS pathway mutations. Herein, we examined whether MAPK activation, as determined by measuring phosphorylated extracellular signal-regulated kinase (pERK) levels in 80 diagnostic patient samples using phosphoflow cytometry, could be used as a prognostic biomarker for pediatric B-ALL. The mean fluorescence intensity of pERK (MFI) was measured at baseline and after exogenous stimulation with or without pretreatment with the mitogen-activated protein kinase kinase (MEK) inhibitor trametinib. Activation levels (MFI stimulated/MFI baseline) ranged from 0.76 to 4.40 (median = 1.26), and inhibition indexes (MFI stimulated/MFI trametinib stimulated) ranged from 0.439 to 5.640 (median = 1.30), with no significant difference between patients with wildtype versus mutant RAS for either. Logistic regression demonstrated that neither MAPK activation levels nor RAS mutation status at diagnosis alone or in combination was prognostic of outcome. However, 35% of RAS wildtype samples showed MAPK inhibition indexes greater than the median, thus raising the possibility that therapeutic strategies to inhibit MAPK activation may not be restricted to patients whose blasts display Ras pathway defects.

Background and Aims: Standard treatment for B-ALL first relapse begins with reinduction chemotherapy. Predictors of severe toxicity and poor efficacy would identify patients for whom alternative approaches could be prioritized.
Method(s): Patients aged 1-30 years received reinduction with vincristine, dexamethasone, pegaspargase, mitoxantrone and intrathecal chemotherapy (UKALLR3 mitoxantrone arm), followed by risk stratification and randomization to chemotherapy vs. blinatumomab. We reviewed reinduction response [morphologic and flow minimal residual disease (MRD)] and adverse events (AEs) by age (<12 vs 12-17 vs 18+ years), sex, site of relapse [marrow vs extramedullary (EM)] and duration of first remission (<18 months vs. 18-36 months vs >36 months). Pearson's chi-squared test or Fisher's exact test was used to evaluate associations. P values are two-sided and a p value <0.05 was considered statistically significant.
Result(s): Of 662 patients starting reinduction, 24 (4%) died during reinduction (22 AEs; 2 disease progression). Death was associated only with shorter first remission duration (p=0.006). Of those surviving, 44 (7%) had treatment failure (M3 marrow and/or persistent CNS disease) and 67 (11%) had non-fatal severe AEs (grade 4 febrile neutropenia, infection, sepsis or mucositis). Treatment failure was associated with site of relapse (marrow greater than EM, p=0.029) and shorter first remission duration (p<0.001). Severe AEs were associated only with older age (p=0.014). Of patients without death or treatment failure, 272 (46%) were MRD-positive (>=0.01%); MRD-positivity was associated with older age (p=0.038) and marrow relapse (p<0.001).
Conclusion(s): Patients with early relapse are at higher risk of toxic death and early treatment failure. Older patients are at higher risk of non-fatal severe AEs and MRD positivity. Patients with bone marrow relapse are at higher risk of early treatment failure and MRD positivity. Males and females have similar risks of poor reinduction outcomes

PURPOSE/OBJECTIVE:Pediatric oncology patients undergoing active chemotherapy are suspected to be at a high risk for severe disease secondary to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection; however, data to support this are lacking. We aim to describe the characteristics of coronavirus disease 2019 (COVID-19) in this population and also its impact on pediatric cancer care in the New York region during the peak of the pandemic. PATIENTS AND METHODS/METHODS:This multicenter, retrospective study included 13 institutions. Clinical and laboratory information on 98 patients ≤21 years of age receiving active anticancer therapy, who tested positive for SARS-CoV-2 by nasopharyngeal swab polymerase chain reaction (PCR), was collected. RESULTS:Of the 578 pediatric oncology patients tested for COVID-19, 98 were positive, of whom 73 were symptomatic. Most experienced mild disease, 28 required inpatient management, 25 needed oxygen support, and seven required mechanical ventilation. There is a slightly higher risk of severe disease in males and obese patients, though not statistically significant. Persistent lymphopenia was noted in severe cases. Delays in cancer therapy occurred in 67% of SARS-CoV-2-positive patients. Of four deaths, none were solely attributable to COVID-19. The impact of the pandemic on pediatric oncology care was significant, with 54% of institutions reporting delays in chemotherapy, 46% delays in surgery, and 30% delays in transplant. CONCLUSION/CONCLUSIONS:In this large multi-institutional cohort, we observed that mortality and morbidity from COVID-19 amongst pediatric oncology patients were low overall, but higher than reported in general pediatrics. Certain subgroups might be at higher risk of severe disease. Delays in cancer care due to SARS-CoV-2 remain a concern.

Although B cell acute lymphoblastic leukemia (ALL) is the most common malignancy in children and while highly curable, it remains a leading cause of cancer-related mortality. The outgrowth of tumor subclones carrying mutations in genes responsible for resistance to therapy has led to a Darwinian model of clonal selection. Previous work has indicated that alterations in the epigenome might contribute to clonal selection yet the extent to which the chromatin state is altered under the selective pressures of therapy is unknown. To address this, we performed chromatin immunoprecipitation, gene expression analysis, and enhanced reduced representation bisulfite sequencing on a cohort of paired diagnosis and relapse samples from individual patients who all but one relapsed within 36 months of initial diagnosis. The chromatin state at diagnosis varied widely among patients: while the majority of peaks remained stable between diagnosis and relapse, yet a significant fraction were either lost or newly gained with some patients showing few differences and others showing massive changes of the epigenetic state. Evolution of the epigenome was associated with pathways previously linked to therapy resistance as well as novel candidate pathways through alterations in pyrimidine biosynthesis and downregulation of polycomb repressive complex 2 targets. Three novel, relapse-specific super-enhancers were shared by a majority of patients including one associated with S100A8, the top upregulated gene seen at relapse in childhood B-ALL. Overall, our results support a role of the epigenome in clonal evolution and uncover new candidate pathways associated with relapse.

Reverse phase protein arrays (RPPA) can assess protein expression and activation states in large numbers of samples (n > 1000) and evidence suggests feasibility in the setting of multi-institution clinical trials. Despite evidence in solid tumors, little is known about protein stability in leukemia. Proteins collected from leukemia cells in blood and bone marrow biopsies must be sufficiently stable for analysis. Using 58 leukemia samples, we initially assessed protein/phospho-protein integrity for the following preanalytical variables: 1) shipping vs local processing, 2) temperature (4 °C vs ambient temperature), 3) collection tube type (heparin vs Cell Save (CS) preservation tubes), 4) treatment effect (pre- vs post-chemotherapy) and 5) transit time. Next, we assessed 1515 samples from the Children's Oncology Group Phase 3 AML clinical trial (AAML1031, NCT01371981) for the effects of transit time and tube type. Protein expression from shipped blood samples was stable if processed in ≤72 h. While protein expression in pre-chemotherapy samples was stable in both heparin and CS tubes, post-chemotherapy samples were stable in only CS tubes. RPPA protein extremes is a successful quality control measure to identify and exclude poor quality samples. These data demonstrate that a majority of shipped proteins can be accurately assessed using RPPA. SIGNIFICANCE: RPPA can assess protein abundance and activation states in large numbers of samples using small amounts of material, making this method ideal for use in multi-institution clinical trials. However, there is little known about the effect of preanalytical handling variables on protein stability and the integrity of protein concentrations after sample collection and shipping. In this study, we used RPPA to assess preanalytical variables that could potentially affect protein concentrations. We found that the preanalytical variables of shipping, transit time, and temperature had minimal effects on RPPA protein concentration distributions in peripheral blood and bone marrow, demonstrating that these preanalytical variables could be successfully managed in a multi-site clinical trial setting.

Survival of children with relapsed acute lymphoblastic leukemia is poor and understanding mechanisms underlying resistance is essential in developing new therapy. Relapse-specific heterozygous deletions in MSH6, a crucial part of DNA Mismatch Repair, are frequently detected. Our aim was to determine whether MSH6 deletion results in a hypermutator phenotype associated with generation of secondary mutations involved in drug resistance or leads to a failure to initiate apoptosis directly in response to chemotherapeutic agents. We knocked down MSH6 in mismatch repair proficient cell lines (697 and UOCB1) and showed significant increases in IC50s to 6-Thioguanine & 6-Mercaptopurine (697: 26- and 9-fold; UOCB1: 5- and 8-fold) in vitro, as well as increased resistance to 6-Mercaptopurine treatment in vivo. No shift in IC50 was observed in deficient cells (Reh & RS4;11). 697 MSH6 knockdown resulted in increased DNA thioguanine nucleotide levels compared to non-targeted cells (3,070 versus 1,722 fmol/mg DNA) with no difference observed in mismatch repair deficient cells. Loss of MSH6 did not give rise to microsatellite instability in cells lines or clinical samples nor did it significantly increase mutation rate, but rather resulted in a defect in cell cycle arrest upon thiopurine exposure. MSH6 knockdown cells showed minimal activation of checkpoint regulator CHK1, ɣH2AX (DNA damage marker) and p53 levels upon treatment with thiopurines, consistent with intrinsic chemoresistance due to failure to recognize thioguanine nucleotide mismatching and initiate mismatch repair. Aberrant MSH6 adds to the list of alterations/mutations associated with acquired resistance to purine analogues emphasizing the importance of thiopurine therapy.

Ewing sarcoma (EWS) is a primitive neuroectodermal tumor arising in bone or soft tissue. It is the second most common primary bone malignancy of children and adolescents, with a peak incidence in the second decade of life. It most often arises in the long bones of the extremities and pelvis. Here, we present a novel case of EWS arising from the mastoid bone in a 5-year-old African American male who presented with symptoms of acute mastoiditis. This unique presentation highlights the importance of considering EWS in a patient who presents with atypical mastoiditis or a rapidly growing mass in the postauricular region.

INTRODUCTION: The improvement in outcomes for children with acute lymphoblastic leukemia (ALL) is one of the greatest success stories of modern oncology however the prognosis for patients who relapse remains dismal. Recent discoveries by high resolution genomic technologies have characterized the biology of relapsed leukemia, most notably pathways leading to the drug resistant phenotype. These observations open the possibility of targeting such pathways to prevent and/or treat relapse. Likewise, early experiences with new immunotherapeutic approaches have shown great promise. Areas Covered: We performed a literature search on PubMed and recent meeting abstracts using the keywords below. We focus on the biology and clonal evolution of relapsed disease and highlight potential new targets of therapy. We further summarize the results of early trials of the three most prominent immunotherapy agents currently under investigation. Expert Commentary: Discovery of targetable pathways that lead to drug resistance and recent breakthroughs in immunotherapy show great promise towards treating this aggressive disease. The best way to treat relapse, however, is to prevent it which makes incorporation of these new approaches into frontline therapy the best approach. Challenges remain to balance efficacy with toxicity and to prevent the emergence of resistant subclones which is why combining these newer agents with conventional chemotherapy will likely become standard of care.