Urea Cycle Dysregulation Generates Clinically Relevant Genomic and Biochemical Signatures.

The urea cycle (UC) is the main pathway by which mammals dispose of waste nitrogen. We find that specific alterations in the expression of most UC enzymes occur in many tumors, leading to a general metabolic hallmark termed "UC dysregulation" (UCD). UCD elicits nitrogen diversion toward carbamoyl-phosphate synthetase2, aspartate transcarbamylase, and dihydrooratase (CAD) activation and enhances pyrimidine synthesis, resulting in detectable changes in nitrogen metabolites in both patient tumors and their bio-fluids. The accompanying excess of pyrimidine versus purine nucleotides results in a genomic signature consisting of transversion mutations at the DNA, RNA, and protein levels. This mutational bias is associated with increased numbers of hydrophobic tumor antigens and a better response to immune checkpoint inhibitors independent of mutational load. Taken together, our findings demonstrate that UCD is a common feature of tumors that profoundly affects carcinogenesis, mutagenesis, and immunotherapy response.

Comprehensive Analysis of Hypermutation in Human Cancer.

We present an extensive assessment of mutation burden through sequencing analysis of >81,000 tumors from pediatric and adult patients, including tumors with hypermutation caused by chemotherapy, carcinogens, or germline alterations. Hypermutation was detected in tumor types not previously associated with high mutation burden. Replication repair deficiency was a major contributing factor. We uncovered new driver mutations in the replication-repair-associated DNA polymerases and a distinct impact of microsatellite instability and replication repair deficiency on the scale of mutation load. Unbiased clustering, based on mutational context, revealed clinically relevant subgroups regardless of the tumors' tissue of origin, highlighting similarities in evolutionary dynamics leading to hypermutation. Mutagens, such as UV light, were implicated in unexpected cancers, including sarcomas and lung tumors. The order of mutational signatures identified previous treatment and germline replication repair deficiency, which improved management of patients and families. These data will inform tumor classification, genetic testing, and clinical trial design.

Suggested role for neutrophil extracellular trap formation in Ewing sarcoma immune microenvironment.

Ewing sarcoma (EWS) is a highly aggressive cancer with a survival rate of 70%-80% for patients with localized disease and under 30% for those with metastatic disease. Tumor-infiltrating neutrophils (TIN) can generate extracellular net-like DNA structures known as neutrophil extracellular traps (NETs). However, little is known about the presence and prognostic significance of tumor-infiltrating NETs in EWS. Herein, we investigated 46 patients diagnosed with EWS and treated in the Tel Aviv Medical Center between 2010 and 2021. TINs and NETs were identified in diagnostic biopsies of EWS by immunofluorescence. In addition, NETs were investigated in neutrophils isolated from peripheral blood samples of EWS patients at diagnosis and following neoadjuvant chemotherapy. The relationships between the presence of TINs and NETs, pathological and clinical features, and outcomes were analyzed. Our results demonstrate that TIN and NETs at diagnosis were higher in EWS patients with metastatic disease compared with those with local disease. High NET formation at diagnosis predicted poor response to neoadjuvant chemotherapy, relapse, and death from disease (p < 0.05). NET formation in peripheral blood samples at diagnosis was significantly elevated among patients with EWS compared with pediatric controls and decreased significantly following neoadjuvant chemotherapy. In conclusion, NET formation seems to have a role in the EWS immune microenvironment. Their presence can refine risk stratification, predict chemotherapy resistance and survival, and serve as a therapeutic target in patients with EWS.

Management of acute appendicitis in pediatric patients with acute leukemia: Insights from a single-center study.

Acute appendicitis (AA) in pediatric patients with acute leukemia mandates prompt treatment. Diagnosis presents challenges, relying on clinical and radiological assessments, often leading to treatment delays that may disrupt leukemia management. Our study on 14 such cases underscores the pivotal role of swift intervention. While conservative AA treatment may pose no risk to healthy children, our findings mandate the performance of laparoscopic appendectomy within 24 hours of diagnosis. This strategy yielded successful surgical outcomes while ensuring uninterrupted leukemia care. Our experience contributes important insights to the limited understanding of navigating this complex clinical scenario.

Ocular venous occlusion in pediatrics: Should thrombophilia investigation and anticoagulant treatment be initiated?

Retinal vein occlusion (RVO) and superior ophthalmic vein thrombosis (SOVT) are rare diseases in the pediatric population; however, the ophthalmic and neurologic morbidity are significant. As published data are scarce for these conditions, we present our experience with pediatric ocular venous thrombosis in four patients, and discuss recommended management for evaluation and treatment. We suggest performing thrombophilia workup for all pediatric patients with RVO or SOVT. In patients with thrombophilia risk factors or patients with additional thrombi, we highly recommend initiating anticoagulation therapy. There is a need for more research in order to determine the optimal management strategy.

Revaccination of children with acute lymphoblastic leukemia following completion of chemotherapy.

BACKGROUND: Intensive chemotherapy for acute lymphoblastic leukemia (ALL) may affect the immune system and potentially the immune memory causing antibodies provided by vaccination to disappear. There are disagreements regarding the guidelines for posttreatment immunization strategy. METHODS: Ninety-six children (aged 1-18 years at diagnosis) who completed chemotherapy for ALL were recruited. Antibody levels in the patient's serum against measles, varicella, polio, pertussis, hepatitis A, and hepatitis B were tested after completion of chemotherapy in patients who were fully vaccinated against these agents. Children who did not have positive serology to specific agents were revaccinated with a single dose accordingly. Antibody concentrations were measured again at least 4 weeks after revaccination. RESULTS: Positive antibody levels varied between the different agents. The highest percentage of positive serology was against polio (87%) and the lowest against pertussis (4%) (p < .001). There were significant differences between patients with high risk (HR) and non-HR ALL regarding serology status for some vaccines. After revaccination, the levels of response to each booster dose were significantly different: 100% after booster dose for varicella and polio, and only 34% after pertussis booster. CONCLUSIONS: Loss of humoral protection for vaccine preventable diseases is a common finding among patients with ALL. Revaccination with one dose of vaccine after completion of chemotherapy achieved seroconversion in 34-100% of the patients depending on the type of vaccine. We recommend this revaccination schedule to all children who completed ALL therapy and were previously fully vaccinated.

Prospective assessment of anxiety among pediatric oncology patients and their caregivers during the COVID-19 pandemic a cohort study.

To assess COVID-19-pandemic related anxiety and emotional-behavioral difficulties among oncologic children and their caregivers.Prospective cohort study conducted from March to November 2020.76 pediatric oncological and 28 nonmalignant hematological patients aged 1.6-23.4 years and their caregivers.A total of 104 families completed an age-specific self-report psychological assessment; of these, 20 oncologic families completed the assessment at two time points.Ten percent of the caregivers and 13.9% of the patients reported anxiety disorder. Additionally, 3.1% of the caregivers reported behavioral difficulties. No significant differences emerged between patients' self-reports and caregivers' reports. No differences emerged between oncological and nonmalignant hematological participants.The prevalence of anxiety associated with the COVID-19 pandemic was similar to the reported prevalence of anxiety following a diagnosis of pediatric malignancy.Real-time assessment of psychological effects revealed no COVID-19-associated anxiety. Nonetheless, late effects will need to be monitored.

[LANGERHANS CELL HISTIOCYTOSIS: A SINGLE CENTER EXPERIENCE IN THE PEDIATRIC HEMATO-ONCOLOGY DIVISION OF THE TEL-AVIV SOURASKY MEDICAL CENTER].

INTRODUCTION: Langerhans cell histiocytosis (LCH) is a histiocytic disorder which is characterized by a wide variety of clinical presentations and is prevalent mostly in children .This is a single center study reviewing experience in the treatment of LCH in a pediatric hemato-oncology ward over 25 years. We summarized the demographics, the locations of the disease, the treatments administered, the reactivations and the survival of the patients. METHODS: A retrospective analysis of files was performed from patients who were referred and treated at the Dana-Dwek Children's hospital in the Tel-Aviv Sourasky Medical Center between the years 1996-2020. RESULTS: One hundred and six patients with LCH were treated during the period 1996-2020 in the Pediatric Hemato-Oncology division. The diagnosis was confirmed by a biopsy from a lesion. The primary location of the disease was single system in 91% of patients (mostly bone lesions) and 9% multisystem disease. Forty-five patients (42.4%) were treated by upfront chemotherapy according to the Histiocyte Society guidelines. Twenty patients (19%) had reactivation of their disease. Ninety percent of the reactivations occurred in the first four years after diagnosis. There was no mortality in this cohort. CONCLUSIONS: This is a single center study summarizing the experience of a Pediatric Hemato-Oncology division in the Tel-Aviv Medical Center in the treatment of 106 patients with LCH over 25 years and is the first review of a large cohort of patients in Israel. The cohort was characterized by abundance of patients with bone disease and paucity of patients with multisystem disease with risk organ involvement. There was overall good response to treatment and all patients survived.

Syndromes predisposing to leukemia are a major cause of inherited cytopenias in children.

Prolonged cytopenias are a non-specific sign with a wide differential diagnosis. Among inherited disorders, cytopenias predisposing to leukemia require a timely and accurate diagnosis to ensure appropriate medical management, including adequate monitoring and stem cell transplantation prior to the development of leukemia. We aimed to define the types and prevalences of the genetic causes leading to persistent cytopenias in children. The study comprises children with persistent cytopenias, myelodysplastic syndrome, aplastic anemia, or suspected inherited bone marrow failure syndromes, who were referred for genetic evaluation from all pediatric hematology centers in Israel during 2016-2019. For variant detection, we used Sanger sequencing of commonly mutated genes and a custom-made targeted next-generation sequencing panel covering 226 genes known to be mutated in inherited cytopenias; the minority subsequently underwent whole exome sequencing. In total, 189 children with persistent cytopenias underwent a genetic evaluation. Pathogenic and likely pathogenic variants were identified in 59 patients (31.2%), including 47 with leukemia predisposing syndromes. Most of the latter (32, 68.1%) had inherited bone marrow failure syndromes, nine (19.1%) had inherited thrombocytopenia predisposing to leukemia, and three each (6.4%) had predisposition to myelodysplastic syndrome or congenital neutropenia. Twelve patients had cytopenias with no known leukemia predisposition, including nine children with inherited thrombocytopenia and three with congenital neutropenia. In summary, almost one third of 189 children referred with persistent cytopenias had an underlying inherited disorder; 79.7% of whom had a germline predisposition to leukemia. Precise diagnosis of children with cytopenias should direct follow-up and management programs and may positively impact disease outcome.

Tramadol Treatment for Chemotherapy-induced Mucositis Pain in Children.

Mucositis, a painful and debilitating condition, is a common side effect of chemotherapy. The role of tramadol in the treatment of mucositis in pediatric patients has not yet been determined. In this retrospective study, we evaluate whether tramadol as single agent achieved a reduction of pain intensity among oncologic children admitted for mucositis. In total, 34 of 54 (63%) episodes were treated with tramadol alone and achieved adequate pain relief. Tramadol's side effects were mild and manageable.

Prevalence and management of methotrexate-induced neurotoxicity in pediatric patients with osteosarcoma: a single-center experience.

AIMS: To determine the incidence, clinical presentation, and outcome of methotrexate (MTX) associated neurotoxicity in pediatric patients treated for osteosarcoma, with the aim of identifying possible risk factors and suggesting recommended treatment for these sequelae. MATERIALS AND METHODS: All medical files of patients treated for osteosarcoma in a single pediatric haemato-oncology center between November 2011 and August 2021 were retrospectively reviewed. All patients were treated according to the EURAMOS AOST0331 protocol, using cisplatin, doxorubicin, and high-dose MTX at a dose of 12 g/m2 over 4 h. RESULTS: Seventy-eight patients with osteosarcoma were identified (age range 5 to 23 years, 42 males). Seven patients (9%) sustained neurotoxicity following treatment with high-dose MTX. Manifestations of neurotoxicity included among others, generalized seizures, confusion, encephalopathy, dysarthria, and choreiform movements. All but one episode occurred following two sequential cycles of high-dose MTX. All 7 had subacute toxicity, 5-10 days following MTX administration, and 1 had both acute and subacute toxicity. Brain MRI was performed for all patients and demonstrated typical MRI changes attributed to MTX neurotoxicity in 4 of them. Two patients received aminophylline; one patient received dextromethorphan. Patients with normal MRI imaging resumed MTX therapy without any sequels. No risk factors were found for high-dose MTX-related toxicity occurrence. CONCLUSIONS: The time of risk of neurotoxicity due to high-dose MTX treatment for osteosarcoma is days 5-10 following two sequential treatment cycles. These findings together with treatment options for these adverse effects should be detailed in the therapeutic protocol of MTX use among pediatric patients with osteosarcoma.

Diverse presentation and tailored treatment of infantile myofibromatosis: A single-center experience.

BACKGROUND: Infantile myofibromatosis (IM) is a rare benign fibrous tumor with diverse clinical presentations and treatments, such as watchful waiting, surgical excision, and low-dose chemotherapy. PROCEDURE: Clinical presentation and tailored treatment of five infants with solitary and generalized IM are described, together with a review of the literature. RESULTS: Three patients underwent total-body magnetic resonance imaging (MRI) at diagnosis and during follow up, which revealed disease extension that aided in designing treatment. Visceral involvement included central nervous system, cardiac, gastrointestinal, muscle, bone, and subcutaneous tissue lesions. The patient with the solitary form of IM was followed up without treatment and had spontaneous improvement. Patients with the multicentric form received intravenous low-dose methotrexate and vinblastine chemotherapy. One patient who received oral methotrexate due to cardiac involvement and unfeasible central line access had excellent results. Recurrence was successfully treated by the same methotrexate and vinblastine regimen as that administered at diagnosis. CONCLUSIONS: We suggest screening all patients with one or more IM lesions by means of total body MRI due to its inherent superior soft tissue resolution. Total-body MRI may also be used for routine follow up. Oral methotrexate can be administered successfully in patients that lack central line access, and recurrent lesions can be treated with the same chemotherapeutic combination as that given at diagnosis. Long-term follow up is needed, since recurrence could appear years after initial presentation of the disease.

Hematopoietic stem cell transplantation for mitochondrial neurogastrointestinal encephalopathy: A single-center experience underscoring the multiple factors involved in the prognosis.

BACKGROUND: Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a progressive autosomal recessive disorder characterized by cachexia, gastrointestinal (GI) dysmotility, ptosis, peripheral neuropathy, and brain magnetic resonance imaging (MRI) white matter changes. Bi-allelic TYMP mutations lead to deficient thymidine phosphorylase (TP) activity, toxic accumulation of plasma nucleosides (thymidine and deoxyuridine), nucleotide pool imbalances, and mitochondrial DNA (mtDNA) instability. Death is mainly due to GI complications: intestinal perforation, peritonitis, and/or liver failure. Based on our previous observations in three patients with MNGIE that platelet infusions resulted in a transient 40% reduction of plasma nucleoside levels, in 2005 we performed the first hematopoietic stem cell transplantation (HSCT) worldwide as a life-long source of TP in a patient with MNGIE. PROCEDURE: HSCT was performed in a total of six patients with MNGIE. The multiple factors involved in the prognosis of this cohort were analyzed and compared to the literature experience. RESULTS: Cell source was bone marrow in five patients and peripheral stem cells in one, all from fully human leukocyte antigen (HLA)-matched related donors, including four who were TYMP mutation carriers. Four of six (66%) survived compared to the 37% survival rate in the literature. Reduced intensity conditioning regimen contributed to secondary graft failure in two patients. Fifteen years post HSCT, the first transplanted patient is seemingly cured. Severe GI symptoms before transplantation were mostly irreversible and were poor prognostic factors. CONCLUSIONS: Allogenic HSCT could constitute a curative therapeutic option for carefully selected, young, presymptomatic, or mildly affected patients. Timing, donor selection, and optimal conditioning protocol are major determinants of outcome. HSCT is inadvisable in patients with advanced MNGIE disease.

Mucormycosis in children with haematological malignancies is a salvageable disease: a report from the Israeli Study Group of Childhood Leukemia.

Mucormycosis has emerged as an increasingly important cause of morbidity and mortality in immunocompromised patients, but contemporary data in children are lacking. We conducted a nationwide multicentre study to investigate the characteristics of mucormycosis in children with haematological malignancies. The cohort included 39 children with mucormycosis: 25 of 1136 children (incidence 2·2%) with acute leukaemias prospectively enrolled in a centralized clinical registry in 2004-2017, and an additional 14 children with haematological malignancies identified by retrospective search of the databases of seven paediatric haematology centres. Ninety-two percent of mucormycosis cases occurred in patients with acute leukaemias. Mucormycosis was significantly associated with high-risk acute lymphoblastic leukaemia (OR 3·75; 95% CI 1·51-9·37; P = 0·004) and with increasing age (OR 3·58; 95% CI 1·24-9·77; P = 0·01). Fifteen patients (38%) died of mucormycosis. Rhinocerebral pattern was independently associated with improved 12-week survival (OR 9·43; 95% CI 1·47-60·66; P = 0·02) and relapsed underlying malignancy was associated with increased 12-week mortality (OR 6·42; 95% CI, 1·01-40·94; P = 0·05). In patients receiving frontline therapy for their malignancy (n = 24), one-year cumulative mucormycosis-related mortality was 21 ± 8% and five-year overall survival was 70 ± 8%. This largest paediatric population-based study of mucormycosis demonstrates that children receiving frontline therapy for their haematological malignancy are often salvageable.

Poorer outcome of childhood acute lymphoblastic leukemia in the Bedouin population: A report from the Berlin-Frankfurt-Muenster-based Israeli national protocols.

BACKGROUND: Therapy outcomes for childhood acute lymphoblastic leukemia (ALL) had substantially improved in the last decades, but variability across racial and ethnic groups was identified in some clinical studies. In this study, we aimed to investigate whether such a difference in outcome is found in the diverse ethnicities in Israel as well. METHODS: A retrospective study was conducted among 1154 patients (855 Jews, 195 Muslims, 52 Bedouins, 26 Druze, and 26 others) aged 1 to 21 years, who were diagnosed with ALL between 1989 and 2011 and were treated according to the same Berlin-Frankfurt-Muenster-based Israel National Study protocols. RESULTS: Bedouins had a higher incidence of t(1;19) (16% vs 3% for non-Bedouins) and a lower incidence of high-hyperdiploidy (10% vs 25% for non-Bedouins) (P = 0.01). Five-year event-free survival (EFS) and overall survival (OS) were poorer for the Bedouins (60.3% ± 7.2% and 63.1% ± 7.2%, respectively) compared with the Jews, Muslims, and Druze (80.4% ± 1.4%, 77.3% ± 3.2%, and 84% ± 7.3%, respectively, for EFS [P = 0.02], and 86.3% ± 1.2%, 82.3% ± 2.9%, and 88.3% ± 6.4%, respectively, for OS [P = 0.002]). Adherence to intensive chemotherapy was similar between the Muslims and the Bedouins. CONCLUSIONS: Our findings suggest that the Bedouins, a highly inbred ethnic Arab people, may be considered a higher risk group that may need more intensive chemotherapy and/or supportive care in order to improve their outcome.

Neutrophil Elastase Activity as a Surrogate Marker for Neutrophil Extracellular Trap Formation following Hematopoietic Stem Cell Transplantation.

Impaired neutrophil extracellular trap (NET) formation compromises the host defense after engraftment following hematopoietic stem cell transplantation (HSCT) despite adequate neutrophil counts. The aims of the present study were to determine reference ranges for the activity of key enzymes of NET formation-neutrophil elastase (NE) and myeloperoxidase (MPO)-in a healthy population and to unravel the recovery dynamics of NET formation over time following HSCT, along with NE and MPO enzymatic activities. Reference ranges of NE and MPO activity were derived from 50 healthy volunteers. During 2017 to 2018, 11 consecutive pediatric patients undergoing allogeneic or autologous HSCT were recruited at a single referral center for pediatric hemato-oncology. Patients were followed for up to 1 year following engraftment. The mean reference value was 7.5 ± .4 mU for NE activity and 2.17 ± .4 U for MPO activity in the healthy population, and enzymatic activity of MPO was significantly higher in males. At 3 weeks following neutrophil engraftment, all study participants demonstrated extremely low enzymatic NE activity, whereas MPO activity was above the lower normal reference range at all time points. Reduced NE activity corresponded to the inability to form NETs. Neutrophil function improved over time, but partial impairment persisted for 7 months following transplantation. The ability of neutrophils to form NETs was significantly impaired for 3 weeks after engraftment in the setting of HSCT, exposing patients to bacterial infections. NE activity might serve as a surrogate marker for the capacity of neutrophils to form NETs.

Thrombophilia screening and thromboprophylaxis may benefit specific ethnic subgroups with paediatric acute lymphoblastic leukaemia.

This study investigated the prevalence of inherited thrombophilia, risk of venous thromboembolism (VTE) and benefit of low molecular weight heparin prophylaxis in 476 Israeli children with acute lymphoblastic leukaemia (ALL) treated between 2004 and 2016. Thrombophilia was found in 15·5%. Arab children had a higher prevalence of F5 R506Q (factor V Leiden) than Jewish children (19·4% vs. 2·9%, P < 0·01). Patients with thrombophilia had higher VTE rates VTE (26·5% vs. 5·6%, P < 0·001). None of the thrombophilic children given prophylaxis had severe VTE. Routine evaluation for inherited thrombophilia followed by thromboprophylaxis when findings are positive may benefit at-risk patients with ALL.

Blinatumomab as a bridge to further therapy in cases of overwhelming toxicity in pediatric B-cell precursor acute lymphoblastic leukemia: Report from the Israeli Study Group of Childhood Leukemia.

Tremendous progress in the therapy of pediatric acute lymphoblastic leukemia (ALL) has been achieved through combination cytotoxic chemotherapy, leading to high cure rates, at the cost of significant life-threatening toxicity. The bispecific T-cell engager blinatumomab, recently approved for relapsed/refractory ALL, has a unique nonmyelotoxic toxicity profile. As blinatumomab causes B-cell depletion, the safety of its use during severe chemotherapy-induced toxicity is unclear. We report 11 pediatric patients with ALL, treated with blinatumomab following overwhelming chemotherapy-associated toxicity, with recovery of all patients and successful bridging to further antileukemia therapy. Blinatumomab can be considered for rare patients who cannot tolerate cytotoxic therapy.