Abstract Background Prompt diagnosis of childhood acute lymphoblastic leukemia (ALL) remains a clinical challenge, particularly in children presenting with normal blood counts and musculoskeletal symptoms. With the increasing use of magnetic resonance imaging (MRI) in evaluating such complaints, bone marrow signal alterations may be detected before hematologic abnormalities appear. Previous studies have described characteristic MRI patterns in leukemia, suggesting potential for earlier recognition. This study aims to clarify the role of MRI in the diagnostic pathway of pediatric ALL and to define radiological findings that should prompt bone marrow examination. We retrospectively reviewed all patients diagnosed with ALL at our institution between 2006 and 2024 and included those who underwent MRI prior to diagnosis. Clinical data were collected, and all MRI studies were re-evaluated by an experienced pediatric radiologist. Results Twenty pediatric patients with ALL were included. Due to differing MRI protocols, the cohort was divided into two groups: one group ( n = 17) underwent musculoskeletal imaging and one group ( n = 3) underwent imaging of the trunk. Overall, MRI-detected bone marrow signal alterations contributed to diagnosis in 20 of 424 (4.7%) newly diagnosed pediatric ALL cases. More than one-third of patients (7/20; 35%) had a completely normal complete blood count (CBC) at presentation. Persistent bone pain was the leading symptom, preceding imaging in 18/20 cases. The mean time from symptom onset to MRI was 20.8 days (range 1–65), while the mean time from MRI to diagnosis was 18.4 days (range 0–180). In the musculoskeletal scans, all patients showed bone marrow signal alterations, predominantly T1-weighted (T1w) hypointensity (17/17) and proton-density-weighted (PDw) or T2-weighted short tau inversion recovery (T2w-STIR) hyperintensity (16/17). In the trunk scans, diffusion-weighted imaging revealed high DWI signal with low ADC values (3/3), and T2-weighted images demonstrated focal lesions (3/3). Conclusion MRI plays an important role in the diagnostic pathway of pediatric ALL, especially in patients with persistent musculoskeletal pain and normal blood counts. In our cohort, MRI examinations could initiate a rapid diagnostic process leading to ALL confirmation. Diffuse T1w hypointensity and diffusion restriction emerged as key imaging findings. A normal CBC should therefore not delay urgent oncologic assessment when the clinical presentation and MRI pattern are suspicious for leukemia.

Abstract Background Medulloblastoma is the most common malignant pediatric brain tumor, typically treated with normofractionated craniospinal irradiation (CSI) with an additional boost over about 6 weeks in children older than 3 years. This study investigates the sensitivity of pediatric medulloblastoma cell lines to different radiation fractionation schedules. While extensively studied in adult tumors, these ratios remain unknown in pediatric cases due to the rarity of the disease. Materials and methods Five distinct medulloblastoma cell lines (ONS76, UW228-3, DAOY, D283, D425) were exposed to varying radiation doses and fractionation schemes. In addition, ONS76 and UW228-3 stably overexpressing MYC were analyzed. Alpha/beta values, representing fractionation sensitivity, were quantified using the linear-quadratic model of radiation survival. Results The study unveiled elevated alpha/beta ratios across diverse medulloblastoma cell lines, with a weighted mean alpha/beta value of 11.01 Gy (CI: 5.23–16.79 Gy). Neither TP53 status nor the levels of MYC expression influenced fractionated radiosensitivity. Furthermore, differences in alpha/beta values cannot be correlated with molecular subgroups (p = 0.07) or radiosensitivity (SF2). Conclusion These in vitro findings strongly recommend normofractionated or hyperfractionated radiotherapy for paediatric medulloblastoma cases due to consistently high alpha/beta values across subgroups. Conversely, hypofractionated radiotherapy is not advisable within a curative approach. This study presents significant potential by enabling the estimation of radiobiological fractionations and dose effects in young, vulnerable patients, highlighting its importance for advancing patient-specific therapeutic strategies.

Background:We assessed clinical features, treatment, and survival of pediatric patients with neurofibromatosis type 1 (NF1) with high-grade glioma (HGG). Methods:Patients from this retrospective cohort study were identified through an international collaborative effort by the SIOPE HGG/DIPG working group. NF1 was diagnosed based on clinical presentation and confirmed by either a pathogenic germline NF1 gene alteration or the exclusion of mismatch repair deficiency. A control cohort without genetic cancer predisposition was matched in a 2:1-ratio from the HIT-HGG database. Results:We identified 29 pediatric patients with NF1-associated HGG. Median age at diagnosis of HGG was 11 years. All but 1 tumor arose outside the optic pathway and included circumscribed and diffuse HGG. Molecular analysis in a subset of tumors identified an enrichment of alterations in CDKN2A, TP53, and ATRX. Event-free and overall survival were as poor as in matched sporadic HGG patients. The prognosis was not superior with upfront radiotherapy compared with delayed radiotherapy. Conclusions:NF1-associated HGGs behave as aggressively as their sporadic counterparts. The relevance of delaying radiotherapy until the time of progression and adjuvant MEK inhibitor treatment needs further investigation.

ABSTRACT:Non-Langerhans cell histiocytoses are a diverse group of histiocytic diseases. Different entities are defined based on clinical, histopathologic, and/or molecular characteristics. This study aimed to define NTRK-rearranged histiocytosis. Through international collaboration, we investigated 50 cases of histiocytosis with pan-tropomyosin receptor kinase (pan-TRK) expression and/or in-frame NTRK rearrangement. We also analyzed 45 control xanthogranulomas using pan-TRK immunohistochemistry and targeted RNA sequencing. Slides were centrally reviewed; clinical and molecular data were collected. The 50 cases comprised 30 children and 20 adults with a median age of 11.5 years (range, 0-73 years) and a male predominance (64%). Most patients (88%) had disease limited to the skin, including a single skin nodule in 41 patients and multiple skin lesions in 3 others. Four newborns presented with skin lesions, hepatomegaly, and thrombocytopenia that required transfusions. The 2 remaining patients had life-threatening lesions of the brain or bronchus. All cases displayed xanthogranuloma histology, often including foamy histiocytes and Touton giant cells. Histiocytes stained positive for pan-TRK in 50 of 50 cases, whereas all 45 control xanthogranulomas without in-frame NTRK fusions stained negative. NTRK1 fusion partners included IRF2BP2 (23/46), TPM3 (12/46), SQSTM1 (3/46), PRDX1 (3/46), NPM1 (2/46), LMNA (2/46), and ARHGEF2 (1/46). Clinical outcomes were favorable, including spontaneous disease regression in 3 of 4 newborns with systemic disease, and rapid clinical response in both patients with a brain or bronchial tumor treated with the TRK inhibitor larotrectinib. This study advances the molecular characterization of histiocytoses and may guide the diagnosis and personalized treatment of patients.

Suppressors of cytokine signaling (SOCS) proteins play a critical role in regulating immune signaling pathways. Deficiency of SOCS1 leads to various autoimmune pathologies. We present two unrelated patients with distinct clinical manifestations. Patient 1, a 16-year-old male from Guinea, presented with Evans Syndrome, musculoskeletal pain and elevated liver enzymes. Patient 2, a 6-year-old German boy, developed recurrent oral aphthous ulcers, mild inflammatory bowel disease and chronic recurrent multifocal osteomyelitis. Both patients were diagnosed with SOCS1 deficiency by genetic testing. Treatment strategies included steroids, JAK inhibition and colchicine. These cases emphasize the importance of considering SOCS1 deficiency in patients with autoimmune or autoinflammatory diseases but also in patients with unexplained elevated IgE levels. They highlight the need for further research in ongoing multicenter registries to better understand this condition.

Background: Neuroblastoma is the most common extracranial solid tumour in children. Relapsed or refractory neuroblastoma is associated with a poor outcome. We assessed the combination of irinotecan-temozolomide and dasatinib-rapamycin (RIST) in patients with relapsed or refractory neuroblastoma. Methods: The multicentre, open-label, randomised, controlled, phase 2, RIST-rNB-2011 trial recruited from 40 paediatric oncology centres in Germany and Austria. Patients aged 1-25 years with high-risk relapsed (defined as recurrence of all stage IV and MYCN amplification stages, after response to treatment) or refractory (progressive disease during primary treatment) neuroblastoma, with Lansky and Karnofsky performance status at least 50%, were assigned (1:1) to RIST (RIST group) or irinotecan-temozolomide (control group) by block randomisation, stratified by MYCN status. We compared RIST (oral rapamycin [loading 3 mg/m(2) on day 1, maintenance 1 mg/m(2) on days 2-4] and oral dasatinib [2 mg/kg per day] for 4 days with 3 days off, followed by intravenous irinotecan [50 mg/m(2) per day] and oral temozolomide [150 mg/m(2) per day] for 5 days with 2 days off; one course each of rapamycin-dasatinib and irinotecan-temozolomide for four cycles over 8 weeks, then two courses of rapamycin-dasatinib followed by one course of irinotecan-temozolomide for 12 weeks) with irinotecan-temozolomide alone (with identical dosing as experimental group). The primary endpoint of progression-free survival was analysed in all eligible patients who received at least one course of therapy. The safety population consisted of all patients who received at least one course of therapy and had at least one post-baseline safety assessment. This trial is registered at ClinicalTrials.gov, NCT01467986, and is closed to accrual. Findings: Between Aug 26, 2013, and Sept 21, 2020, 129 patients were randomly assigned to the RIST group (n=63) or control group (n=66). Median age was 54 years (IQR 37-81). 124 patients (78 [63%] male and 46 [37%] female) were included in the efficacy analysis. At a median follow-up of 72 months (IQR 31-88), the median progression-free survival was 11 months (95% CI 7-17) in the RIST group and 5 months (2-8) in the control group (hazard ratio 062, one-sided 90% CI 081; p=0019). Median progression-free survival in patients with amplified MYCN (n=48) was 6 months (95% CI 4-24) in the RIST group versus 2 months (2-5) in the control group (HR 045 [95% CI 024-084], p=0012); median progression-free survival in patients without amplified MYCN (n=76) was 14 months (95% CI 9-7) in the RIST group versus 8 months (4-15) in the control group (HR 084 [95% CI 051-138], p=049). The most common grade 3 or worse adverse events were neutropenia (54 [81%] of 67 patients given RIST vs 49 [82%] of 60 patients given control), thrombocytopenia (45 [67%] vs 41 [68%]), and anaemia (39 [58%] vs 38 [63%]). Nine serious treatment-related adverse events were reported (five patients given control and four patients given RIST). There were no treatment-related deaths in the control group and one in the RIST group (multiorgan failure). Interpretation: RIST-rNB-2011 demonstrated that targeting of MYCN-amplified relapsed or refractory neuroblastoma with a pathway-directed metronomic combination of a multkinase inhibitor and an mTOR inhibitor can improve progression-free survival and overall survival. This exclusive efficacy in MYCN-amplified, relapsed neuroblastoma warrants further investigation in the first-line setting.

Background Medulloblastoma is the most common malignant pediatric brain tumor, typically treated with normofractionated craniospinal irradiation (CSI) with an additional boost over about 6 weeks in children older than 3 years [1]. This study investigates the sensitivity of pediatric medulloblastoma cell lines to different radiation fractionation schedules. While extensively studied in adult tumors, these ratios remain unknown in pediatric cases due to the rarity of the disease. Materials and Methods Five distinct medulloblastoma cell lines (ONS76, UW228-3, DAOY, D283, D425) were exposed to varying radiation doses and fractionation schemes. In addition, ONS76 and UW2283-3 stably overexpressing MYC were analyzed. Alpha/beta values, representing fractionation sensitivity, were quantified using the linear-quadratic model of radiation survival. Results The study unveiled elevated alpha/beta ratios across diverse medulloblastoma cell lines, with a weighted mean alpha/beta value of 11.01 Gy (CI: 5.23–16.79 Gy). Neither TP53 status nor the levels of MYC expression influenced fractionated radiosensitivity. Furthermore, differences cannot be correlated with molecular subgroups (p = 0,07). Conclusion These in vitro findings strongly recommend normofractionated or hyperfractionated radiotherapy for paediatric medulloblastoma cases due to consistently high Alpha/Beta values across subgroups. Conversely, hypofractionated radiotherapy is not advisable within a curative approach. This study presents significant potential by enabling the estimation of radiobiological fractionations and dose effects in young, vulnerable patients, highlighting its importance for advancing patient-specific therapeutic strategies.

Purpose: We describe a diagnostic procedure suitable for scheduling (re-)vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) according to individual state of humoral immunization. Methods: To clarify the relation between quantitative antibody measurements and humoral ex vivo immune responsiveness, we monitored 124 individuals before, during and six months after vaccination with Spikevax (Moderna, Cambridge, MA, USA). Antibodies against SARS-CoV-2 spike (S1) protein receptor-binding domain (S1-AB) and against nucleocapsid antigens were measured by chemiluminescent immunoassay (Roche). Virus-neutralizing activities were determined by surrogate assays (NeutraLISA, Euroimmune; cPass, GenScript). Neutralization of SARS-CoV-2 in cell culture (full virus NT) served as an ex vivo correlate for humoral immune responsiveness. Results: Vaccination responses varied considerably. Six months after the second vaccination, participants still positive for the full virus NT were safely determined by S1-AB levels ≥1000 U/mL. The full virus NT-positive fraction of participants with S1-AB levels <1000 U/mL was identified by virus-neutralizing activities >70% as determined by surrogate assays (NeutraLISA or cPas). Participants that were full virus NT-negative and presumably insufficiently protected could thus be identified by a sensitivity of >83% and a specificity of >95%. Conclusion: The described diagnostic strategy possibly supports individualized (re-)vaccination schedules based on simple and rapid measurement of serum-based SARS-CoV-2 antibody levels. Our data apply only to WUHAN-type SARS-CoV-2 virus and the current version of the mRNA vaccine from Moderna (Cambridge, MA, USA). Adaptation to other vaccines and more recent SARS-CoV-2 strains will require modification of cut-offs and re-evaluation of sensitivity/specificity.

Purpose: We describe a diagnostic procedure suitable for scheduling (re-)vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) according to individual state of humoral immunization. Methods: To clarify the relation between antibody measurements and immune protection, we monitored 124 individuals before, during and six months after vaccination with Spikevax (Moderna). Antibodies against SARS-CoV-2 spike (S1) protein receptor binding domain (S1-AB) and against nucleocapsid antigen were measured by chemiluminescent immunoassay (Roche). Virus-neutralizing activities were determined by surrogate assays (NeutraLISA, Euroimmune; cPass, GenScript). Neutralization of SARS-CoV-2 in cell culture (full virus NT) served as ex-vivo correlate for humoral immunity. Results: Vaccination responses varied considerably. Six months after 2 nd vaccination, participants still positive for full virus NT were safely discriminated by S1-AB levels ≥1000 U/ml. The full virus NT-positive fraction of participants with S1-AB levels <1000 U/ml was discriminated by virus-neutralizing activities >70 % as determined by surrogate assays (NeutraLISA or cPas). Participants that were full virus NT-negative and therefore presumably insufficiently immune protected could be identified by the above procedure with a sensitivity of >83 % and a specificity of >95 %. Conclusion: In summary, the described diagnostic tool strategy enables individualized (re-)vaccination schedules based on simple and rapid measurement of serum-based SARS-CoV-2 antibody levels. Our data apply only to WUHAN-type SARS-CoV-2 virus and the current version of mRNA vaccine from Moderna. Adaptation to other vaccines and more recent SARS-CoV-2 strains will require modification of cut-offs and re-evaluation of sensitivity/specificity. Study numbers: 2021-1455 and 2020-1259_1, Ethics Committee Med. Fac. HHU.

Similar to pediatric acute myeloid leukemia (AML) the subgroup of biphenotypic acute lymphoblastic leukemia (ALL) is a rare complex entity with adverse outcome, characterized by the surface expression of CD33. Despite novel and promising anti-CD19 targeted immunotherapies such as chimeric antigen receptor T cells and bispecific anti-CD19/CD3 antibodies, relapse and resistance remain a major challenge in about 30% to 60% of patients. To investigate the potential role of the fully humanized bispecific antibody CD16 × CD33 (BiKE) in children with CD33+ acute leukemia, we tested whether the reagent was able to boost NK cell effector functions against CD33+ AML and biphenotypic ALL blasts. Stimulation of primary NK cells from healthy volunteers with 16 × 33 BiKE led to increased cytotoxicity, degranulation and cytokine production against CD33+ cell lines. Moreover, BiKE treatment significantly increased degranulation, IFN-γ and TNF-α production against primary ALL and AML targets. Importantly, also NK cells from leukemic patients profited from restoration of effector functions by BiKE treatment, albeit to a lesser extent than NK cells from healthy donors. In particular, those patients with low perforin and granzyme expression showed compromised cytotoxic function even in the presence of BiKE. In patients with intrinsic NK cell deficiency, combination therapy of CD16xCD33 BiKE and allogeneic NK cells might thus be a promising therapeutic approach. Taken together, CD16xCD33 BiKE successfully increased NK cell effector functions against pediatric AML and biphenotypic ALL blasts and constitutes a promising new option for supporting maintenance therapy or “bridging” consolidation chemotherapy before hematopoietic stem cell transplantation.

Purpose Deficiency of adenosine deaminase 2 (DADA2) is an inherited inborn error of immunity, characterized by autoinflammation (recurrent fever), vasculopathy (livedo racemosa, polyarteritis nodosa, lacunar ischemic strokes, and intracranial hemorrhages), immunodeficiency, lymphoproliferation, immune cytopenias, and bone marrow failure (BMF). Tumor necrosis factor (TNF-α) blockade is the treatment of choice for the vasculopathy, but often fails to reverse refractory cytopenia. We aimed to study the outcome of hematopoietic cell transplantation (HCT) in patients with DADA2. Methods We conducted a retrospective study on the outcome of HCT in patients with DADA2. The primary outcome was overall survival (OS). Results Thirty DADA2 patients from 12 countries received a total of 38 HCTs. The indications for HCT were BMF, immune cytopenia, malignancy, or immunodeficiency. Median age at HCT was 9 years (range: 2–28 years). The conditioning regimens for the final transplants were myeloablative ( n = 20), reduced intensity ( n = 8), or non-myeloablative ( n = 2). Donors were HLA-matched related ( n = 4), HLA-matched unrelated ( n = 16), HLA-haploidentical ( n = 2), or HLA-mismatched unrelated ( n = 8). After a median follow-up of 2 years (range: 0.5–16 years), 2-year OS was 97%, and 2-year GvHD-free relapse-free survival was 73%. The hematological and immunological phenotypes resolved, and there were no new vascular events. Plasma ADA2 enzyme activity normalized in 16/17 patients tested. Six patients required more than one HCT. Conclusion HCT was an effective treatment for DADA2, successfully reversing the refractory cytopenia, as well as the vasculopathy and immunodeficiency. Clinical Implications HCT is a definitive cure for DADA2 with > 95% survival.

Survival of patients with pediatric acute lymphoblastic leukemia (ALL) after allogeneic hematopoietic stem cell transplantation (allo-SCT) is mainly compromised by leukemia relapse, carrying dismal prognosis. As novel individualized therapeutic approaches are urgently needed, we performed whole-exome sequencing of leukemic blasts of 10 children with post-allo-SCT relapses with the aim of thoroughly characterizing the mutational landscape and identifying druggable mutations. We found that post-allo-SCT ALL relapses display highly diverse and mostly patient-individual genetic lesions. Moreover, mutational cluster analysis showed substantial clonal dynamics during leukemia progression from initial diagnosis to relapse after allo-SCT. Only very few alterations stayed constant over time. This dynamic clonality was exemplified by the detection of thiopurine resistance-mediating mutations in the nucleotidase NT5C2 in 3 patients' first relapses, which disappeared in the post-allo-SCT relapses on relief of selective pressure of maintenance chemotherapy. Moreover, we identified TP53 mutations in 4 of 10 patients after allo-SCT, reflecting acquired chemoresistance associated with selective pressure of prior antineoplastic treatment. Finally, in 9 of 10 children's post-allo-SCT relapse, we found alterations in genes for which targeted therapies with novel agents are readily available. We could show efficient targeting of leukemic blasts by APR-246 in 2 patients carrying TP53 mutations. Our findings shed light on the genetic basis of post-allo-SCT relapse and may pave the way for unraveling novel therapeutic strategies in this challenging situation.

Although allogeneic hematopoietic stem-cell transplantation (HSCT) provides high cure rates for children with high-risk acute lymphoblastic leukaemia (ALL), relapses remain the main cause of treatment failure. Whereas donor killer cell immunoglobulin-like receptor (KIR) genotype was shown to impact on relapse incidence in adult myeloid leukaemia similar studies in paediatric ALL are largely missing. Effect of donor KIR genotype on transplant outcome was evaluated in 317 children receiving a first myeloablative HSCT from an HLA-matched unrelated donor or sibling within the prospective ALL-SCT-BFM-2003 trial. Analysis of donor KIR gene polymorphism revealed that centromeric presence and telomeric absence of KIR B haplotypes was associated with reduced relapse risk. A centromeric/telomeric KIR score (ct-KIR score) integrating these observations correlated with relapse risk (hazard ratio (HR) 0.58; P = 0.002) while it had no impact on graft-versushost disease or non-relapse mortality. In multivariable analyses ct-KIR score was associated with reduced relapse risk (HR 0.58; P = 0.003) and a trend towards improved event-free survival (HR 0.76; P = 0.059). This effect proved independent of MRD level prior to HSCT. Our data suggest that in children with ALL undergoing HSCT after myeloablative conditioning, donor selection based on KIR genotyping holds promise to improve clinical outcome by decreasing relapse risk and prolonged event-free survival.

Here, we report the case of severe adenoviremia in a 7-year-old boy with highly-resistant, acute leukemia. A combined approach of αβTCR-CD19-depleted stem cell transplantation, enabling immunosuppression-free post-transplant care, and early transfer of adenovirus-specific donor T cells during aplasia resulted in rapid and complete clearance of the treatment-refractory adenoviremia.

Background: Intraventricular hemorrhage (IVH) is one of the most formidable neurological complications in premature infants. Low grade IVH is often regarded as a low risk factor for long-term neurological impairment. Methods: We retrospectively investigated, if there was an association of low IVH grade and adverse neurological outcome in survivors at 20-24 months of corrected age. Results: 89 infants, median gestational age 27 + 4, were included in the study. In total 55 children with IVH grade I (n = 34) or grade II (n = 21), plus 34 children with IVH grade III (n = 13) and IVH grad IV (n = 21) were included. In infants with grade I and II IVH median mental developmental index (MDI) and psychomotor developmental index (PDI) were 90 and 88, respectively. In total 18 children (33%) had a MDI one standard deviation below the mean ( < 85, < 1SD). 9 out of these 18 had an IVH grade I. 17 infants (31%) had a PDI < 1SD. An MDI/PDI < 2SD was only found in 7 (13%)/6 (11%) children, respectively. Regression analysis showed that IVH grade (p < 0,001) and gestational age (p = 0,008) were significant independent risk factors for an adverse motoric outcome. Conclusion: Our collective revealed that an IVH grade I was not always associated with a good outcome. Interpretation and prediction of long outcome prognosis after IVH grade I or II requires careful consideration as it might be associated with increased disability.

Heat shock protein 90 (HSP90) stabilizes many client proteins, including the BCR-ABL1 oncoprotein. BCR-ABL1 is the hallmark of chronic myeloid leukemia (CML) in which treatment-free remission (TFR) is limited, with clinical and economic consequences. Thus, there is an urgent need for novel therapeutics that synergize with current treatment approaches. Several inhibitors targeting the N-terminal domain of HSP90 are under investigation, but side effects such as induction of the heat shock response (HSR) and toxicity have so far precluded their US Food and Drug Administration approval. We have developed a novel inhibitor (aminoxyrone [AX]) of HSP90 function by targeting HSP90 dimerization via the C-terminal domain. This was achieved by structure-based molecular design, chemical synthesis, and functional preclinical in vitro and in vivo validation using CML cell lines and patient-derived CML cells. AX is a promising potential candidate that induces apoptosis in the leukemic stem cell fraction (CD34+CD38-) as well as the leukemic bulk (CD34+CD38+) of primary CML and in tyrosine kinase inhibitor (TKI)-resistant cells. Furthermore, BCR-ABL1 oncoprotein and related pro-oncogenic cellular responses are downregulated, and targeting the HSP90 C terminus by AX does not induce the HSR in vitro and in vivo. We also probed the potential of AX in other therapy-refractory leukemias. Therefore, AX is the first peptidomimetic C-terminal HSP90 inhibitor with the potential to increase TFR in TKI-sensitive and refractory CML patients and also offers a novel therapeutic option for patients with other types of therapy-refractory leukemia because of its low toxicity profile and lack of HSR.