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Germline SAMD9 and SAMD9L mutations ( SAMD9/9L mut ) predispose to myelodysplastic syndromes (MDS) with propensity for somatic rescue. In this study, we investigated a clinically annotated pediatric MDS cohort ( n  = 669) to define the prevalence, genetic landscape, phenotype, therapy outcome and clonal architecture of SAMD9/9L syndromes. In consecutively diagnosed MDS, germline SAMD9/9L mut accounted for 8% and were mutually exclusive with GATA2 mutations present in 7% of the cohort. Among SAMD9/9L mut cases, refractory cytopenia was the most prevalent MDS subtype (90%); acquired monosomy 7 was present in 38%; constitutional abnormalities were noted in 57%; and immune dysfunction was present in 28%. The clinical outcome was independent of germline mutations. In total, 67 patients had 58 distinct germline SAMD9/9L mut clustering to protein middle regions. Despite inconclusive in silico prediction, 94% of SAMD9/9L mut suppressed HEK293 cell growth, and mutations expressed in CD34 +  cells induced overt cell death. Furthermore, we found that 61% of SAMD9/9L mut patients underwent somatic genetic rescue (SGR) resulting in clonal hematopoiesis, of which 95% was maladaptive (monosomy 7 ± cancer mutations), and 51% had adaptive nature (revertant UPD7q, somatic SAMD9/9L mut ). Finally, bone marrow single-cell DNA sequencing revealed multiple competing SGR events in individual patients. Our findings demonstrate that SGR is common in SAMD9/9L mut MDS and exemplify the exceptional plasticity of hematopoiesis in children. This analysis of a large, clinically annotated cohort of individuals with predisposition to myelodysplastic syndromes reveals insights into the genetic determinants of disease progression and their relationship with clinical manifestations and therapy outcome.

Background: Febrile neutropenia (FN) is a common and potentially life-threatening complication in pediatric oncology. Rapid initiation of empiric antibiotics is critical to improving prognosis. This study evaluated the impact of simple changes to a standard operating procedure (SOP) for FN treatment on the time-to-antibiotic (TTA) in pediatric cancer patients, as well as potential clinical effects. Methods: In this retrospective, single-center, cohort study, children with cancer presenting with FN at the emergency room (pedER) or oncology outpatient department (OD) were included over two one-year periods—before and after SOP adaption. The revised SOP defined a target TTA of ≤30 min. The primary endpoint was to compare median TTA and the proportion of FN episodes meeting target TTA. Secondary endpoints comprised adverse events (AEs) (e.g., ICU admission, need for respiratory or circulatory support, sepsis criteria). Results: After SOP adaption, 32.9% of episodes met target TTA, up from 5.9% before. Median TTA was significantly reduced (44 min vs. 93 min). The improvement persisted during the study period. AE rates showed no significant change. Conclusions: Simple procedural adjustments may significantly improve quality indicators of care, e.g., reducing TTA in pediatric FN patients. These adjustments may be transferable to other pediatric oncology settings.

It is well established that somatic genomic changes can influence phenotypes in cancer, but the role of adaptive changes in developmental disorders is less well understood. Here we have used next-generation sequencing approaches to identify de novo heterozygous mutations in sterile α motif domain-containing protein 9 (SAMD9, located on chromosome 7q21.2) in 8 children with a multisystem disorder termed MIRAGE syndrome that is characterized by intrauterine growth restriction (IUGR) with gonadal, adrenal, and bone marrow failure, predisposition to infections, and high mortality. These mutations result in gain of function of the growth repressor product SAMD9. Progressive loss of mutated SAMD9 through the development of monosomy 7 (-7), deletions of 7q (7q-), and secondary somatic loss-of-function (nonsense and frameshift) mutations in SAMD9 rescued the growth-restricting effects of mutant SAMD9 proteins in bone marrow and was associated with increased length of survival. However, 2 patients with -7 and 7q- developed myelodysplastic syndrome, most likely due to haploinsufficiency of related 7q21.2 genes. Taken together, these findings provide strong evidence that progressive somatic changes can occur in specific tissues and can subsequently modify disease phenotype and influence survival. Such tissue-specific adaptability may be a more common mechanism modifying the expression of human genetic conditions than is currently recognized.

While survival has improved for Burkitt lymphoma patients, potential differences in outcome between pediatric and adult patients remain unclear. In both age groups, survival remains poor at relapse. Therefore, we conducted a comparative study in a large pediatric cohort, including 191 cases and 97 samples from adults. While TP53 and CCND3 mutation frequencies are not age related, samples from pediatric patients showed a higher frequency of mutations in ID3 , DDX3X, ARID1A and SMARCA4 , while several genes such as BCL2 and YY1AP1 are almost exclusively mutated in adult patients. An unbiased analysis reveals a transition of the mutational profile between 25 and 40 years of age. Survival analysis in the pediatric cohort confirms that TP53 mutations are significantly associated with higher incidence of relapse (25 ± 4% versus 6 ± 2%, p-value 0.0002). This identifies a promising molecular marker for relapse incidence in pediatric BL which will be used in future clinical trials. Survival outcomes in Burkitt lymphoma differ between adult and paediatric patients. Here, the authors show differences in mutational frequencies between age groups, and a transition between mutational profiles which occurs between 25 and 40 years.

Diamond Blackfan anemia (DBA) is a rare congenital syndrome presenting primarily as pure red cell aplasia with constitutional abnormalities and cancer predisposition. Established treatment options are corticosteroids, regular erythrocyte transfusions with iron chelation therapy, and hematopoietic stem cell transplantation (HSCT). To date, HSCT is the only definitive curative treatment for the hematological phenotype of DBA, but there is little experience with its use. Given the rarity of the disease and its unique features, an expert panel agreed to draw up a set of recommendations on the use of HSCT in DBA to guide clinical decision-making and practice. The recommendations address indications, pretransplant patient evaluation, donor selection, stem cell sources, conditioning regimens, prophylaxis of rejection and graft versus host disease, and post-transplant follow-up.

GATA2 deficiency is a heterogeneous multi-system disorder characterized by a high risk of developing myelodysplastic syndrome (MDS) and myeloid leukemia. We analyzed the outcome of 65 patients reported to the registry of the European Working Group (EWOG) of MDS in childhood carrying a germline GATA2 mutation (GATA2mut) who had undergone hematopoietic stem cell transplantation (HSCT). At 5 years the probability of overall survival and disease-free survival (DFS) was 75% and 70%, respectively. Non-relapse mortality and relapse equally contributed to treatment failure. There was no evidence of increased incidence of graft-versus-host-disease or excessive rates of infections or organ toxicities. Advanced disease and monosomy 7 (−7) were associated with worse outcome. Patients with refractory cytopenia of childhood (RCC) and normal karyotype showed an excellent outcome (DFS 90%) compared to RCC and −7 (DFS 67%). Comparing outcome of GATA2mut with GATA2wt patients, there was no difference in DFS in patients with RCC and normal karyotype. The same was true for patients with −7 across morphological subtypes. We demonstrate that HSCT outcome is independent of GATA2 germline mutations in pediatric MDS suggesting the application of standard MDS algorithms and protocols. Our data support considering HSCT early in the course of GATA2 deficiency in young individuals.

Deficiency of the transcription factor GATA2 is a highly penetrant genetic disorder predisposing to myelodysplastic syndromes (MDS) and immunodeficiency. It has been recognized as the most common cause underlying primary MDS in children. Triggered by the discovery of a recurrent synonymous GATA2 variant, we systematically investigated 911 patients with phenotype of pediatric MDS or cellular deficiencies for the presence of synonymous alterations in GATA2. In total, we identified nine individuals with five heterozygous synonymous mutations: c.351C>G, p.T117T (N = 4); c.649C>T, p.L217L; c.981G>A, p.G327G; c.1023C>T, p.A341A; and c.1416G>A, p.P472P (N = 2). They accounted for 8.2% (9/110) of cases with GATA2 deficiency in our cohort and resulted in selective loss of mutant RNA. While for the hotspot mutation (c.351C>G) a splicing error leading to RNA and protein reduction was identified, severe, likely late stage RNA loss without splicing disruption was found for other mutations. Finally, the synonymous mutations did not alter protein function or stability. In summary, synonymous GATA2 substitutions are a new common cause of GATA2 deficiency. These findings have broad implications for genetic counseling and pathogenic variant discovery in Mendelian disorders.

AML SCT-BFM 2007 was the first hematopoietic stem cell transplantation (HCT) trial in Germany to comply with the European Clinical Trials Directive, and aimed to standardize pediatric HCT for acute myeloid leukemia (AML) across centers in Germany, Austria, and the Czech Republic. Children with high-risk features and a good early response achieving a complete first remission (CR-1) and those in CR-2 after a first relapse were stratified to receive HCT from a matched donor after myeloablative conditioning consisting of busulfan, cyclophosphamide, and melphalan. Four-year EFS and OS were 61 and 70%. Cumulative incidence of relapse (CIR) was 22%. TRM was 15% and correlated with age reaching 9% (SE 3%) in children younger than 12 years and 31% (SE 9%) in older children and adolescents. Children with poorly responding primary disease or relapse were allocated to receive early HCT after a cytoreductive regimen with fludarabine, amsacrine, and cytarabine, followed by reduced intensity conditioning and prophylactic donor lymphocyte infusions. Four-year EFS and OS were 49 and 53%. CIR was 38% and TRM 11%. For patients with primary poor response disease, early use of RIC HCT followed by prophylactic DLI can induce long-term remissions in more than 50% (EFS 46% (SE 9%)).

Anti-CD19 chimeric antigen receptor T cells (CAR) are a well-established treatment option for children and young adults suffering from relapsed/refractory B-lineage acute lymphoblastic leukemia. Bridging therapy is used to control disease prior to start of lymphodepletion before CAR infusion and thereby improve efficacy of CAR therapy. However, the effect of different bridging strategies on outcome, side effects and response to CAR therapy is still poorly understood. In this retrospective, multinational study, real-world data were collected from 14 different sites in Germany, Austria and Switzerland on 88 patients receiving 93 2nd-generation CAR therapies. Bridging therapy was classified into the categories 1) no systemic therapy (15/93 treatments), 2) low-intensity therapy (38/93 treatments) and 3) high-intensity therapy (39/93 treatments). We analyzed the impact of bridging regimens on clinical outcome. Patients receiving a high-intensity bridging therapy had a significantly higher tumor burden at time of eligibility compared to patients treated with a low-intensity or no systemic bridging therapy. They suffered significantly more from bacterial adverse events and mucositis. Overall survival was significantly better for patients who did not receive any bridging therapy in comparison to patients who had been treated with a low- or high-intensity bridging regimen. In conclusion, in this retrospective cohort, high-intensity bridging therapy has not improved the outcome in terms of overall and progression-free survival in comparison to a low-intensity therapy. Yet, high-intensity bridging therapy was associated with more adverse events. Our study suggests that a low-intensity bridging regimen may be preferred whenever tumor burden and disease kinetics allow this treatment strategy.