Outcomes of hematopoietic stem cell transplantation in 813 pediatric patients with Fanconi anemia.

ABSTRACT: Allogeneic hematopoietic stem cell transplantation (HSCT) is the only established curative option for Fanconi anemia (FA)-associated bone marrow failure (BMF)/aplastic anemia (AA) and acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS). We performed a retrospective multicenter study on 813 children with FA undergoing first HSCT between 2010 and 2018. Median duration of follow-up was 3.7 years. Median age at transplant was 8.8 years (IQR, 6.5-18.1). Five-year overall survival (OS), event-free survival (EFS), and graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS) were 83% (95% confidence interval [CI], 80-86), 78% (95% CI, 75-81), and 70% (95% CI, 67-74), respectively. OS was comparable between matched family donor (MFD; n = 441, 88%) and matched unrelated donor (MUD; n = 162, 86%) and was superior to that of mismatched family donor (MMFD) or mismatched unrelated donor (MMUD; n = 144, 72%) and haploidentical donor (HID; n = 66, 70%; P < .001). In multivariable analysis, a transplant indication of AML/MDS (vs AA/BMF), use of MMFD/MMUD and HID (vs MFD), and fludarabine-cyclophosphamide (FluCy) plus other conditioning (vs FluCy) independently predicted inferior OS, whereas alemtuzumab vs antithymocyte globulin was associated with better OS. Age ≥10 years was associated with worse EFS and GRFS. Cumulative incidences (CINs) of primary and secondary graft failure were 2% and 3% respectively. CINs of grade 3 to 4 acute GVHD and chronic GVHD were 12% and 8% respectively. The 5-year CIN of secondary malignancy was 2%. These data suggest that HSCT should be offered to patients with FA with AA/BMF at a younger age in the presence of a well-matched donor.

Alternative donor transplantation for severe aplastic anemia: a comparative study of the SAAWP EBMT.

ABSTRACT: Selecting the most suitable alternative donor becomes challenging in severe aplastic anemia (SAA) when a matched sibling donor (MSD) is unavailable. We compared outcomes in patients with SAA undergoing stem cell transplantation (SCT) from matched unrelated donors (MUD) (n = 1106), mismatched unrelated donors (MMUD) (n = 340), and haploidentical donors (Haplo) (n = 206) registered in the European Society for Blood and Marrow Transplantation database (2012-2021). For Haplo SCT, only those receiving posttransplant cyclophosphamide for graft-versus-host disease (GVHD) prophylaxis were included. Median age was 20 years, and the median time from diagnosis to transplantation 8.7 months. Compared with MUD, MMUD (hazard ratio [HR], 2.93; 95% confidence interval [CI], 1.52-5.6) and Haplo (HR, 5.15; 95% CI, 2.5-10.58) showed significantly higher risks of primary graft failure. MUD had lower rates of acute GVHD compared with MMUD and Haplo (grade 2-4: 13%, 22%, and 19%, respectively; P < .001; grade 3-4: 5%, 9%, and 7%, respectively; P = .028). The 3-year nonrelapse mortality rate was 14% for MUD, 19% for MMUD, and 27% for Haplo (P < .001), whereas overall survival and GVHD and relapse-free survival (GRFS) rates were 81% and 73% for MUD, 74% and 65% for MMUD, and 63% and 54% for Haplo, respectively (P < .001). In addition to donor type, multivariable analysis identified other factors associated with GRFS such as patient age, performance status, and interval between diagnosis and transplantation. For patients with SAA lacking an MSD, our findings support MUDs as the preferable alternative donor option. However, selecting between an MMUD and Haplo donor remains uncertain and requires further exploration.

Hematopoietic Stem Cell Transplantation for C1q Deficiency: A Study on Behalf of the EBMT Inborn Errors Working Party.

C1q deficiency is a rare inborn error of immunity characterized by increased susceptibility to infections and autoimmune manifestations mimicking SLE, with an associated morbidity and mortality. Because C1q is synthesized by monocytes, to date, four patients treated with allogeneic HSCT have been reported, with a positive outcome in three. We conducted an international retrospective study to assess the outcome of HSCT in C1q deficiency. Eighteen patients, fourteen previously unreported, from eleven referral centres, were included. Two patients had two HSCTs, thus 20 HSCTs were performed in total, at a median age of 10 years (range 0.9-19). Indications for HSCT were autoimmune manifestations not controlled by ongoing treatment in seventeen, and early development of MALT lymphoma in one patient. Overall survival (OS) was 71% and event-free survival was 59% at two years (considering an event as acute GvHD ≥ grade III, disease recurrence and death). In eleven patients HSCT led to resolution of autoimmune features and discontinuation of immunosuppressive treatments (follow-up time range 3-84 months). Five patients died due to transplant-related complications. Patients with a severe autoimmune phenotype, defined as neurological and/or renal involvement, had the worst OS (40% vs 84%; p = 0.034). Reviewing data of 69 genetically confirmed C1q deficient patients, we found that anti-Ro antibodies are associated with neurologic involvement, and anti-RNP and anti-DNA antibodies with renal involvement. In conclusion, HSCT may be a valid curative option for C1q deficiency, but careful selection of patients, with an accurate assessment of risk and benefit, is mandatory.

CTP synthase 1 deficiency in humans reveals its central role in lymphocyte proliferation.

Lymphocyte functions triggered by antigen recognition and co-stimulation signals are associated with a rapid and intense cell division, and hence with metabolism adaptation. The nucleotide cytidine 5' triphosphate (CTP) is a precursor required for the metabolism of DNA, RNA and phospholipids. CTP originates from two sources: a salvage pathway and a de novo synthesis pathway that depends on two enzymes, the CTP synthases (or synthetases) 1 and 2 (CTPS1 with CTPS2); the respective roles of these two enzymes are not known. CTP synthase activity is a potentially important step for DNA synthesis in lymphocytes. Here we report the identification of a loss-of-function homozygous mutation (rs145092287) in CTPS1 in humans that causes a novel and life-threatening immunodeficiency, characterized by an impaired capacity of activated T and B cells to proliferate in response to antigen receptor-mediated activation. In contrast, proximal and distal T-cell receptor (TCR) signalling events and responses were only weakly affected by the absence of CTPS1. Activated CTPS1-deficient cells had decreased levels of CTP. Normal T-cell proliferation was restored in CTPS1-deficient cells by expressing wild-type CTPS1 or by addition of exogenous CTP or its nucleoside precursor, cytidine. CTPS1 expression was found to be low in resting T cells, but rapidly upregulated following TCR activation. These results highlight a key and specific role of CTPS1 in the immune system by its capacity to sustain the proliferation of activated lymphocytes during the immune response. CTPS1 may therefore represent a therapeutic target of immunosuppressive drugs that could specifically dampen lymphocyte activation.

Successful Management of Hepatosplenic Infection Due to Saccharomyces cerevisiae in a Child With Acute Lymphoblastic Leukemia.

Saccharomyces cerevisiae is an emerging pathogen within the immunocompromised. We present a 4-year-old boy with acute lymphoblastic leukemia presenting with polymerase chain reaction-confirmed hepatosplenic S. cerevisiae infection and significant immune reconstitution symptoms. We explore the challenges of monitoring treatment efficacy using C-Reactive protein, ß-D-glucan, and imaging and the administration of chemotherapy alongside antifungals and steroids for control of immune reconstitution syndrome.

Multicenter phase 1/2 application of adenovirus-specific T cells in high-risk pediatric patients after allogeneic stem cell transplantation.

BACKGROUND: Adenovirus (ADV) reactivation can cause significant morbidity and mortality in children after allogeneic stem cell transplantation. Antiviral drugs can control viremia, but viral clearance requires recovery of cell-mediated immunity. METHOD: This study was an open-label phase 1/2 study to investigate the feasibility of generating donor-derived ADV-specific T cells (Cytovir ADV, Cell Medica) and to assess the safety of pre-emptive administration of ADV-specific T cells in high-risk pediatric patients after allogeneic hematopoietic stem cell transplantation (HSCT) to treat adenoviremia. Primary safety endpoints included graft-versus-host disease (GvHD), and secondary endpoints determined antiviral responses and use of antiviral drugs. RESULTS: Between January 2013 and May 2016, 92 donors were enrolled for the production of ADV T cells at three centers in the United Kingdom (UK), and 83 products were generated from 72 mobilized peripheral blood harvests and 20 steady-state whole blood donations. Eight children received Cytovir ADV T cells after standard therapy and all resolved ADV viremia between 15 and 127 days later. ADV-specific T cells were detectable using enzyme-linked immunospot assay (ELISpot) in the peripheral blood of all patients analyzed. Serious adverse events included Grade II GvHD, Astrovirus encephalitis and pancreatitis. CONCLUSION: The study demonstrates the safety and feasibility of pre-emptively manufacturing peptide pulsed ADV-specific cells for high-risk pediatric patients after transplantation and provides early evidence of clinical efficacy.

Long-term outcome of Hurler syndrome patients after hematopoietic cell transplantation: an international multicenter study.

Mucopolysaccharidosis type I-Hurler syndrome (MPS-IH) is a lysosomal storage disease characterized by multisystem morbidity and death in early childhood. Although hematopoietic cell transplantation (HCT) has been performed in these patients for more than 30 years, large studies on the long-term outcome of patients with MPS-IH after HCT are lacking. The goal of this international study was to identify predictors of the long-term outcome of patients with MPS-IH after successful HCT. Two hundred seventeen patients with MPS-IH successfully engrafted with a median follow-up age of 9.2 years were included in this retrospective analysis. Primary endpoints were neurodevelopmental outcomes and growth. Secondary endpoints included neurologic, orthopedic, cardiac, respiratory, ophthalmologic, audiologic, and endocrinologic outcomes. Considerable residual disease burden was observed in the majority of the transplanted patients with MPS-IH, with high variability between patients. Preservation of cognitive function at HCT and a younger age at transplantation were major predictors for superior cognitive development posttransplant. A normal α-l-iduronidase enzyme level obtained post-HCT was another highly significant predictor for superior long-term outcome in most organ systems. The long-term prognosis of patients with MPS-IH receiving HCT can be improved by reducing the age at HCT through earlier diagnosis, as well as using exclusively noncarrier donors and achieving complete donor chimerism.

Haematopoietic stem cell transplantation in inborn errors of metabolism.

PURPOSE OF REVIEW: This review summarizes the main results of haematopoietic stem cell transplantation (HSCT) in selected inborn errors of metabolism (IEMs). RECENT FINDINGS: Early diagnosis and immediate referral to an IEM specialist is of paramount importance to improve clinical outcome: patients who are transplanted early or in their presymptomatic phase generally achieve better correction of their somatic symptoms and neurocognitive development. Long-term outcome in children with Hurler syndrome is influenced by age at HSCT, baseline clinical status and post-HSCT enzyme levels. Myeloablative Busulfan-based conditioning regimens with therapeutic drug monitoring are recommended to achieve full donor engraftment and more robust enzyme delivery after HSCT. Gene therapy can lead to production of supranormal enzyme levels, and preliminary clinical results are also promising in IEMs historically not responsive to allogeneic HSCT. SUMMARY: Allogeneic HSCT has largely contributed to the improved survival and quality of life of many children affected by IEMs. Neonatal screening could enable earlier HSCT, and this might significantly reduce residual disease burden and improve clinical outcome. Novel strategies, such as gene therapy, have shown encouraging clinical results in selected IEMs and might become more widely available in the future, with potentially better enzyme delivery and reduced transplant-related toxicity.

BCSH/BSBMT/UK clinical virology network guideline: diagnosis and management of common respiratory viral infections in patients undergoing treatment for haematological malignancies or stem cell transplantation.

A joint working group established by the Haemato-oncology subgroup of the British Committee for Standards in Haematology, the British Society for Bone Marrow Transplantation and the UK Clinical Virology Network has reviewed the available literature and made recommendations for the diagnosis and management of respiratory viral infections in patients with haematological malignancies or those undergoing haematopoietic stem cell transplantation. This guideline includes recommendations for the diagnosis, prevention and treatment of respiratory viral infections in adults and children. The suggestions and recommendations are primarily intended for physicians practising in the United Kingdom.

Enzyme replacement therapy prior to haematopoietic stem cell transplantation in Mucopolysaccharidosis Type I: 10 year combined experience of 2 centres.

Haematopoietic stem cell transplantation is the treatment of choice for the severe form of Mucopolysaccharidosis Type I, or Hurler syndrome. In many centres standard practice is to deliver enzyme replacement therapy alongside haematopoietic stem cell transplantation to improve the condition of the patient prior to transplant. We report the combined 10 year experience of this approach in two paediatric metabolic and transplant centres. Of 81 patients who underwent a first transplant procedure for Hurler, 88% (71/81) survived and 81% (66/81) were alive and engrafted at a median follow-up of 46 months (range 3-124 months). The incidence of grade II-IV acute and any chronic graft versus host disease was 17% and 11% respectively. Urinary glycosaminoglycans were significantly reduced after a period of enzyme replacement therapy, and further reductions were seen at 13-24 months and 25+months after transplantation. In several individuals with decreased cardiac contractility, an improvement of their condition during enzyme replacement therapy enabled them to undergo transplantation, with one individual receiving full intensity conditioning.

Mutations in TRNT1 cause congenital sideroblastic anemia with immunodeficiency, fevers, and developmental delay (SIFD).

Mutations in genes encoding proteins that are involved in mitochondrial heme synthesis, iron-sulfur cluster biogenesis, and mitochondrial protein synthesis have previously been implicated in the pathogenesis of the congenital sideroblastic anemias (CSAs). We recently described a syndromic form of CSA associated with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD). Here we demonstrate that SIFD is caused by biallelic mutations in TRNT1, the gene encoding the CCA-adding enzyme essential for maturation of both nuclear and mitochondrial transfer RNAs. Using budding yeast lacking the TRNT1 homolog, CCA1, we confirm that the patient-associated TRNT1 mutations result in partial loss of function of TRNT1 and lead to metabolic defects in both the mitochondria and cytosol, which can account for the phenotypic pleiotropy.

Heparan sulfate inhibits hematopoietic stem and progenitor cell migration and engraftment in mucopolysaccharidosis I.

Mucopolysaccharidosis I Hurler (MPSI-H) is a pediatric lysosomal storage disease caused by genetic deficiencies in IDUA, coding for α-l-iduronidase. Idua(-/-) mice share similar clinical pathology with patients, including the accumulation of the undegraded glycosaminoglycans (GAGs) heparan sulfate (HS), and dermatan sulfate (DS), progressive neurodegeneration, and dysostosis multiplex. Hematopoietic stem cell transplantation (HSCT) is the most effective treatment for Hurler patients, but reduced intensity conditioning is a risk factor in transplantation, suggesting an underlying defect in hematopoietic cell engraftment. HS is a co-receptor in the CXCL12/CXCR4 axis of hematopoietic stem and progenitor cell (HSPC) migration to the bone marrow (BM), but the effect of HS alterations on HSPC migration, or the functional role of HS in MPSI-H are unknown. We demonstrate defective WT HSPC engraftment and migration in Idua(-/-) recipient BM, particularly under reduced intensity conditioning. Both intra- but especially extracellular Idua(-/-) BM HS was significantly increased and abnormally sulfated. Soluble heparinase-sensitive GAGs from Idua(-/-) BM and specifically 2-O-sulfated HS, elevated in Idua(-/-) BM, both inhibited CXCL12-mediated WT HSPC transwell migration, while DS had no effect. Thus we have shown that excess overly sulfated extracellular HS binds, and sequesters CXCL12, limiting hematopoietic migration and providing a potential mechanism for the limited scope of HSCT in Hurler disease.

Hematopoietic cell transplantation for mucopolysaccharidosis patients is safe and effective: results after implementation of international guidelines.

Allogeneic hematopoietic cell transplantation (HCT) is the only treatment able to prevent progressive neurodegenerative disease in a selected group of mucopolysaccharidosis (MPS) disorders. However, its use was historically limited by the high risk of graft failure and transplantation-related morbidity and mortality. Therefore, since 2005 new international HCT guidelines for MPS disorders were proposed. The survival and graft outcomes of MPS patients receiving HCT according to these guidelines in 2 European centers of expertise were evaluated. Two consecutive conditioning regimens were used, busulfan/cyclophosphamide or fludarabine/busulfan-based, both with exposure-targeted i.v. busulfan. A noncarrier matched sibling donor (MSD), matched unrelated cord blood (UCB), or matched unrelated donor (MUD) were considered to be preferred donors. If not available, a mismatched UCB donor was used. Participants were 62 MPS patients (56 MPS type I-Hurler, 2 MPS type II, 2 MPS type III, and 2 MPS type VI) receiving HCT at median age 13.5 months (range, 3 to 44). Forty-one patients received a UCB donor, 17 MSD, and 4 MUD. High overall survival (95.2%) and event-free survival (90.3%) were achieved with only low toxicity: 13.3% acute graft-versus-host disease aGVHD) grades II to IV and 14.8% chronic GVHD (1.9% extensive). A mismatched donor predicted for lower event-free survival (P = .04). A higher age at HCT was a predictor for both aGVHD (P = .001) and chronic GVHD (P = .01). The use of a mismatched donor was a predictor for aGVHD (P = .01). Higher rates of full-donor chimerism were achieved in successfully transplanted UCB recipients compared with MSD/MUD (P = .002). If complying with the international HCT guidelines, HCT in MPS patients results in high safety and efficacy. This allows extension of HCT to more attenuated MPS types. Because a younger age at HCT is associated with reduction of HCT-related toxicity, newborn screening may further increase safety.

A novel syndrome of congenital sideroblastic anemia, B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD).

Congenital sideroblastic anemias (CSAs) are a heterogeneous group of inherited disorders identified by pathological erythroid precursors with perinuclear mitochondrial iron deposition in bone marrow. An international collaborative group of physicians and laboratory scientists collated clinical information on cases of CSA lacking known causative mutations, identifying a clinical subgroup of CSA associated with B immunodeficiency, periodic fevers, and development delay. Twelve cases from 10 families were identified. Median age at presentation was 2 months. Anemia at diagnosis was sideroblastic, typically severe (median hemoglobin, 7.1 g/dL) and markedly microcytic (median mean corpuscular volume, 62.0 fL). Clinical course involved recurrent febrile illness and gastrointestinal disturbance, lacking an infective cause. Investigation revealed B-cell lymphopenia (CD19⁺ range, 0.016-0.22 × 109/L) and panhypogammaglobulinemia in most cases. Children displayed developmental delay alongside variable neurodegeneration, seizures, cerebellar abnormalities, sensorineural deafness, and other multisystem features. Most required regular blood transfusion, iron chelation, and intravenous immunoglobulin replacement. Median survival was 48 months, with 7 deaths caused by cardiac or multiorgan failure. One child underwent bone marrow transplantation aged 9 months, with apparent cure of the hematologic and immunologic manifestations. We describe and define a novel CSA and B-cell immunodeficiency syndrome with additional features resembling a mitochondrial cytopathy. The molecular etiology is under investigation.

Transplantation in inborn errors of metabolism: current considerations and future perspectives.

Inborn errors of metabolism (IEM) comprise an assorted group of inherited diseases, some of which are due to disordered lysosomal or peroxisomal function and some of which might be improved following haemopoietic cell transplantation (HCT). In these disorders, the onset in infancy or early childhood is typically accompanied by rapid deterioration, resulting in early death in the more severe phenotypes. Timely diagnosis and immediate referral to an IEM specialist are essential steps in optimal management. Treatment recommendations are based on the diagnosis, its phenotype, rate of progression, prior extent of disease, family values and expectations and the risks and benefits associated with available therapies, including HCT. International collaborative efforts are of utmost importance in determining outcomes of therapy for these rare diseases, and have improved those outcomes significantly over recent decades. This discussion focuses on HCT in IEM, providing an international perspective on progress, limitations, and future directions.

Impact of immune modulation with in vivo T-cell depletion and myleoablative total body irradiation conditioning on outcomes after unrelated donor transplantation for childhood acute lymphoblastic leukemia.

To determine whether in vivo T-cell depletion, which lowers GVHD, abrogates the antileukemic benefits of myeloablative total body irradiation-based conditioning and unrelated donor transplantation, in the present study, we analyzed 715 children with acute lymphoblastic leukemia. Patients were grouped for analysis according to whether conditioning included antithymocyte globulin (ATG; n = 191) or alemtuzumab (n = 132) and no in vivo T-cell depletion (n = 392). The median follow-up time was 3.5 years for the ATG group and 5 years for the alemtuzumab and T cell-replete groups. Using Cox regression analysis, we compared transplantation outcomes between groups. Compared with no T-cell depletion, grade 2-4 acute and chronic GVHD rates were significantly lower after in vivo T-cell depletion with ATG (relative risk [RR] = 0.66; P = .005 and RR = 0.55; P < .0001, respectively) or alemtuzumab (RR = 0.09; P < .003 and RR = 0.21; P < .0001, respectively). Despite lower GVHD rates after in vivo T-cell depletion, nonrelapse mortality, relapse, overall survival, and leukemia-free survival (LFS) did not differ significantly among the treatment groups. The 3-year probabilities of LFS after ATG-containing, alemtuzumab-containing, and T cell-replete transplantations were 43%, 49%, and 46%, respectively. These data suggest that in vivo T-cell depletion lowers GVHD without compromising LFS among children with acute lymphoblastic leukemia who are undergoing unrelated donor transplantation with myeloablative total body irradiation-based regimens.

Myeloid/Microglial driven autologous hematopoietic stem cell gene therapy corrects a neuronopathic lysosomal disease.

Mucopolysaccharidosis type IIIA (MPSIIIA) is a lysosomal storage disorder caused by mutations in N-sulfoglucosamine sulfohydrolase (SGSH), resulting in heparan sulfate (HS) accumulation and progressive neurodegeneration. There are no treatments. We previously demonstrated improved neuropathology in MPSIIIA mice using lentiviral vectors (LVs) overexpressing SGSH in wild-type (WT) hematopoietic stem cell (HSC) transplants (HSCTs), achieved via donor monocyte/microglial engraftment in the brain. However, neurological disease was not corrected using LVs in autologous MPSIIIA HSCTs. To improve brain expression via monocyte/microglial specificity, LVs expressing enhanced green fluorescent protein (eGFP) under ubiquitous phosphoglycerate kinase (PGK) or myeloid-specific promoters were compared in transplanted HSCs. LV-CD11b-GFP gave significantly higher monocyte/B-cell eGFP expression than LV-PGK-GFP or LV-CD18-GFP after 6 months. Subsequently, autologous MPSIIIA HSCs were transduced with either LV-PGK-coSGSH or LV-CD11b-coSGSH vectors expressing codon-optimized SGSH and transplanted into MPSIIIA mice. Eight months after HSCT, LV-PGK-coSGSH vectors produced bone marrow SGSH (576% normal activity) similar to LV-CD11b-coSGSH (473%), but LV-CD11b-coSGSH had significantly higher brain expression (11 versus 7%), demonstrating improved brain specificity. LV-CD11b-coSGSH normalized MPSIIIA behavior, brain HS, GM2 ganglioside, and neuroinflammation to WT levels, whereas LV-PGK-coSGSH partly corrected neuropathology but not behavior. We demonstrate compelling evidence of neurological disease correction using autologous myeloid driven lentiviral-HSC gene therapy in MPSIIIA mice.

Very Early-Onset IBD-Associated IL-18opathy Treated with an Anti-IL-18 Antibody.

Background/Objectives: The aetiology of inflammatory bowel disease (IBD), particularly if occurring early in childhood, is a diverse and patient-focused treatment that is required when standard therapy is ineffective. Materials and Methods: A clinical case report is presented of a child with very early-onset IBD (VEOIBD) and evidence of high serum IL-18 responding to anti-IL-18 immunotherapy. Detailed cytokine profiling was performed by ELISA and multiplex assay flow cytometry. Results: A four-year-old girl with recalcitrant VEOIBD from six weeks old due to an IL-18opathy, characterised by high blood IL-18 concentration, responded to therapy with a novel neutralising anti-IL-18 antibody (GSK1070806). After two years of hospitalisation, the child's systemic inflammation and extensive upper and lower gastrointestinal mucosal ulceration remitted with this cytokine inhibitor, allowing the discontinuation of total parenteral nutrition and the resumption of normal oral intake and daily activities. After 18 months on regular GSK1070806, the patient remains in disease remission. Conclusions: VEOIBD can be associated with evidence of an underlying IL18opathy and responds to anti-IL-18 antibody therapy. IL-18 should be measured in patients with IBD unresponsive to conventional treatments, and, if elevated, anti-IL-18 antibody therapy should be considered as a potential therapy.

Outcomes of allogeneic haematopoietic cell transplantation for myelofibrosis in children and adolescents: the retrospective study of the EBMT Paediatric Diseases WP.

This retrospective study evaluated 35 children (median age 5.2 years; range 0.4-18) with myelofibrosis (MF), including 33 with primary myelofibrosis and 2 with secondary myelofibrosis transplanted from matched sibling donor (MSD) (n = 17) or non-MSD (n = 18) between 2000 and 2022. Conditioning was usually chemotherapy-based (n = 33) and myeloablative (n = 32). Fifteen patients received bone marrow (BM), 14 haematopoietic cells (HC) from peripheral blood (PB), and 6 from cord blood (CB). Day +100 acute GvHD II-IV incidence was significantly lower after MSD-haematopoietic cell transplantation (MSD-HCT) than after non-MSD-HCT [18.8% (4.3-41.1) vs 58.8% (31-78.6); p = 0.01]. Six-year non-relapse mortality (NRM) was 18% (7.1-32.8), relapse incidence was 15.9% (5.6-30.9), progression-free survival (PFS) was 66.1% (47-79.7), GvHD-free relapse-free survival was 50% (30.6-66.7), and overall survival (OS) was 71.1% (51.4-84). Six-year PFS and OS were significantly higher after BM transplantation compared to HCT from other sources [85.1% (52.3-96.1) vs 50.8% (26.3-71), p = 0.03, and 90.9% (50.8-98.7) vs 54% (28.1-74.2), p = 0.01, respectively], whereas NRM was significantly lower [0% vs 32% (12.3-53.9); p = 0.02]. This first multicentre study on outcomes of allogeneic HCT in children with myelofibrosis proves feasibility and curative effect of transplantation in these children, suggests that bone marrow transplantation is associated with better outcomes, and indicates the need for further studies.