Prevention and Treatment of Acute Graft-versus-Host Disease in Children, Adolescents, and Young Adults

Interventional antibiotic treatment replacing antibiotic prophylaxis during allogeneic hematopoietic stem cell transplantation is safe and leads to a reduction of antibiotic administration

Patients undergoing allogeneic hematopoietic stem cell transplantation (alloHSCT) face an elevated risk of infection-related mortality, particularly during the pre-engraftment period. Although systemic antibiotic prophylaxis (SAP) is commonly employed during neutropenia, it is linked to disruptions in the intestinal microbiome, increasing the risk of graft-versus-host disease (GVHD), Clostridium difficile infection (CDI), and colonization with multi-drug resistant (MDR) bacteria. In our retrospective analysis, we evaluated the safety and efficacy of an exclusively interventional antibiotic treatment (IAT) compared to SAP in adult alloHSCT patients. In comparison to SAP, IAT resulted in a significantly reduced duration of antibiotic therapy (24 vs. 18 days, p < 0.001), although the cumulative incidence (CI) of bloodstream infections (BSI) by day + 100 post-HSCT was significantly higher in the IAT group compared to SAP (40% vs. 13%, p < 0.001). However, this did not lead to a significant increase in ICU transfers (13% vs. 6%, p = ns) or a higher CI of non-relapse mortality (NRM) at 3 years (11% vs. 10%, p = ns). With a median follow-up of 1052 days, the 3-year overall survival (OS) rates were 69% and 66% for the SAP and IAT cohorts, respectively (p = ns). The CI of acute GVHD grade II-IV (30% vs. 39%) at 100 days or chronic GVHD of any grade (50% vs. 45%) at 3 years did not differ significantly between the SAP and IAT groups. There was a tendency towards a higher CI of severe chronic GVHD in the SAP cohort (28% vs. 13%, p = 0.08). Our single center experience in conducting alloHSCT without antibiotic prophylaxis but with stringent guidelines for prompt antibiotic intervention demonstrated no disadvantages in terms of OS and NRM. IAT led to significantly reduced consumption of cefotaxime, carbapenem, and glycopeptide antibiotics. In conclusion, our findings suggest that replacing SAP with the proposed IAT procedure is both safe and feasible.

Full Validation and Application to Clinical Research of a High-Performance Liquid Chromatography Method for the Assessment of Urinary 3-Indoxyl Sulfate in Pediatric Patients with Hematopoietic Stem Cell Transplant

3-indoxyl sulfate (3-IS) results from a hepatic transformation of indole, a tryptophan degradation product produced by commensal gut bacteria. The metabolite has shown promise as a biomarker of dysbiosis and clinical outcomes following hematopoietic stem cell transplant (HSCT) in adults. Nonetheless, there is a paucity of data regarding microbiome health and outcomes in the pediatric HSCT setting. We developed and thoroughly validated an affordable high-performance liquid chromatography/fluorescence detector (HPLC-FLD) method to quantify 3-IS in urine for use in the pediatric setting. Chromatographic separation was achieved on a C18 column (250 × 4.6 mm × 5 μm) with a mobile phase consisting of pH 4.0 acetic acid-triethylamine buffer and acetonitrile (88:12, v/v), eluted isocratically at 1 mL/min. 3-IS fluorescence detection was set at excitation/emission of 280 and 375, respectively. The method was fully validated according to FDA-specified limits including selectivity, linearity (0.10 to 10.00 mg/L, r2 > 0.997), intra- and inter-day accuracy, and precision. 3-IS stability was confirmed after three freeze-thaw cycles, for short- and medium-term on a benchtop and at 4 °C and for long-term up to 60 days at -20 °C. The validated method was used to quantify 3-IS in urine samples from HSCT pediatric patients.

A Validated Risk Stratification That Incorporates MAGIC Biomarkers Predicts Long-Term Outcomes in Pediatric Patients with Acute GVHD

Acute graft versus host disease (GVHD) is a common and serious complication of allogeneic hematopoietic cell transplantation (HCT) in children but overall clinical grade at onset only modestly predicts response to treatment and survival outcomes. Two tools to assess risk at initiation of treatment were recently developed. The Minnesota risk system stratifies children for risk of nonrelapse mortality (NRM) according to the pattern of GVHD target organ severity. The Mount Sinai Acute GVHD International Consortium (MAGIC) algorithm of 2 serum biomarkers (ST2 and REG3α) predicts NRM in adult patients but has not been validated in a pediatric population. We aimed to develop and validate a system that stratifies children at the onset of GVHD for risk of 6-month NRM. We determined the MAGIC algorithm probabilities (MAPs) and Minnesota risk for a multicenter cohort of 315 pediatric patients who developed GVHD requiring treatment with systemic corticosteroids. MAPs created 3 risk groups with distinct outcomes at the start of treatment and were more accurate than Minnesota risk stratification for prediction of NRM (area under the receiver operating curve (AUC), .79 versus .62, P = .001). A novel model that combined Minnesota risk and biomarker scores created from a training cohort was more accurate than either biomarkers or clinical systems in a validation cohort (AUC .87) and stratified patients into 2 groups with highly different 6-month NRM (5% versus 38%, P < .001). In summary, we validated the MAP as a prognostic biomarker in pediatric patients with GVHD, and a novel risk stratification that combines Minnesota risk and biomarker risk performed best. Biomarker-based risk stratification can be used in clinical trials to develop more tailored approaches for children who require treatment for GVHD.

Gut Immunomodulation with Vedolizumab prior to Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients with Inflammatory Bowel Disease

Inborn errors of immunity (IEI) are often associated with inflammatory bowel disease (IBD). IEI can be corrected by allogeneic hematopoietic stem cell transplantation (HSCT); however, peritransplantation intestinal inflammation may increase the risk of gut graft-versus-host disease (GVHD). Vedolizumab inhibits the homing of lymphocytes to the intestine and may attenuate gut GVHD, yet its role in preventing GVHD in pediatric patients with IEI-associated IBD has not been studied. Here we describe a cohort of pediatric patients with IEI-associated IBD treated with vedolizumab before and during allogeneic HSCT. The study involved a retrospective chart review of pediatric patients with IEI-associated IBD treated with vedolizumab at 6 weeks, 4 weeks, and 1 week before undergoing HSCT. The conditioning regimen consisted of treosulfan, fludarabine, and cyclophosphamide with rabbit antithymocyte globulin, and GVHD prophylaxis included tacrolimus and steroids. Eleven patients (6 females) with a median age of 5 years (range, 0.4 to 14 years) with diverse IEI were included. IBD symptoms were characterized by abdominal pain, loose stools, and blood in stools. Four patients had developed a perianal fistula, and 1 patient had a rectal prolapse. One patient had both a gastrostomy tube and a jejunal tube in situ. Treatment of IBD before HSCT included steroids in 11 patients, anakinra in 2, infliximab in 4, sulfasalazine in 2, mesalazine in 2, and vedolizumab. IBD symptoms were considered controlled in the absence of abdominal pain, loose stools, or blood in stools. Graft sources for HSCT were unrelated donor cord in 5 patients (2 with a 5/8 HLA match, 2 with a 7/8 match, and 1 with a 6/8 match), peripheral blood stem cells in 5 patients (2 haploidentical, 1 with a 9/10 HLA match, and 2 with a 10/10 match), and bone marrow in 1 patient (10/10 matched sibling donor). The median number of vedolizumab infusions was 4 (range, 3 to 12) before HSCT and 1 (range, 1 to 3) after HSCT, and all were reported to be uneventful. All patients had engrafted. Acute GVHD occurred in 4 patients and was limited to grade I skin GVHD only. Chronic GVHD occurred in 1 patient and again was limited to the skin. There was no gut GVHD. Three patients experienced cytomegalovirus viremia, and 2 patients had Epstein-Barr virus viremia. At the time of this report, all patients were alive with no evidence of IBD at a median follow-up of 15 months (range, 3 to 39 months). Administration of vedolizumab pre- and post-HSCT in pediatric patients with IEI-associated IBD is well tolerated and associated with a low rate of gut GVHD. These findings provide a platform for the prospective study and use of vedolizumab for GVHD prophylaxis in pediatric patients with known intestinal inflammation as a pre-HSCT comorbidity.

Risk factors for acute kidney injury in pediatric patients after hematopoietic stem cell transplantation: a systematic review and meta-analysis

BACKGROUND

Risk factors for acute kidney injury (AKI) in pediatric patients after hematopoietic stem cell transplantation (HSCT) remain controversial.

OBJECTIVES

This study aimed to identify risk factors for AKI following HSCT in the pediatric population.

DATA SOURCES

PubMed, Embase, Web of Science, Cochrane Library, and Scopus databases were searched from inception to February 8, 2023.

STUDY ELIGIBILITY CRITERIA

Studies meeting the following criteria were included: (1) The study was a case-control, cohort study, or cross-sectional design, (2) the study was performed among pediatric and young patients aged 21 years or younger undergoing HSCT, (3) the study measured at least one related factor for AKI after pediatric HSCT, (4) the study included a sample of at least ten patients, and (5) original articles published in English in peer-reviewed scientific journals.

PARTICIPANTS AND INTERVENTIONS

Children who were undergoing pediatric HSCT.

STUDY APPRAISAL AND SYNTHESIS METHODS

We assessed the quality of the included studies and analyzed them with a random-effect model.

RESULTS

Fifteen studies with a total of 2,093 patients were included. All were cohort studies of high quality. The overall pooled incidence of AKI was 47.4% (95%CI 0.35, 0.60). We found significant associations between post-transplant AKI in pediatric patients and unrelated donor [odds ratio (OR) = 1.74, 95% confidence interval (CI) 1.09-2.79], cord blood stem cell transplantation (OR = 3.14, 95%CI 2.14-4.60), and veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS) (OR = 6.02, 95%CI 1.40-25.88). Other controversial factors such as myeloablative conditioning (MAC), acute graft vs. host disease (aGVHD), and the use of calcineurin inhibitors (CNI) were not found to be related to AKI after pediatric HSCT.

LIMITATIONS

Results were limited mainly by heterogeneity in the characteristics of patients and transplantation.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Posttransplant AKI in children is a common complication. Unrelated donors, cord blood stem cell transplantation, and VOD/SOS might be risk factors for AKI after pediatric HSCT. Further large-scale studies are still needed to draw firm conclusions.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42022382361 A higher resolution version of the Graphical abstract is available as Supplementary information.

Improvement of survival after hematopoietic stem cell transplantation and trends at a pediatric transplantation center; a three-decade journey

BACKGROUND

Advances in stem cell transplantation have resulted in improved outcomes.

METHODS

This is a retrospective study aimed to analyze changes in patient profile, transplantation, graft characteristics, and outcome among 241 pediatric patients who received stem cell transplantation in a single center between 1993 and 2019.

RESULTS

In the 2010-2019, compared with the 1993-2009 period, a significantly higher 5-year overall survival (60% vs. 44%, p = .022) and an event-free survival (53% vs. 34%, p = .025) were observed. Cumulative incidence of deaths due to relapse or progression between the 1993-2009 and 2010-2019 periods were 33% and 26% respectively (p = .66). Cumulative incidence of non-relapse mortality was significantly higher during the 1993-2009 period compared with the 2010-2019 period for malignant diseases (57.7% vs. 28.3%, p = .007). The overall survival from acute graft-versus-host disease between 1993 and 2009 was 11% versus 46% between 2010 and 2019 (p = .0001). The overall survival from infection in both eras did not show any difference (p = .41).

CONCLUSIONS

Development in transplantation technology has led to a decrease in non-relapse mortality and better control of graft-versus-host disease. However, relapse and infection remained as major causes of death. Studies evaluating institutional trends in patients undergoing HSCT and analyzing their mortality profile, can improve the management of patients, leading to a reduction in transplant-related problems.

Post-transplant сyclophosphamide after matched donor hematopoietic stem cell transplantation in children with acute leukemia

INTRODUCTION

The data on post-transplant cyclophosphamide (PTCy) in pediatric acute leukemia after matched allo-HSCT are limited to case series. The present study aimed to assess the results of PTCy-based GVHD prophylaxis in a large cohort of children with acute leukemia after matched allo-HSCT.

METHODS

A retrospective analysis of 190 pediatric patients with acute leukemia who had a first allograft between 2008 and 2020 from a matched sibling donor (MSD) or matched unrelated donor (MUD) was carried out. In the MSD setting, GVHD prophylaxis consisted of PTCy alone (n = 28) for the study group, and calcineurin inhibitor (CNI) ± antimetabolite (n = 30) for the control group. In MUD setting, most patients in the study group received GVHD prophylaxis with PTCy+CNI+mycophenolate mofetil (n = 42, 66.7%) or PTCy+CNI+sirolimus (n = 12, 19%). All patients (n = 69) in the control group received ATG+CNI+antimetabolite.

RESULTS

After MUD allo-HSCT, the incidences of acute GVHD grade III-IV and moderate/severe chronic GVHD were significantly lower in the PTCy group compared to control (6.6% vs. 35.0% and 12.7% vs. 47.1%, respectively, p < .0001). Five-year GVHD-free, relapse-free survival (GRFS) after MUD allo-HSCT was higher in the PTCy group compared to control (35.1% vs. 7.3%, p < .0001). At the same time, there was no significant difference between both groups after MSD allo-HSCT.

CONCLUSIONS

In pediatric acute leukemia, PTCy-based GVHD prophylaxis for MUD allo-HSCT is a feasible and effective option that results in a low incidence of GVHD. Compared to the ATG-based approach, PTCy provides better control of GVHD in children. In pediatric allo-HSCT from MSD, PTCy demonstrates comparable effectiveness to conventional GVHD prophylaxis.

Stem cell transplantation for ALL: you've always got a donor, why not always use it?

Hematopoietic stem cell transplantation (HSCT) represents a consolidated therapeutic strategy for high-risk pediatric acute lymphoblastic leukemia (ALL), offering the potential for curative treatment. This manuscript delves into the debate around the more universal application of HSCT for pediatric ALL in the modern era, considering the ubiquitous availability of suitable donors. In fact, despite significant advancements in chemotherapy, targeted therapy, and immunotherapy, a subset of pediatric patients with ALL with high-risk features or relapse continue to encounter poor prognostic outcomes. For this subgroup of patients, HSCT often remains the only potentially curative measure, leveraging the graft-versus- leukemia effect for long-term disease control. Nevertheless, the procedure's complexity and associated risks have traditionally curtailed its widespread use. However, the scenario is shifting with improvements in HLA matching, availability of alternative donor sources, less toxic conditioning regimens, and improved supportive care protocols. Concurrently, emerging therapies like CD19+ CAR T cells present new considerations for definitive therapy selection in relapsed/ refractory ALL. This article reviews critical current evidence and debates the potential of HSCT as a more universal treatment for ALL, reevaluating traditional treatment stratification in light of the constant availability of stem cell donors.

Generation of Human Regulatory Dendritic Cells from Cryopreserved Healthy Donor Cells and Hematopoietic Stem Cell Transplant Recipients

Acute graft versus host disease (GVHD) remains a significant complication following hematopoietic stem cell transplant (HSCT), despite improved human leukocyte antigen (HLA) matching and advances in prophylactic treatment regimens. Previous studies have shown promising results for future regulatory dendritic cell (DCreg) therapies in the amelioration of GVHD. This study evaluates the effects of cryopreservation on the generation of DCreg, the generation of young and older DCreg in serum-free media, and the feasibility of generating DCreg from young and older HSCT patient monocytes. DCregs were generated in X-vivo 15 serum-free media from donor or patient monocytes. This study includes the use of monocytes from young and older healthy, donor, and HSCT patients with varying hematological diseases. Phenotypic differences in cell populations were assessed via flow cytometry while pro-inflammatory and anti-inflammatory cytokine production was evaluated in culture medium. The number of DCreg generated from cryopreserved monocytes of healthy donors was not significantly different from freshly isolated monocytes. DCreg generated from cryopreserved monocytes had comparable levels of co-stimulatory molecule expression, inhibitory molecule expression, and cytokine production as freshly isolated monocytes. Young and older healthy donor monocytes generated similar numbers of DCreg with similar cytokine production and phenotype. Although monocytes from older HSCT patients generated significantly fewer DCreg, DCreg from young and older HSCT patients had comparable phenotypes and cytokine production. Monocytes from young and older myelodysplastic syndrome (MDS) patients generated reduced numbers of DCreg compared to non-MDS-derived DCreg. We demonstrate that the cryopreservation of monocytes from HSCT patients of varying hematological diseases allows for the cost-effective generation of DCreg on an as-needed basis. Although the generation of DCreg from MDS patients requires further assessment, these data support the possibility of in vitro-generated DCreg as a therapy to reduce GVHD-associated morbidity and mortality in young and older HSCT recipients.

Treatment of steroid-refractory graft versus host disease in children

Systemic steroids are still the first-line approach in acute graft-versus-host disease (aGvHD), and the backbone of chronic GvHD management. Refractoriness to steroid represent a major cause of morbidity and non-relapse mortality after hematopoietic stem cell transplantation (HSCT). In both backgrounds, several second-line immunosuppressive agents have been tested with variable results in terms of efficacy and toxicity. Solid evidence regarding these approaches is still lacking in the pediatric setting where results are mainly derived from adult experiences. Furthermore, the number of treated patients is limited and the incidence of acute and chronic GvHD is lower, resulting in a very heterogeneous approach to this complication by pediatric hematologists. Some conventional therapies and anti-cytokine monoclonal antibodies used in the adult setting have been evaluated in children. In recent years, the increasing understanding of the biological mechanisms underpinning the pathogenesis of GvHD justified the efforts toward the adoption of targeted therapies and non-pharmacologic approaches, with higher response rates and lower immunosuppressive effects. Moreover, many questions regarding the precise timing and setting in which to integrate these new approaches remain unanswered. This Review aims to critically explore the current evidence regarding novel approaches to treat SR-GvHD in pediatric HSCT recipients.

Precision Delivery of Steroids as a Rescue Therapy for Gastrointestinal Graft-versus-Host Disease in Pediatric Stem Cell Transplant Recipients

Graft versus host disease (GVHD) is one of the most serious complications following stem cell transplant in children and is a major cause of morbidity and mortality. Corticosteroids remain the mainstay of treatment, and although a majority of children respond to systemic steroids, those refractory to or dependent upon corticosteroids suffer from complications secondary to long-term steroid administration. This problem has prompted consideration of steroid-sparing treatment strategies, although the time to clinical remission can be variable. Intraarterial corticosteroid delivery has been used in adults as a rescue therapy in steroid-resistant patients, but its use in children has been limited. We investigated the feasibility of intraarterial steroid administration into the bowel and/or liver in a cohort of six pediatric patients with acute GVHD. All patients successfully underwent treatment with no serious adverse effects. Five of five (100%) patients with gastrointestinal bleeding due to GVHD had rapid symptom improvement by 48 h, which was durable up to three weeks. Three of four (75%) patients with hepatic GVHD had improved cholestasis following intraarterial steroid administration. Our experience with this small cohort preliminarily demonstrated the feasibility and safety of intraarterial steroid administration in children with acute GVHD. This approach warrants consideration as a rescue therapy in steroid-refractory cases and as a "bridge" therapy for children with severe acute GVHD who are transitioning to steroid-sparing regimens.

What is Next in Pediatric B-cell Precursor Acute Lymphoblastic Leukemia

Cure rates now exceed 90% in many contemporary trials for children with B-cell acute lymphoblastic leukemia (ALL). However, treatment remains suboptimal and therapy is toxic for all patients. New treatment options potentially offer the chance to reduce both treatment resistance and toxicity. Here, we review recent advances in ALL diagnostics, chemotherapy, and immunotherapy. In addition to describing recently published results, we also attempt to project the impact of these new developments into the future to imagine what B-ALL therapy may look like in the next few years.

Harnessing and honing mesenchymal stem/stromal cells for the amelioration of graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is a deterministic curative procedure for various hematologic disorders and congenital immunodeficiency. Despite its increased use, the mortality rate for patients undergoing this procedure remains high, mainly due to the perceived risk of exacerbating graft-versus-host disease (GVHD). However, even with immunosuppressive agents, some patients still develop GVHD. Advanced mesenchymal stem/stromal cell (MSC) strategies have been proposed to achieve better therapeutic outcomes, given their immunosuppressive potential. However, the efficacy and trial designs have varied among the studies, and some research findings appear contradictory due to the challenges in characterizing the in vivo effects of MSCs. This review aims to provide real insights into this clinical entity, emphasizing diagnostic, and therapeutic considerations and generating pathophysiology hypotheses to identify research avenues. The indications and timing for the clinical application of MSCs are still subject to debate.

Complications and Utility of Gastrointestinal Endoscopy Post Hematopoietic Stem Cell Transplantation: An 11 Year Experience

OBJECTIVES

Diagnostic gastrointestinal (GI) endoscopy is used to differentiate GI graft versus host disease (GI-GvHD), which requires escalation of immunosuppressive treatment (IST), from other conditions such as viral infection, which may require reduction of IST. The aim of this study was to establish the clinical utility of GI endoscopy post hematopoietic stem cell transplant (HSCT) and the complication rate of these procedures.

METHODS

This was a single-center observational retrospective cohort study. Hospital pediatric endoscopy and HSCT databases identified patients between January 2010 and December 2020. GI-GvHD was diagnosed if there were positive histological findings and clinical context. Data collected included demographics, timing of endoscopy post-HSCT, clinical utility, and complications of endoscopy. The endoscopy was deemed to be "clinically useful" if it resulted in a change of clinical management or helped to narrow down the differential diagnosis for the clinical team.

RESULTS

Three hundred thirty-nine HSCT occurred in 320 children during the study period. Sixty-six of 339 (19%) HSCT needed an "endoscopy episode." One hundred nineteen endoscopies were performed (53 concurrent upper and lower GI endoscopies, 11 upper GI endoscopies, and 2 lower GI endoscopies). Four of 119 (3%) endoscopies had complications: septic shock (1), duodenal hematoma (1), GI bleeding (1), and colonic perforation (1). Four patients had incomplete records to assess utility of endoscopy. Fifty-seven of 62 (92%) endoscopy episodes were "clinically useful," and 41 of 62 (66%) had a change in IST.

CONCLUSIONS

The clinical utility of endoscopy is high and in the majority of cases is associated with a change in patient management. Children post-HSCT are at high risk of complications from endoscopy; this should be made clear in the process of obtaining consent for procedures.

Vedolizumab for pediatric patients with gastrointestinal acute graft-versus-host-disease

Vedolizumab, an anti-α4β7 integrin monoclonal antibody, impairs homing of T-cells to the gastrointestinal (GI) endothelium and acts as a gut-selective anti-inflammatory agent. Recent reports of the efficacy of vedolizumab in treating lower GI acute graft-versus-host disease (aGVHD) are promising, but experience in children is scarce. We present a cohort of 13 pediatric patients who were treated with vedolizumab for GI aGVHD. Ten of the patients were treated for steroid-refractory disease, out of which, six suffered from severe (stage 3 or 4) GI disease before the first dose of vedolizumab. In the other three patients, vedolizumab was introduced early in the disease course. Median time between GI GVHD onset to vedolizumab treatment was 23 days (range 7-59 days), with a median of 3 doses (range 1-5) per patient. GI GVHD staging was evaluated at various time points after the first vedolizumab dose, showing improvement in nine of the 13 patients. After a median follow-up time of 13 months (range 6-34 months), eight patients completely recovered, two had ongoing chronic colitis, and three patients died. During the vedolizumab treatment period, 38 infectious episodes were noted, most of them GI related. The unique activity profile of vedolizumab makes it an appealing treatment option for lower GI aGVHD, but caution for concurrent infections is warranted.

Extracorporeal photopheresis versus standard treatment for acute graft-versus-host disease after haematopoietic stem cell transplantation in children and adolescents

BACKGROUND

Acute graft-versus-host disease (aGvHD) is a major cause of morbidity and mortality after haematopoietic stem cell transplantation (HSCT), occurring in 8% to 85% of paediatric recipients. Currently, the therapeutic mainstay for aGvHD is treatment with corticosteroids. However, there is no established standard treatment for steroid-refractory aGvHD. Extracorporeal photopheresis (ECP) is a type of immunomodulatory method amongst different therapeutic options that involves ex vivo collection of peripheral mononuclear cells, exposure to the photoactive agent 8-methoxypsoralen and ultraviolet-A radiation, and reinfusion of these treated blood cells to the patient. The mechanisms of action of ECP are not completely understood. This is the second update of a Cochrane Review first published in 2014 and updated in 2015.

OBJECTIVES

To evaluate the effectiveness and safety of ECP for the management of aGvHD in children and adolescents after HSCT.

SEARCH METHODS

We searched the Cochrane Register of Controlled Trials (CENTRAL), MEDLINE (PubMed) and Embase (Ovid) databases from their inception to 25 January 2021. We searched the reference lists of potentially relevant studies without any language restrictions. We searched five conference proceedings and nine clinical trial registries on 9 November 2020 and 12 November 2020, respectively.

SELECTION CRITERIA

We sought to include randomised controlled trials (RCTs) comparing ECP with or without standard treatment versus standard treatment alone in children and adolescents with aGvHD after HSCT.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection. We resolved disagreement in the selection of trials by consultation with a third review author.

MAIN RESULTS

We identified no additional studies in the 2021 review update, so there are still no studies that meet the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy of ECP in the treatment of aGvHD in children and adolescents after HSCT is unknown, and its use should be restricted to within the context of RCTs. Such studies should address a comparison of ECP alone or in combination with standard treatment versus standard treatment alone. The 2021 review update brought about no additions to these conclusions.

Post-Transplant Cyclophosphamide after Matched Sibling and Unrelated Donor Hematopoietic Stem Cell Transplantation in Pediatric Patients with Acute Myeloid Leukemia

Non-relapse mortality due to GVHD and infections represents a major source of morbidity and mortality in pediatric HSCT recipients. Post-transplant cyclophosphamide (PTCy) has emerged as an effective and safe GVHD prophylaxis strategy, with improved GVHD and relapse-free survival in matched (related and unrelated) and mismatched haploidentical HSCT adult recipients. However, there are no published data in pediatric patients with acute myeloid leukemia who received matched-donor HSCT with PTCy. We demonstrate, in this case series, that the use of PTCy in this population is potentially safe, effective in preventing acute GVHD, does not impair engraftment, is associated with reduced non-relapse mortality, and does not hinder immune reconstitution post HSCT.

Immune Suppression in Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for high-risk hematologic disorders. There are multiple immune-mediated complications following allo-HSCT that are prevented and/or treated by immunosuppressive agents. Principal among these immune-mediated complications is acute graft-versus-host disease (aGVHD), which occurs when the new donor immune system targets host tissue antigens. The immunobiology of aGVHD is complex and involves all aspects of the immune system. Due to the risk of aGVHD, immunosuppressive aGVHD prophylaxis is required for nearly all allogeneic HSCT recipients. Despite prophylaxis, aGVHD remains a major cause of nonrelapse mortality. Here, we discuss the clinical features of aGVHD, the immunobiology of aGVHD, the immunosuppressive therapies used to prevent and treat aGVHD, how to mitigate the side effects of these immunosuppressive therapies, and what additional immune-mediated post-allo-HSCT complications are also treated with immunosuppression.

Cytokine Release Syndrome in the Immunotherapy of Hematological Malignancies: The Biology behind and Possible Clinical Consequences

Cytokine release syndrome (CRS) is an acute systemic inflammatory syndrome characterized by fever and multiple organ dysfunction associated with (i) chimeric antigen receptor (CAR)-T cell therapy, (ii) therapeutic antibodies, and (iii) haploidentical allogeneic stem cell transplantation (haplo-allo-HSCT). Severe CRS can be life-threatening in some cases and requires prompt management of those toxicities and is still a great challenge for physicians. The pathophysiology of CRS is still not fully understood, which also applies to the identifications of predictive biomarkers that can forecast these features in advance. However, a broad range of cytokines are involved in the dynamics of CRS. Treatment approaches include both broad spectrum of immunosuppressant, such as corticosteroids, as well as more specific inhibition of cytokine release. In the present manuscript we will try to review an update regarding pathophysiology, etiology, diagnostics, and therapeutic options for this serious complication.

Beyond steroids: A systematic review and proposed solutions to managing acute graft-versus-host disease in adolescents and young adults

The outcomes of allogeneic hematopoietic cell transplantation (HCT) in adolescents and young adults (AYAs) with hematologic malignancies have been shown to be poorer when compared to results in children, due to a combination of higher relapse rates and greater treatment-related mortality (TRM). Although differences in relapse risk have been studied extensively, toxicity has been examined and reported less often. In this systematic review, we summarize recently published studies that have examined the differences in rates of TRM and acute graft-versus-host disease (GVHD) in AYAs and children with hematologic malignancies, and attempt to explain why these disparities exist and how they impact outcomes. In addition, we present best practices for management of steroid-refractory GVHD that are likely to improve survival in this patient population. Further, we propose the development of personalized, risk-based approaches for the prevention and treatment of GVHD that incorporate novel platforms and interventions. We believe this individualized approach is likely to reduce toxicity and greatly improve outcomes for this vulnerable population.

Invasive Fungal Diseases in Children with Hematological Malignancies Treated with Therapies That Target Cell Surface Antigens: Monoclonal Antibodies, Immune Checkpoint Inhibitors and CAR T-Cell Therapies

Since 1985 when the first agent targeting antigens on the surface of lymphocytes was approved (muromonab-CD3), a multitude of such therapies have been used in children with hematologic malignancies. A detailed literature review until January 2021 was conducted regarding pediatric patient populations treated with agents that target CD2 (alefacept), CD3 (bispecific T-cell engager [BiTE] blinatumomab), CD19 (denintuzumab mafodotin, B43, BiTEs blinatumomab and DT2219ARL, the immunotoxin combotox, and chimeric antigen receptor [CAR] T-cell therapies tisagenlecleucel and axicabtagene ciloleucel), CD20 (rituximab and biosimilars, 90Y-ibritumomab tiuxetan, ofatumumab, and obinutuzumab), CD22 (epratuzumab, inotuzumab ozogamicin, moxetumomab pasudotox, BiTE DT2219ARL, and the immunotoxin combotox), CD25 (basiliximab and inolimomab), CD30 (brentuximab vedotin and iratumumab), CD33 (gemtuzumab ozogamicin), CD38 (daratumumab and isatuximab), CD52 (alemtuzumab), CD66b (90Y-labelled BW 250/183), CD248 (ontuxizumab) and immune checkpoint inhibitors against CTLA-4 (CD152; abatacept, ipilimumab and tremelimumab) or with PD-1/PD-L1 blockade (CD279/CD274; atezolizumab, avelumab, camrelizumab, durvalumab, nivolumab and pembrolizumab). The aim of this narrative review is to describe treatment-related invasive fungal diseases (IFDs) of each category of agents. IFDs are very common in patients under blinatumomab, inotuzumab ozogamicin, basiliximab, gemtuzumab ozogamicin, alemtuzumab, and tisagenlecleucel and uncommon in patients treated with moxetumomab pasudotox, brentuximab vedotin, abatacept, ipilimumab, pembrolizumab and avelumab. Although this new era of precision medicine shows promising outcomes of targeted therapies in children with leukemia or lymphoma, the results of this review stress the necessity for ongoing surveillance and suggest the need for antifungal prophylaxis in cases where IFDs are very common complications.

The role of the thymus in allogeneic bone marrow transplantation and the recovery of the peripheral T-cell compartment

As the thymus represents the primary site of T-cell development, optimal thymic function is of paramount importance for the successful reconstitution of the adaptive immunity after allogeneic hematopoietic stem cell transplantation. Thymus involutes as part of the aging process and several factors, including previous chemotherapy treatments, conditioning regimen used in preparation to the allograft, occurrence of graft-versus-host disease, and steroid therapy that impair the integrity of the thymus, thus affecting its role in supporting T-cell neogenesis. Although the pathways governing its regeneration are still poorly understood, the thymus has a remarkable capacity to recover its function after damage. Measurement of both recent thymic emigrants and T-cell receptor excision circles is valuable tools to assess thymic output and gain insights on its function. In this review, we will extensively discuss available data on factors regulating thymic function after allogeneic hematopoietic stem cell transplantation, as well as the strategies and therapeutic approaches under investigation to promote thymic reconstitution and accelerate immune recovery in transplanted patients, including the use of cytokines, sex-steroid ablation, precursor T-cells, and thymus bioengineering. Although none of them is routinely used in the clinic, these approaches have the potential to enhance thymic function and immune recovery, not only in patients given an allograft but also in other conditions characterized by immune deficiencies related to a defective function of the thymus.

Current Prophylaxis and Treatment Approaches for Acute Graft-Versus-Host Disease in Haematopoietic Stem Cell Transplantation for Children With Acute Lymphoblastic Leukaemia

Acute graft-versus-host disease (aGvHD) continues to be a leading cause of morbidity and mortality following allogeneic haematopoietic stem cell transplantation (HSCT). However, higher event-free survival (EFS) was observed in patients with acute lymphoblastic leukaemia (ALL) and grade II aGvHD vs. patients with no or grade I GvHD in the randomised, controlled, open-label, international, multicentre Phase III For Omitting Radiation Under Majority age (FORUM) trial. This finding suggests that moderate-severity aGvHD is associated with a graft-versus-leukaemia effect which protects against leukaemia recurrence. In order to optimise the benefits of HSCT for leukaemia patients, reduction of non-relapse mortality-which is predominantly caused by severe GvHD-is of utmost importance. Herein, we review contemporary prophylaxis and treatment options for aGvHD in children with ALL and the key challenges of aGvHD management, focusing on maintaining the graft-versus-leukaemia effect without increasing the severity of GvHD.

Broad-Spectrum Antibiotics and Risk of Graft-versus-Host Disease in Pediatric Patients Undergoing Transplantation for Acute Leukemia: Association of Carbapenem Use with the Risk of Acute Graft-versus-Host Disease

Variation in the gastrointestinal (GI) microbiota after hematopoietic cell transplantation (HCT) has been associated with acute graft-versus-host disease (aGVHD). Because antibiotics induce dysbiosis, we examined the association of broad-spectrum antibiotics with subsequent aGVHD risk in pediatric patients undergoing HCT for acute leukemia. We performed a retrospective analysis in a dataset merged from 2 sources: (1) the Center for International Blood and Marrow Transplant Research, an observational transplantation registry, and (2) the Pediatric Health Information Services, an administrative database from freestanding children's hospitals. We captured exposure to 3 classes of antibiotics used for empiric treatment of febrile neutropenia: (1) broad-spectrum cephalosporins, (2) antipseudomonal penicillins, and (3) carbapenems. The primary outcome was grade II-IV aGVHD; secondary outcomes were grade III-IV aGVHD and lower GI GVHD. The adjusted logistic regression model (full cohort) and time-to-event analysis (subcohort) included transplantation characteristics, GVHD risk factors, and adjunctive antibiotic exposures as covariates. The full cohort included 2550 patients at 36 centers; the subcohort included 1174 patients. In adjusted models, carbapenems were associated with an increased risk of grade II-IV aGVHD in the full cohort (adjusted odds ratio [aOR], 1.24; 95% confidence interval [CI], 1.02 to 1.51) and subcohort (sub hazard ratio [HR], 1.31; 95% CI, 0.99 to 1.72), as well as with an increased risk of grade III-IV aGVHD (subHR, 1.77; 95% CI, 1.25 to 2.52). Early carbapenem exposure (before day 0) especially impacted aGVHD risk. For antipseudomonal penicillins, the associations with aGVHD were in the direction of increased risk but were not statistically significant. There was no identified association between broad-spectrum cephalosporins and aGVHD. Carbapenems, more than other broad-spectrum antibiotics, should be used judiciously in pediatric HCT recipients to minimize aGVHD risk. Further research is needed to clarify the mechanism underlying this association.

The gut microbiome in pediatric patients undergoing allogeneic hematopoietic stem cell transplantation

The gut microbiome (GM) has been associated with different clinical outcomes in the context of allogeneic hematopoietic stem cell transplantation (HSCT). Large multicenter cohort studies in adults have found significant correlations with overall survival, relapse, and incidence of complications. Moreover, GM is already a promising target for therapeutic interventions. However, few data are available in children, a population presenting unique features and challenges. During childhood, the GM evolves rapidly with large structural fluctuations, alongside with the maturation of the immune system. Furthermore, the HSCT procedure presents significant differences in children. These considerations underline the importance of a specific focus on the pediatric setting, and the role of GM and its age-dependent trajectory in influencing the immunity reconstitution and clinical outcomes. This review provides a comprehensive overview of the available evidence in the field of GM and pediatric HSCT, highlighting age-specific issues and discussing GM-based therapeutic approaches.