Matched unrelated donor transplantation versus haploidentical transplantation with post-transplant cyclophosphamide in children with acute myeloid leukemia: a PDWP-EBMT study.

In children with acute myeloid leukemia (AML) who lack a human leukocyte antigen (HLA) identical sibling, the donor can be replaced with an HLA-matched unrelated donor (MUD) or a haploidentical donor (haplo). We compared outcomes of patients <18 years with AML in first and second complete remission (CR1 and CR2) undergoing a hematopoietic stem cell transplantation (HCT) either with a MUD with anti-thymocyte globulin (ATG) (N=420) or a haplo HCT with post-transplant cyclophosphamide (PT-CY) (N=96) after a myeloablative conditioning regimen (MAC) between 2011 and 2021, reported to the European Society for Blood and Marrow Transplantation. A matched pair analysis was performed to adjust for differences among groups. The final analysis was performed on 253 MUD and 95 haplo-HCT. In the matched cohort, median age at HCT was 11.2 and 10 years and median year of HCT was 2017 and 2018, in MUD and haplo-HCT recipients, respectively. The risk of grade III-IV acute graft-versus-host disease (aGVHD) was significantly higher in the haplo group (hazard ratio [HR]=2.33, 95% confidence interval [CI]: 1.18-4.58; P=0.01). No significant differences were found in 2 years overall survival (OS; 78.4% vs. 71.5%; HR=1.39, 95% CI: 0.84-2.31; P=0.19), leukemia-free survival (LFS; 72.7% vs. 69.5%; HR=1.22, 95% CI: 0.76-1.95; P=0.41), CI of relapse (RI; 19.3% vs. 19.5%; HR=1.14, 95% CI: 0.62-2.08; P=0.68) non-relapse-mortality (NRM; 8% vs. 11%; HR=1.39, 95% CI: 0.66-2.93; P=0.39) and graft-versus-host free relapse-free survival (GRFS; 60.7% vs. 54.5%, HR=1.38, 95% CI: 0.95-2.02; P=0.09) after MUD and haplo-HCT respectively. Our study suggests that haplo-HCT with PT-CY is a suitable option to transplant children with AML lacking a matched related donor.

Management of children and adolescents with chronic myeloid leukemia in blast phase: International pediatric CML expert panel recommendations.

Treatment of chronic myeloid leukemia has improved significantly with the introduction of tyrosine kinase inhibitors (TKIs), and treatment guidelines based on numerous clinical trials are available for chronic phase disease. However for CML in the blast phase (CML-BP), prognosis remains poor and treatment options are much more limited. The spectrum of treatment strategies for children and adolescents with CML-BP has largely evolved empirically and includes treatment principles derived from adult CML-BP and pediatric acute leukemia. Given this heterogeneity of treatment approaches, we formed an international panel of pediatric CML experts to develop recommendations for consistent therapy in children and adolescents with this high-risk disease based on the current literature and national standards. Recommendations include detailed information on initial diagnosis and treatment monitoring, differentiation from Philadelphia-positive acute leukemia, subtype-specific selection of induction therapy, and combination with tyrosine kinase inhibitors. Given that allogeneic hematopoietic stem cell transplantation currently remains the primary curative intervention for CML-BP, we also provide recommendations for the timing of transplantation, donor and graft selection, selection of a conditioning regimen and prophylaxis for graft-versus-host disease, post-transplant TKI therapy, and management of molecular relapse. Management according to the treatment recommendations presented here is intended to provide the basis for the design of future prospective clinical trials to improve outcomes for this challenging disease.

CD4+ T-cell reconstitution predicts survival outcomes after acute graft-versus-host-disease: a dual-center validation.

Acute graft-versus-host-Disease (aGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). We previously showed that early CD4+ T-cell immune reconstitution (IR; CD4+ IR) predicts survival after HCT. Here, we studied the relation between CD4+ IR and survival in patients developing aGVHD. Pediatric patients undergoing first allogeneic HCT at University Medical Center Utrecht (UMC)/Princess Máxima Center (PMC) or Memorial Sloan Kettering Cancer Center (MSK) were included. Primary outcomes were nonrelapse mortality (NRM) and overall survival (OS), stratified for aGVHD and CD4+ IR, defined as ≥50 CD4+ T cells per µL within 100 days after HCT or before aGVHD onset. Multivariate and time-to-event Cox proportional hazards models were applied, and 591 patients (UMC/PMC, n = 276; MSK, n = 315) were included. NRM in patients with grade 3 to 4 aGVHD with or without CD4+ IR within 100 days after HCT was 30% vs 80% (P = .02) at UMC/PMC and 5% vs 67% (P = .02) at MSK. This was associated with lower OS without CD4+ IR (UMC/PMC, 61% vs 20%; P = .04; MSK, 75% vs 33%; P = .12). Inadequate CD4+ IR before aGVHD onset was associated with significantly higher NRM (74% vs 12%; P < .001) and inferior OS (24% vs 78%; P < .001). In this retrospective analysis, we demonstrate that early CD4+ IR, a simple and robust marker predictive of outcomes after HCT, is associated with survival after moderate to severe aGVHD. This association must be confirmed prospectively but suggests strategies to improve T-cell recovery after HCT may influence survival in patients developing aGVHD.

PICU Admission Rates in Pediatric Cancer and Hematopoietic Stem Cell Transplant Patients Receiving High-flow Nasal Cannula Oxygen Therapy on the General Ward.

The use of high-flow nasal cannula (HFNC) oxygen therapy is growing as an alternative to standard oxygen. However, its use in patients treated for malignancies, including hematopoietic stem cell transplantation (HSCT) patients, is controversial. In this retrospective cohort study, we assessed outcomes of pediatric cancer and HSCT patients (including nonmalignant indications) with acute hypoxemic respiratory failure treated with HFNC on the ward. Among 39 patients included in the study, 53 episodes of HFNC treatment were analyzed. Of these episodes, 18 (34%) failed and patients required subsequently pediatric intensive care unit (PICU) admission. A significant median higher C reactive protein (175 [range, 72 to 308] vs. 80 [13.5 to 187.8] mg/dL; P=0.006) and higher Bedside Pediatric Early Warning Score (PEWS) 1 to 4 hours after initiation of HFNC (10.1±0.8 vs. 7.1±0.4; P=0.001) was found in the failure group compared with the nonfailure group. Among the 18 patients admitted to PICU, 14 (78%) needed intubation. Five (28%) patients died during their PICU admission. In summary, one third of the pediatric cancer and HSCT patients receiving HFNC on the ward eventually required PICU admission of which 78% were intubated. C reactive protein and BedsidePEWS 1 to 4 hours after initiation of HFNC were significantly associated with the need for PICU admission. However, no firm conclusion can be drawn whether HFNC treatment should actually be initiated in the ward in this vulnerable patient population. Larger, prospective studies are needed to evaluate the most appropriate treatment and setting (PICU or general ward) for these patients.

Rapid and reproducible characterization of sickling during automated deoxygenation in sickle cell disease patients.

In sickle cell disease (SCD), sickle hemoglobin (HbS) polymerizes upon deoxygenation, resulting in sickling of red blood cells (RBCs). These sickled RBCs have strongly reduced deformability, leading to vaso-occlusive crises and chronic hemolytic anemia. To date, there are no reliable laboratory parameters or assays capable of predicting disease severity or monitoring treatment effects. We here report on the oxygenscan, a newly developed method to measure RBC deformability (expressed as Elongation Index - EI) as a function of pO2 . Upon a standardized, 22 minute, automated cycle of deoxygenation (pO2 median 16 mmHg ± 0.17) and reoxygenation, a number of clinically relevant parameters are produced in a highly reproducible manner (coefficients of variation <5%). In particular, physiological modulators of oxygen affinity, such as, pH and 2,3-diphosphoglycerate showed a significant correlation (respectively R = -0.993 and R = 0.980) with Point of Sickling (PoS5% ), which is defined as the pO2 where a 5% decrease in EI is observed during deoxygenation. Furthermore, in vitro treatment with antisickling agents, including GBT440, which alter the oxygen affinity of hemoglobin, caused a reproducible left-shift of the PoS, indicating improved deformability at lower oxygen tensions. When RBCs from 21 SCD patients were analyzed, we observed a significantly higher PoS in untreated homozygous SCD patients compared to treated patients and other genotypes. We conclude that the oxygenscan is a state-of-the-art technique that allows for rapid analysis of sickling behavior in SCD patients. The method is promising for personalized treatment, development of new treatment strategies and could have potential in prediction of complications.

The fluid membrane determines mechanics of erythrocyte extracellular vesicles and is softened in hereditary spherocytosis.

Extracellular vesicles (EVs) are widely studied regarding their role in cell-to-cell communication and disease, as well as for applications as biomarkers or drug delivery vehicles. EVs contain membrane and intraluminal proteins, affecting their structure and thereby likely their functioning. Here, we use atomic force microscopy for mechanical characterization of erythrocyte, or red blood cell (RBC), EVs from healthy individuals and from patients with hereditary spherocytosis (HS) due to ankyrin deficiency. While these EVs are packed with proteins, their response to indentation resembles that of fluid liposomes lacking proteins. The bending modulus of RBC EVs of healthy donors is ~15 kbT, similar to the RBC membrane. Surprisingly, whereas RBCs become more rigid in HS, patient EVs have a significantly (~40%) lower bending modulus than donor EVs. These results shed light on the mechanism and effects of EV budding and might explain the reported increase in vesiculation of RBCs in HS patients.