Proposed Therapeutic Range of Treosulfan in Reduced Toxicity Pediatric Allogeneic Hematopoietic Stem Cell Transplant Conditioning: Results From a Prospective Trial

Treosulfan is given off‐label in pediatric allogeneic hematopoietic stem cell transplant. This study investigated treosulfan's pharmacokinetics (PKs), efficacy, and safety in a prospective trial. Pediatric patients (n = 87) receiving treosulfan‐fludarabine conditioning were followed for at least 1 year posttransplant. PKs were described with a two‐compartment model. During follow‐up, 11 of 87 patients died and 12 of 87 patients had low engraftment (≤ 20% myeloid chimerism). For each increase in treosulfan area under the curve from zero to infinity (AUC_(0‐∞)) of 1,000 mg hour/L the hazard ratio (95% confidence interval) for mortality increase was 1.46 (1.23–1.74), and the hazard ratio for low engraftment was 0.61 (0.36–1.04). A cumulative AUC_(0‐∞) of 4,800 mg hour/L maximized the probability of success (> 20% engraftment and no mortality) at 82%. Probability of success with AUC_(0‐∞) between 80% and 125% of this target were 78% and 79%. Measuring PK at the first dose and individualizing the third dose may be required in nonmalignant disease.

Delaying haematopoietic stem cell transplantation in children with viral respiratory infections reduces transplant-related mortality

Viral respiratory infections (VRIs) contribute to the morbidity and transplant‐related mortality (TRM) after allogeneic haematopoietic stem cell transplantation (HSCT) and strategies to prevent and treat VRIs are warranted. We monitored VRIs before and after transplant in children undergoing allogeneic HSCT with nasopharyngeal aspirates (NPA) and assessed the impact on clinical outcome. Between 2007 and 2017, 585 children underwent 620 allogeneic HSCT procedures. Out of 75 patients with a positive NPA screen (12%), transplant was delayed in 25 cases (33%), while 53 children started conditioning with a VRI. Patients undergoing HSCT with a positive NPA screen had a significantly lower overall survival (54% vs. 79%) and increased TRM (26% vs. 7%) compared to patients with a negative NPA. Patients with a positive NPA who delayed transplant and cleared the virus before conditioning had improved overall survival (90%) and lower TRM (5%). Pre‐HSCT positive NPA was the only significant risk factor for progression to a lower respiratory tract infection and was a major risk factor for TRM. Transplant delay, whenever feasible, in case of a positive NPA screen for VRIs can positively impact on survival of children undergoing HSCT.

Contrast-enhanced ultrasound for multiple liver lesions after bone marrow transplant in a child with leukaemia: Multifocal focal nodular hyperplasia

We present a case of a two-year-old girl in which liver lesions were characterised on contrast-enhanced ultrasound as multifocal focal nodular hyperplasia. This child had previously undergone haematopoietic stem cell transplantation for juvenile myelomonocytic leukaemia and was suspected to have hepatobiliary graft versus host disease. Liver biopsy was performed to confirm the unexpected focal nodular hyperplasia and look for concurrent graft versus host disease. Focal nodular hyperplasia was histologically confirmed on a background of diffuse liver damage in keeping with polypharmacotherapy, steatosis and sepsis. An element of graft versus host disease was not excluded but was not confidently shown in the sample of the lesion. This case report describes and illustrates how contrast-enhanced ultrasound may be of use to further assess hepatic lesions in a complex case of multifactorial hepatic pathology. Radiologists, haematologists and pathologists should be aware that multifocal focal nodular hyperplasia is part of the differential diagnosis of liver lesions in a child with liver damage due to complex disease and treatment. Biopsy remains the gold standard, if there is a concurrent clinical suspicion of graft versus host disease.

Dendritic cell reconstitution is associated with relapse-free survival and acute GVHD severity in children after allogeneic stem cell transplantation

DCs are potent APCs and key regulators of innate and adaptive immunity. After allo-SCT, their reconstitution in the peripheral blood (PB) to levels similar to those in healthy individuals tends to be slow. We investigate the age- and sex-dependant immune reconstitution of myeloid (mDC) and plasmacytoid DC (pDC) in the PB of 45 children with leukaemia or myelodysplastic syndrome (aged 1-17 years, median 10) after allo-SCT with regard to relapse, acute GVHD (aGVHD) and relapse-free survival. Low pDC/μL PB up to day 60 post SCT are associated with higher incidence of moderate or severe aGVHD (P=0.035), whereas high pDC/μL PB up to day 60 are associated with higher risk of relapse (P<0.001). The time-trend of DCs/μL PB for days 0-200 is a significant predictor of relapse-free survival for both mDCs (P<0.001) and pDCs (P=0.020). Jointly modelling DC reconstitution and complications improves on these simple criteria. Compared with BM, PBSC transplants tend to show slower mDC/pDC reconstitution (P=0.001, 0.031, respectively), but have no direct effect on relapse-free survival. These results suggest an important role for both mDCs and pDCs in the reconstituting immune system. The inclusion of mDCs and pDCs may improve existing models for complication prediction following allo-SCT.

Myeloid and plasmacytoid dendritic cells: reference ranges in the peripheral blood of healthy children

To date, few publications report on dendritic cells values in healthy children and mostly are found as control groups in studies focused on either allergic and autoimmune diseases or malignancies. This report provides an overview of 8 publications regarding absolute dendritic cells quantification in the peripheral blood of healthy children by using minimum manipulated samples processed within 24 hours.

Age-matched dendritic cell subpopulations reference values in childhood

Dendritic cells (DCs) are the most potent antigen-presenting cells and are the key link between the innate and adaptive immune response. Only a few reports with study populations of up to 50 individuals have been published with age-based reference values for DC subpopulations in healthy children. Therefore, we aimed to establish reference ranges in a larger study population of 100 healthy children, which allowed age-matched subgroups. Most previous studies were performed using a dual-platform approach. In this study, a single-platform approach in a lyse no-wash procedure was used. DC subpopulations were defined as follows: CD45(+) CD85k(+) HLA-DR(+) CD14(-) CD16(-) CD33(+) cells as myeloid DCs (mDCs) and CD45(+) CD85k(+) HLA-DR(+) CD14(-) CD16(-) CD123(+) cells as plasmacytoid DCs (pDCs). Reference ranges were established using a semi-parametric regression of age-matched absolute and relative DC counts. We found a significant decline with increasing age in the medians of mDCs (P = 0.0003) and pDCs per μl peripheral blood (PB) (P = 0.004) and in the 50%, 90% and 95% reference ranges. We also identified significantly lower absolute cell counts of mDCs per μl PB in girls than in boys for all age groups (P = 0.0015). Due to the larger paediatric study population and single-platform approach, this study may give a more precise overview of the normal age-matched development of DC subpopulations and may provide a basis for analyzing abnormal DC counts in different illnesses or therapies such as post stem cell transplantation.