Severe aplastic anemia (SAA) is a bone marrow failure syndrome that can be treated with hematopoietic cell transplantation (HCT) or immunosuppressive (IS) therapy. A retrospective cohort of 56 children with SAA undergoing transplantation with fludarabine–cyclophosphamide–ATG-based conditioning (FluCyATG) was analyzed. The endpoints were overall survival (OS), event-free survival (EFS), cumulative incidence (CI) of graft versus host disease (GVHD) and CI of viral replication. Engraftment was achieved in 53/56 patients, and four patients died (two due to fungal infection, and two of neuroinfection). The median time to neutrophil engraftment was 14 days and to platelet engraftment was 16 days, and median donor chimerism was above 98%. The overall incidence of acute GVHD was 41.5%, and that of grade III-IV acute GVHD was 14.3%. Chronic GVHD was diagnosed in 14.2% of children. The probability of 2-year GVHD-free survival was 76.1%. In the univariate analysis, a higher dose of cyclophosphamide and previous IS therapy were significant risk factors for worse overall survival. Episodes of viral replication occurred in 33/56 (58.9%) patients, but did not influence OS. The main advantages of FluCyATG include early engraftment with a very high level of donor chimerism, high overall survival and a low risk of viral replication after HCT.

The prognosis of resistant or relapsing children with neuroblastoma remains very poor, and the search for new therapies is ongoing. In this analysis, we assessed the toxicity of a treosulfan, melphalan, and thiotepa (TMT) regimen in 17 children with recurrent or refractory neuroblastoma who underwent stem cell transplantation (SCT). For allogeneic SCT, fludarabine and antithymocyte globulin were added. The stem cell source was autologous in 8 patients, haploidentical in 8 patients, and a matched unrelated donor in 1 patient. The reported nonhematologic toxicities included grade 3 mucositis, grade 1 to 3 hypertransaminasemia, and in 3 patients, veno-occlusive disease. No neurologic, cardiac, or dermatologic toxicities were observed. The probability of overall survival (OS) in patients with primary resistance was superior to that in patients with relapsed disease (100% versus 22.6%; P = .046). Post-transplantation dinutuximab beta immunotherapy was associated with superior 5-year OS (66.7% versus 11.4%; P = .0007). The use of an allogeneic donor, previous autologous SCT with busulfan and melphalan, and pretreatment with high-dose metaiodobenzylguanidine therapy demonstrated no effect on outcomes. In 4 patients, TMT megatherapy alone was enough to achieve complete remission. The TMT conditioning regimen was well tolerated in heavily pretreated patients with neuroblastoma. The manageable toxicity and addition of new anticancer drugs with optional post-SCT immunotherapy or chemotherapy support further trials with the TMT regimen in patients with neuroblastoma.

Background. Unmanipulated haploidentical stem cell transplantation (haploSCT) with post-transplant cyclophosphamide is an option for patients with advanced hematologic malignancies. It offers a platform both for non-major histocompatibility complex-restricted alloimmunity due to killer-like immunoglobulin receptor (KIR)-mediated mechanisms of natural killer lymphocyte regulation and for classical T-cell mediated antileukemic effects. Objectives. The devastating long-term sequelae after total body irradiation (TBI) in children are encouraging omission of irradiation techniques in pediatric stem cell transplantations (SCT). Material and methods. Five children, 4 with acute leukemia and 1 with hemophagocytic lymphohistiocytosis, aged from 1 to 10 years, underwent haploSCT with post-transplantation cyclophosphamide. In all children, the conditioning regimen consisted of chemotherapy without TBI. The graft material was bone marrow (BM) in 4 cases and peripheral blood stem cells in 1 case. Three out of 5 leukemic patients showed better KIR haplotype associated with augmented alloreactivity. Results. Engraftment with complete donor chimerism was achieved in 4 patients, and 1 recipient died before leukocyte recovery. Three patients developed skin acute graft-versus-host-disease (aGvHD), 1 gut aGvHD and 1 liver aGvHD. In 2 recipients, chronic graft-versus-host-disease (cGvHD) was observed (1 limited and 1 extensive). The 4 engrafted patients were alive and in complete remission 3, 9, 32, and 36 months after transplantation. A T-cell count of 200 cells/uL was reached 90 days after haploSCT in all patients. Conclusions. HaploSCT with TBI-free protocols can be a viable option for heavily pretreated patients with advanced malignancies.

Donor-derived cell-free DNA (dd-cfDNA) is an emerging non-invasive biomarker of kidney allograft injury. Elevated dd-cfDNA has been associated with acute rejection, particularly antibody-mediated rejection; however, dd-cfDNA reflects graft-derived tissue injury rather than a specific alloimmune mechanism. Its interpretation may therefore be challenging in conditions characterized by endothelial and microvascular injury, such as atypical hemolytic uremic syndrome (aHUS). This retrospective observational study included 14 kidney transplant recipients who underwent their first kidney transplantation at Wroclaw Medical University between April and December 2022. Twelve recipients without aHUS and two recipients with aHUS were assessed at day 7 (D7), day 14 (D14), month 1 (M1), and month 2 (M2). Protocol biopsies were not systematically performed. In recipients without aHUS, median %dd-cfDNA declined from 0.72% (range, 0.26–2.33%) at D7 to 0.12% (range, 0.05–0.34%) at M2. In the two recipients with aHUS, values remained near or above 1% through M1 and declined at M2. No donor-specific antibodies against human leukocyte antigens (HLA) or clinically documented rejection occurred. Exploratory analyses did not identify a statistically significant association between %dd-cfDNA and serum creatinine (Spearman rho = 0.09, p = 0.541). These recipient-level observations suggest that early dd-cfDNA kinetics in the two recipients with aHUS differed from the declining pattern in the small comparison cohort, but they do not establish a group-level difference. Because protocol biopsies were not systematically performed, subclinical rejection could not be excluded. The findings should be considered hypothesis-generating and support cautious interpretation of universal dd-cfDNA thresholds in aHUS.

Donor-derived cell-free DNA (dd-cfDNA) is an emerging non-invasive biomarker of kidney allograft injury. Elevated dd-cfDNA has been associated with acute rejection, particularly antibody-mediated rejection; however, dd-cfDNA reflects graft-derived tissue injury rather than a specific alloimmune mechanism. Its interpretation may therefore be challenging in conditions characterized by endothelial and microvascular injury, such as atypical hemolytic uremic syndrome (aHUS). This retrospective observational study included 14 kidney transplant recipients who underwent their first kidney transplantation at Wroclaw Medical University between April and December 2022. Twelve non-aHUS recipients with stable renal function and two recipients with aHUS were assessed. Plasma samples were collected at four early post-transplant time points: day 7 (D7), day 14 (D14), month 1 (M1), and month 2 (M2). dd-cfDNA was measured using next-generation sequencing with the AlloSeq cfDNA assay. Donor-specific anti-HLA antibodies (DSA) were assessed using single-antigen bead testing. In non-aHUS recipients, median %dd-cfDNA declined from 0.72% [0.28%, 2.33%] at D7 to 0.12% [0.05%, 0.34%] by M1. In contrast, recipients with aHUS demonstrated persistently elevated dd-cfDNA values fluctuating around 1% [0.88%, 1.14%] during the first month of follow-up. No DSA were detected in any patient during the observation period. No apparent correlation was observed between %dd-cfDNA and serum creatinine in this small cohort. In this preliminary observational study, kidney transplant recipients with aHUS showed persistently elevated early post-transplant dd-cfDNA despite the absence of detectable DSA, absence of clinically documented rejection, and preserved graft function during follow-up. These findings suggest that universal dd-cfDNA thresholds may require cautious interpretation in aHUS. Larger biopsy-anchored studies integrating complement and endothelial injury markers are needed to clarify whether dd-cfDNA elevation in aHUS reflects alloimmune injury, complement-mediated microvascular injury, or overlapping mechanisms.