Background: Apheresis in children with low body weight is technically limited by their tolerance of the extracorporeal blood volume. Study design and methods: This paper presents a single-center experience with 23 procedures in 12 children with weights between 5.2 and 9.5 kg using the Spectra Optia mononuclear cell (MNC) protocol with blood priming. Results: The average procedure duration was 158 minutes, and the median processed blood volume was 316 mL/kg. The white blood cell (WBC), platelet (PLT), and hemoglobin (HGB) values showed a downward trend with increased volume of processed blood. The post-apheresis HGB concentration was increased in all procedures due to initial priming with packed red blood cells (PRBCs), but this effect disappeared at a level of~400 mL of processed blood/kg. The median volume of the cellular product was 36 mL, the WBC count was 153 K/μL, the hematocrit (HCT) was 1.5%, the PLT count was 602 K/μL, the WBC collection efficacy (CE2) was 13.2%, and the PLT CE2 was 9.5%. The median CD34+ CE2 was 28%, and interpolation of the CD34+ CE2 yielded a Y-intercept value of 32%.Higher pre-collection CD34+ counts resulted in higher CD34+ yields. No correlation was found between the pre-collection CD34+ results and CD34+ CE2. CONCLUSION: The analyzed data demonstrated the feasibility and safety of apheresis in very low-weight children. The laboratory abnormalities were asymptomatic and citrate toxicity was mild. Visual control of clogging with manual adjustment of the citrate infusion rate is important to reduce exposure to citrate. K E Y W O R D S apheresis, low-weight, pediatric

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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.

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.

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