Hematopoietic stem cell transplantation (HSCT) is a treatment method for a number of severe malignant and non-tumor diseases. Autologous (auto) and allogeneic (allo) HSCT improves outcomes in patients with solid and hematological malignancies. The toxicity of conditioning regimens before HSCT is often a limiting factor for successful transplant outcomes. The most common manifestations of visceral and tissue toxicity are epithelial (dermatological and mucosal) toxicity, hepatotoxicity, and neurotoxicity. Reducing the incidence of toxic complications of preparative regimens preceding HSCT is the optimization of accompanying therapy, and and individualized selection of doses of chemotherapy. In our study, among 119 HSCT cases performed in 2021–2022, treosulfan-containing preparative regimens were used. Dermatological toxicity was diagnosed in 80.0 %, mucositis – in 100 %, hepatotoxicity – in 18.5 % of observations, no neurological toxicity was recorded.

Germ cell tumors (GCTs) are a heterogeneous group of tumors that develop from pluripotent germ cells, diagnosed most often in infants, young children, adolescents and young adults, and are characterized by different localization, histological picture, clinical course and prognosis. Despite the fairly high efficiency of modern standard chemotherapy protocols for GCTs, the treatment of their relapses and refractory forms, which make up to 30–40 % of all GCTs and have an extremely unfavorable prognosis, is very difficult. Currently, there is no single strategy for the treatment of relapses and refractory forms of GCTs, however, the world and domestic literature presents data on the successful use of high-dose chemotherapy (HDCT) in such patients followed by autologous hematopoietic stem cell transplantation (auto-HSCT). To develop and optimize protocols for this therapy method, and therefore improve the treatment outcomes for patients with relapses and refractory forms of GCT, it is necessary to analyze a larger number of studies from various transplant centers working in this area. The article presents current literature data on the use of HDCT followed by auto-HSCT in patients with GCT, as well as a clinical case of successful 2 courses of HDCT with auto-HSCT in tandem mode in a child with a refractory form of GCT with subsequent maintenance of complete remission for 2 years.

High-dose chemotherapy (HDCT) followed by autologous hematopoietic stem cell transplantation (auto-HSCT) is a therapeutic option that allows potentiating the antitumor effect in patients with malignant neoplasms (MNs) belonging to the high-risk group. However, despite the effectiveness of this method, the risks of developing infectious and toxic complications in the early and late post-transplantation period are higher than the risks associated with treatment according to standard protocols and can significantly worsen the results of transplantation. We carried out a retrospective analysis of the results of auto-HSCT in a cohort of 156 patients with high-risk solid MNs treated at the L.A. Durnov Research Institute of Pediatric Oncology and Hematology, the N.N. Blokhin National Medical Research Center of Oncology of Ministry of Healthcare of the Russian Federation in 2020–2023. The study was approved by the Independent Ethics Committee and the Scientific Council of the N.N. Blokhin National Medical Research Center of Oncology. The study included 78 (50%) boys and 78 (50%) girls, the median age of the patients was 8 years 7 months (9 months – 17 years 8 months). Auto-HSCT was performed in 90 (57.7%) patients with neuroblastoma, 25 (16.0%) – with Ewing's sarcoma, 16 (10.3%) – with germ cell tumors, 13 (8.4%) – with nephroblastoma, 7 (4.5%) – with retinoblastoma, 3 (1.9%) – with medulloblastoma, 1 (0.6%) patient with pleuropulmonary blastoma and 1 (0.6%) patient with sialoblastoma. We used the following conditioning regimens: treosulfan + melphalan (n = 116), carboplatin + thiotepa + etoposide (n = 17), melphalan (n = 13), carboplatin + thiotepa + etoposide + cyclophosphamide (n = 10). Depending on the clinical indications and the treatment protocol used, 136 (87.2%) patients underwent one course of HDCT, and 20 (12.8%) patients underwent tandem HDCT. In most patients, the median recovery time for granulocytes and platelets was 11 (8–19) days and 14 (12–21) days, respectively. The most common infectious complications in patients after auto-HSCT were mucositis (89.1%), neutropenic enterocolitis (76.9%), febrile neutropenia (71.2%), less often: catheter-associated bloodstream infection (9%), pneumonia (14.1%), acute respiratory distress syndrome (0.6%). As regards toxic complications, all patients had emetic syndrome, 98 (62.8%) had dermatological toxicity, 9 (5.8%) had hemorrhagic cystitis, 116 (74.3%) had hepatic toxicity, 14 (9%) had neurotoxicity, 102 (65.4%) had moderate nutritional insufficiency. Episodes of hemorrhagic syndrome due to thrombocytopenia were observed in 44.2% of patients. After auto-HSCT, most patients develop chemotherapy-induced (including infectious) complications, which can not only significantly disrupt the patients’ well-being and quality of life, but also, depending on the severity, pose a threat to their life. The correct choice of conditioning regimen, effective collection of hematopoietic stem cells, complex accompanying therapy, timely diagnosis and treatment of complications can significantly improve the results of auto-HSCT in children with high-risk solid MNs.

Diagnosis, treatment and designing an adequate strategy of neuroblastoma (NB) therapy in children is still a complicated tasks for pediatric oncology and hematology. One of the key aspects of NB control is detection and monitoring of minimal residual disease.The authors make a concise review of the up-to-date methods, such as immunocytochemistry, fluorescent in situ hybridization (FISH), flow cytometry, the methods of qualitative and quantitative polymerase chain reaction (PCR) to estimate mRNA (RT-PCR and QRT-PCR), which are currently used for minimal residual disease detection in patients with NB. Disialoganglioside GD2, a specific NB marker, is traditionally determined by immunocytochemistry with fluorochromes that enhance its specificity, and by flow cytometry, as well. At present, FISH test is a gold standard for evaluation of the MYCN gen status in NB. A widely used multicolor flow cytometry method allows achieving high specificity of the analysis for NB diagnosis. RT-PCR may search for various targets to reveal NB cells, however, at the moment the only accepted immune target is tyrosine hydroxylase mRNA. Moreover, the studies established that quantitative QRT-PCR has more advantages than traditional qualitative RT-PCR, since this method allows a more accurate and quantitative detection of one or several mRNAs in clinical samples. The review discusses advantages and disadvantages of the main methods currently used for minimal residual disease evaluation of NB cells, such as RT-PCR, flow cytometry, FISH, etc. Comparative studies included multicolor flow cytometry with various combinations of CD9/CD81/CD56/CD45/GD2 monoclonal antibodies, conventional RT-PCR and quantitative QRT-PCR to reveal circulating/disseminated NB cells in the clinical samples of cancer patients and healthy volunteers.The authors analyze the results of various studies that compared accuracy and sensitivity of diagnostic methods such as RT-PCR, flow cytometry, FISH and some others. Despite the advantages of each method, the authors emphasize that multicolor flow cytometry is the optimal approach for the rapid and reliable detection of minimal residual disease and micrometastases of NB.

Background/Objectives: High-risk neuroblastoma (HR-NB) is a major cause of cancer-related death among children. The review aims to discuss various biochemical and genetic traits of neuroblastoma (NB) used for the potential of cell-based therapies. Methods: A comprehensive search was performed through MEDLINE, PubMed, Scopus, and ScienceDirect using various combinations of “neuroblastoma”, “tumor microenvironment (TME)”, “immune cells”, “non-immune cells”, “hematopoietic stem cell transplantation (HSCT)”, “autologous stem cell transplantation (ASCT)”, “natural killer cells (NK)”, “chimeric antigen receptor T cells (CAR-T)”, “CAR-NKT”, “tumor infiltrating lymphocytes (TIL)”, “bioinformatics”, and “neuro-antigens” in the published papers over the last decade. Reviews, systematic reviews, and clinical trials related to children’s NB were selected. The final set included 106 articles of interest. Results: Recent studies have shown that TME is crucial in determining the malignancy, immune evasion, and drug resistance of NB. Innate immune or non-immune cells play important roles in shaping the NB TME. Depleting or reprogramming TME factors can improve the effectiveness of immunotherapy. A number of clinical trials have studied and showed feasibility of using ASCT, NK cells, CAR-T, and CAR-NKT cells in the adoptive therapy for HR-NB. However, an unambiguous evaluation of the effectiveness of cell-based technologies in the HR-NB therapy is still complicated due to the lack of large randomized trials. Conclusions: The reported small and non-randomized studies that demonstrated controversial results cannot prove, undoubtedly, the promising potential of the cell-based technologies including ASCT, NKs, CAR-T, and CAR-NKT cells. Further randomized clinical trials, using the same treatment, will help determine the role in the multimodal treatment for HR-NB.

Currently, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment option for relapsed / refractory (R / R) acute leukemia (AL) and high-risk AL. In this article, we present our own experience of allo-HSCT in children with R / R AL. The study was approved by the Independent Ethics Committee and the Scientific Council of the N. N. Blokhin National Medical Research Center of Oncology. Fifty-one patients with R / R AL were included in the study: 32 patients had acute lymphoblastic leukemia (ALL), 17 patients had acute myeloid leukemia (AML) and 2 patients had biphenotypic leukemia (BL). All patients underwent allo-HSCT from January 2021 to October 2022. The median age was 8.7 years (5 months – 17 years). At the time of allo-HSCT, 26 patients were in the second (and further) remission, the rest were in the first clinical and hematologic remission (high-risk AML and refractory ALL). Twenty-one (41.2 %) patients received allo-HSCT from a haploidentical donor, 19 (37.2 %) patients underwent allo-HSCT from an HLA-matched related donor and 11 (21.6 %) patients – from an HLA-matched unrelated donor. Pre-transplant conditioning in ALL: 27 patients received regimens based on total body irradiation at a dose of 12 Gy, 4 patients received busulfan-based conditioning regimens, and in 1 patient we used treosulfan. In AML and BL, we used conditioning regimens based on treosulfan/thiotepa (n = 10), treosulfan/melphalan (n = 8) or busulfan / melphalan (n = 1). Bone marrow (in 14 patients) and peripheral blood stem cells (in 37 patients) were used as a source of hematopoietic stem cells. In haploidentical allo-HSCTs in order to prevent graft-versus-host disease (GVHD) we performed TCRab/CD19 depletion followed by additional administration of abatacept / tocilizumab / rituximab on day –1 in 15 patients, 6 patients received post-transplant cyclophosphamide. In transplantations from HLA-matched related and unrelated donors, patients received combined immunosuppressive therapy with abatacept and rituximab on day –1, and calcineurin inhibitors were used as basic immunosuppressive therapy. All patients engrafted with a median time to engraftment of 13 (range, 9 to 24) days after allo-HSCT. Eight (15.7 %) patients developed a relapse of AL at different times after HSCT (five of them are alive). At the median follow-up of 9 (5–25) months, the overall and disease-free survival survival rates were 76.4 % and 68.8 %, respectively, for patients with AL. Acute GVHD was observed in 72.5 % of children, grade 3–4 GVHD was observed in 5.3 % of patients, and 13.7 % of children developed chronic GVHD. Most patients developed infectious complications in the early post-transplant period: febrile neutropenia (96.0 %), reactivation of viremia (47.3 %,) oropharyngeal mucositis (78.4 %), acute cystitis (12.3 %). The overall mortality rate was 17.6 %. Late mortality was associated with a relapse of AL.