Background/Aim: Cytomegalovirus (CMV) infection is one of the major causes of morbidity following hematopoietic cell transplantation (HCT). Allogeneic HCT (allo-HCT) recipients are at the highest risk of clinically significant CMV reactivation. While letermovir has been approved for prophylactic use in CMV seropositive adults, reports on pediatric data are very limited. The objective of the study was to examine the use of letermovir for prophylaxis from CMV infection in children undergoing allo-HCT in a single center. Patients and Methods: This retrospective matched-pair analysis study included 39 CMV-seropositive pediatric patients undergoing allo-HCT receiving letermovir as a primary prophylaxis for CMV infection on a compassionate-use basis (LMV group, n=13) or not (control group, n=26). There were no differences in basic characteristics between the analyzed groups. Among patients of the study group, 12 received primary prophylaxis with letermovir from day +1 after HCT. One patient, previously treated with ganciclovir received secondary prophylaxis from day +18. Results: Prophylactic dose of letermovir was adjusted to cyclosporine co-administration, varied in between 120-480 mg, and given orally, once daily. No CMV reactivation was observed during administration of letermovir. Cumulative incidence of CMV reactivation was significantly higher for the control group not receiving prophylaxis. Of the 13 patients of the study group, three died; however, deaths were not attributable to CMV infection. We did not observe any toxicities related to letermovir. Conclusion: Our data support letermovir prophylaxis efficacy and safety in pediatric patients after allo-HCT. Compared with the historical group, prophylactic use of letermovir decreased the number of CMV reactivations in children.

Infections are the main reason for mortality during acute leukaemia treatment and invasive aspergillosis (IA) is a major concern. Allogeneic stem cell transplantation (alloSCT) is a standard therapy and often is the only live-saving procedure in leukaemia patients. The profound immunodeficiency occurring after alloSCT led to high IA-associated mortality in the past. Therefore, patients with IA were historically considered transplant-ineligible. Recently, there has been improvement of anti-fungal management including novel anti-fungal agents. As a result, more leukaemia patients with IA are undergoing alloSCT. Outcome has not been prospectively assessed. We performed a prospective study in acute leukaemia patients undergoing alloSCT to analyse the impact of a prior history of probable or proven IA (pre-SCT IA). The primary endpoint was 1-year non-relapse mortality (NRM). Relapse free survival and overall survival were analysed as secondary endpoints. 1439 patients were included between 2016 and 2021. The incidence of probable or proven pre-SCT IA was 6.0% (n = 87). The cumulative incidence of 1-year NRM was 17.3% (95% CI 10.2-26.0) and 11.2% (9.6-13.0) for patients with and without pre-SCT IA. In multivariate analyses the hazard ratio (HR) for 1-year NRM was 2.1 (1.2-3.6; p = 0.009) for patients with pre-SCT IA. One-year relapse-free survival was inferior in patients with pre-SCT IA (59.4% [48.3-68.9] vs. 70.4 [67.9-72.8]; multivariate HR 1.5 [1.1-2.1]; p = 0.02). Consequently, 1-year overall survival was lower in patients with pre-SCT IA: (68.8% [57.8-77.4] vs. 79.0% [76.7-81.1]; multivariate HR 1.7 [1.1-2.5]; p = 0.01). Pre-SCT IA remains to be significantly associated with impaired alloSCT outcome. On the other hand, more than two thirds of patients with pre-SCT IA were alive at one year after alloSCT. IA is not anymore an absolute contraindication for alloSCT because the majority of patients with IA who undergo alloSCT benefit from this procedure. There was no external funding source for this study.

Background: Immunocompromised children with malignancies or after hematopoietic cell transplantation (HCT) often deteriorate before conventional cultures identify a pathogen. Next-generation sequencing (NGS) promises faster, broader detection, yet its clinical impact in pediatric oncology remains unclear. This review aimed to assess the diagnostic performance and clinical utility of NGS in this population. Methods: We searched PubMed, Embase, and Scopus from January 2010 to April 2025 for studies evaluating NGS (metagenomic, targeted, or whole-genome sequencing) in pediatric oncology or HCT patients meeting predefined eligibility criteria. Duplicate screening, data extraction, and Joanna Briggs Institute risk-of-bias appraisal were performed. Heterogeneity precluded formal meta-analysis; findings were synthesized using narrative synthesis complemented by limited quantitative analyses. The protocol was not registered. Results: Twenty-four studies (≥2700 children; 2019–2025) met inclusion criteria. Metagenomic NGS (mNGS) was the most common approach, applied to blood/plasma (46%), bronchoalveolar fluid (BALF) (21%), and other fluids. In culture-negative sepsis or persistent febrile neutropenia, mNGS detected pathogens in 69–86% of episodes versus 18–56% for culture/polymerase chain reaction (PCR). Described in limited studies, early (<48 h) testing shortened fever by ~1.5 days and cut antimicrobial costs by 25–30%. Across studies, treatment was escalated, de-escalated, or discontinued in a median of 63% of mNGS-positive cases. Whole-genome sequencing (WGS) identified 18 silent transmission clusters and resolved a multidrug-resistant Acinetobacter baumannii outbreak within hours. Conclusions: NGS benefits pediatric hemato-oncology by accelerating pathogen-directed therapy, supporting antimicrobial stewardship, and enhancing outbreak surveillance. Despite cost and standardization barriers, evidence supports its use in selected high-risk patients.

Introduction: Leukemia belong to 31% of all childhood malignancies. Acute lymphoblastic leukemia (ALL) is the most frequent type of pediatric leukemia accounting for 80–85% of all cases. Progress in diagnostics and therapy of leukemia is dependent on international cooperation. The objective of the study was the analysis of non-hematological toxicity during intensive chemotherapy according to two consecutive intercontinental protocols.Patients and methods: A total number of 210 children diagnosed for ALL who were treated in single center between 2002 and 2018 were divided in two groups defined by therapeutic protocol: ALL IC-BFM 2002 (group 1) and ALL IC-BFM 2009 (group 2). Data were entered prospectively from 2002 into international ALL IC-BFM 2002 and ALL IC-BFM 2009 registry. Non-hematological toxicity was analyzed according to the criteria followed in protocols, compatible with CTCAE criteria.Results: The most frequent toxicities included hepatic toxicity with transaminitis and hyperbilirubinemia, infections, oral mucositis and gut toxicity with vomiting, and/or diarrhea. Non-hematological toxicity episodes calculated as a ratio per patient were comparably often observed in both the groups; however, the distribution was different. There were more grade III and less grade II toxicities. This was mainly related to significant increase in the rates of infections and transaminitis. However, there was a significant decrease in vomiting and central and peripheral neurotoxicity.Conclusions: Intensive treatment of ALL is burdened with frequent severe toxic and infectious complications. Further progress in therapy of pediatric ALL is dependent on sophisticated supportive therapy and very well experienced and knowledgeable therapeutic team.

Background/Objectives: The objective of this study was to analyze the clinical and laboratory features, management, outcomes, and complications of PRES in children with malignancies or following hematopoietic cell transplantation (HCT). Methods: This was a multicenter retrospective analysis of PRES episodes diagnosed between 2014 and 2022 in Polish pediatric hematology and oncology (PHO) centers and HCT units. The study included 438 patients treated for malignancy or post-HCT: 120 with PRES (study group) and 318 without PRES (control group). Results: PRES was diagnosed in children aged 1.7–16.5 years (median = 7.7 years). The most common underlying diagnosis was ALL (76.7%; n = 92). Symptoms of PRES included disturbances of consciousness (84.2%), seizures (80.0%), hypertension (74.2%), apathy (64.2%), abdominal pain (45.0%), visual disturbances (28.3%), and headaches (26.7%). Electrolyte abnormalities were observed in 75.0% of children, most commonly hyponatremia (49.2%) and hypokalemia (37.5%). Children with PRES were more likely to require admission to the intensive care unit (ICU) than controls (50.0% vs. 29.6%, p < 0.001). The most frequent long-term complications of PRES were hypertension (22.5%) and epilepsy (20.8%). Among PHO patients, those with PRES had significantly lower DFS (76.7% vs. 93.7%, p < 0.001) and OS (79.2% vs. 93.4%, p < 0.001). In the HCT group, PRES was also associated with lower DFS (40.0% vs. 83.3%, p = 0.012) and OS (40.0% vs. 77.8%, p = 0.047). Conclusions: PRES is a significant complication of oncological and transplant treatment in children. Its occurrence was associated with worse overall and disease-free survival. We proposed a predictive index for PRES, diagnostic criteria, and a revised name for this syndrome.

Background: Pseudomonas aeruginosa (PSA) infections are associated with a high recurrence rate and high mortality in immuno-compromised patients. There are limited studies regarding pediatric hematopoietic cell transplantation recipients. Aim: The nationwide multicenter study was conducted to analyze the epidemiology of PSA infections in children treated with chemotherapy (PHO, pediatric hematology and oncology) or undergoing hematopoietic allogeneic or autologous cell transplantation (HCT) in the period 2014–2023. Methods: We retrospectively analyzed the clinical and microbiological data of children who underwent anticancer therapy or hematopoietic cell transplantation in 17 Polish PHO centers and six pediatric HCT centers. The data were collected in two-year intervals. Results: During the 10-year study period, a total of 1629 HCTs (both autologous and allogeneic) and 9614 children newly diagnosed with neoplasms were analyzed. The cumulative incidence of PSA infection was similar in both groups (6.71% in PHO vs. 6.32% in HCT, p = 0.624). The total number of PSA bloodstream infections was comparable in the PHO and HCT groups (31.9% vs. 26.2%; p = 0.223). In both analyzed groups, the antipseudomonal drugs of choice were as follows: meropenem, ceftazidime, and tazobactam/piperaciline in combination with other antibiotics. In the HCT group, high rates of meropenem (20.4%) and tazobactam/piperaciline (18.4%) non-susceptibility were observed. This led to colistin therapy in 5.3% of patients. There was no difference in the median antibiotic therapy time in both groups; however, the survival rates from PSA infection were significantly lower in the HCT group (89.3% vs. 96.0%, p = 0.004). Conclusions: Although the risk of infection and the occurrence of resistant bacterial strains in HCT patients were comparable with those in PHO patients, the outcome of PSA infections was better in the PHO setting.