Pre-Exposure Prophylaxis and Treatment with Tixagevimab/Cilgavimab for COVID-19 among Immunocompromised Pediatric Patients.

Background: Patients treated with hemato-oncological malignancies (HO) or undergoing cellular therapies such as hematopoietic stem cell transplantation (HSCT) or chimeric antigen receptor T cells (CAR-T) were significantly affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite the success of SARS-CoV-2 vaccination, immunocompromised patients remain at increased risk for severe coronavirus disease (COVID-19), rendering this group of population a high priority for additional prevention and treatment options. Tixagevimab and Cilgavimab (TIXA/CILGA, AZD7442, Evusheld®) is a combination of two fully human, long-acting monoclonal antibodies. TIXA/CILGA have been approved as pre-exposure prophylaxis and treatment in patients at risk of severe disease with impaired vaccine response. Our objective was to describe the efficacy and safety among immunocompromised pediatric patients. Methods: This was an observational multicenter cohort study of immunocompromised pediatric patients receiving TIXA/CILGA conducted at nine Polish centers of Pediatric Oncology, Hematology and Bone Marrow Transplantation. We analyzed patients in two groups; those treated with HO and those undergoing cellular therapies: HSCT or CAR-T cells. In addition, two other cohorts were identified: patients given TIXA/CILGA as pre-exposure prophylactic and therapeutic intervention. Results: A total of 78 patients were evaluated during the study period: 69 (88.5%) received TIXA/CILGA as pre-exposure prophylaxis and 9 (11.5%) as a treatment strategy. A total of 52 (66.6%) patients were treated with standard chemotherapy at HO departments; 21 (27%) underwent HSCT, and 5 (6.4%) received CAR-T cell therapy. All children with COVID-19 receiving TIXA/CILGA presented a mild degree of severity. The most common clinical manifestations were fever, cough and coryza. At least one adverse event (AE) was reported in two (3.8%) patients excluding standard injection site reactions. Reported AEs were mild or moderate in intensity. One child reported mild myalgia and one reported moderate bone pain and weakness. Conclusions: In our observational multicenter cohort study, we explored the use of TIXA/CILGA as pre-exposure prophylaxis and treatment for COVID-19 among immunocompromised pediatric patients. While our findings suggest a potential benefit in preventing and managing COVID-19 in this vulnerable population, it is important to note the study's non-comparative design. Our results highlight the need for well-designed clinical trials to confirm these observations and further assess the efficacy and safety of TIXA/CILGA in immunocompromised children.

Treatment Outcomes of Adolescents Compared to Younger Pediatric Patients with Acute Myeloid Leukemia: Do They Need a Special Approach?

BACKGROUND: The reports of studies that compare the survival of adolescents and young adults with younger children with acute myeloid leukemia (AML) are contradictory. PATIENTS AND METHODS: We retrospectively analyzed 220 AML patients aged 0-18 years treated in pediatric oncologic centers in Poland from 2015 to 2022. The evaluated group included 31 infants (below 1 year), 91 younger children (1-9.9 years), 59 older children (10-14.9 years), and 39 adolescents (15-18 years). RESULTS: A 5-year overall survival for adolescents was not significantly inferior compared to younger and older children (74.3 ± 7.6% vs. 80.5 ± 4.4% vs. 77.9 ± 5.1, p = 0.243). However, relapse-free survival was lower in adolescents compared to younger children (76.5 ± 7.8% vs. 65.7 ± 9.0%, p = 0.049), and treatment-related mortality tended to be higher (10.3% vs. 4.4%, p = 0.569). In the univariate analysis, high-risk genetics [HR, 2.0 (95% CI 1.1-3.6; p = 0.014)] and a leukocyte count at diagnosis above 100,000/µL [HR, 2.4 (95% CI 1.3-4.6; p = 0.004)] were found to be unfavorable prognostic factors for survival. CONCLUSIONS: Although we have not found that age over 15 years is an unfavorable factor for overall survival, the optimal approach to therapy in adolescents, as in other age groups, is to adjust the intensity of therapy to individual genetic risk and introduce targeted therapies when indicated.

Hematopoietic stem cell transplantation for pediatric patients with non-anaplastic peripheral T-cell lymphoma. An EBMT pediatric diseases working party study.

Peripheral T-cell lymphomas (PTCL) other than anaplastic large-cell lymphoma are rare in children, and the role of hematopoietic stem cell transplantation (HSCT) has not been clarified yet. In a retrospective analysis of registry-data of the European Society for Blood and Marrow Transplantation we analyzed 55 patients aged < 18 years who received allogeneic (N = 46) or autologous (N = 9) HSCT for PTCL. Median age at HSCT was 13.9 years; 33 patients (60%) were in first remission, and 6 (19%) in progression at HSCT. Conditioning was myeloablative in 87% of the allogeneic HSCTs and in 27 (58.7%) based on total body irradiation. After allogeneic HSCT the 5-year overall- and progression-free survival was 58.9% (95% CI 42.7-71.9) and 52.6% (95% CI 36.8-66.1), respectively. 5-year relapse incidence was 27.6% (95% CI 15.1-41.6), the non-relapse mortality rate was 19.8% (95% CI 9.7-32.6). Five of the six patients with progression at HSCT died. Seven of nine patients after autologous HSCT were alive and disease-free at last follow-up. Our data suggest a role of allogeneic HSCT in consolidation-treatment of patients with high-risk disease, who reach at least partial remission after primary- or relapse-therapy, whereas patients with therapy-refractory or progressive disease prior to transplantation do not profit from HSCT.

Incidence of bacterial and fungal infections in Polish pediatric patients with acute lymphoblastic leukemia during the pandemic.

The most common complications related to the treatment of childhood acute lymphoblastic leukemia (ALL) are infections. The aim of the study was to analyze the incidence and mortality rates among pediatric patients with ALL who were treated in 17 Polish pediatric hematology centers in 2020-2021 during the pandemic. Additionally, we compared these results with those of our previous study, which we conducted in the years 2012-2017. The retrospective analysis included 460 patients aged 1-18 years with newly diagnosed ALL. In our study, 361/460 (78.5%) children were reported to have microbiologically documented bacterial infections during chemotherapy. Ten patients (2.8%) died due to sepsis. Fungal infections were reported in 99 children (21.5%), of whom five (5.1%) died due to the infection. We especially observed an increase in bacterial infections during the pandemic period compared to the previous study. The directions of our actions should be to consider antibiotic prophylaxis, shorten the duration of hospitalization, and educate parents and medical staff about complications (mainly infections) during anticancer therapy. It is necessary to continue clinical studies evaluating infection prophylaxis to improve outcomes in childhood ALL patients.

Characteristics and Outcome of FLT3-ITD-Positive Pediatric Acute Myeloid Leukemia-Experience of Polish Pediatric Leukemia and Lymphoma Study Group from 2005 to 2022.

BACKGROUND: The FMS-like tyrosine kinase 3 (FLT3) gene mutated in 10-15% of pediatric acute myeloid leukemia (AML) is associated with an inferior outcome. The aim of the study was to analyze the outcome and characteristics of FLT3-ITD-positive pediatric AML. METHODS: We retrospectively analyzed the nationwide pediatric AML database from between 2005 and 2022. FLT3-ITD was found in 54/497 (10.7%) patients with available analysis. Three consecutive treatment protocols were used (AML-BFM 2004 Interim, AML-BFM 2012 Registry, AML-BFM 2019 recommendations). RESULTS: Probabilities of 5-year overall (OS), event-free (EFS) and relapse-free survival were significantly lower in the FLT3-ITD-positive patients compared to FLT3-ITD-negative (0.54 vs. 0.71, p = 0.041; 0.36 vs. 0.59, p = 0.0004; 0.47 vs. 0.70, p = 0.0029, accordingly). An improvement in the outcome was found in the analyzed period of time, with a trend of better survival in patients treated under the AML-BFM 2012 and AML-BFM 2019 protocols compared to the AML-BFM 2004 protocol (5-year EFS 0.52 vs. 0.27, p = 0.069). There was a trend of improved outcomes in patients treated with FLT3 inhibitors (n = 9, 2-year EFS 0.67 vs. 0.33, p = 0.053) and those who received stem cell transplantation (SCT) (n = 26; 5-year EFS 0.70 vs. 0.27, p = 0.059). The co-occurrence of the WT1 mutation had a dismal impact on the prognosis (5-year EFS 0.23 vs. 0.69, p = 0.002), while the NPM1 mutation improved survival (5-year OS 1.0 vs. 0.44, p = 0.036). CONCLUSIONS: It seems that SCT and FLT3 inhibitors have a beneficial impact on the prognosis. Additional genetic alterations, like the WT1 and NPM1 mutations, significantly influence the outcome.

Cytogenetic findings in Polish patients with suspected Fanconi anemia.

BACKGROUND: The high sensitivity of cells of Fanconi anemia (FA) patients to DNA cross-linking agents (clastogens), such as mitomycin C (MMC), was used as a screening tool in Polish children with clinical suspicion of FA. OBJECTIVES: The aim of the study was to compare chromosome fragility between 3 groups, namely non-FA, possible mosaic FA and FA patients. MATERIAL AND METHODS: The study included 100 children with hematological manifestations and/or congenital defects characteristic of FA, and 100 healthy controls. Blood samples obtained from participants were analyzed using an MMC-induced chromosomal breakage test. RESULTS: Patients with clinical suspicion of FA were divided into 3 subgroups based on the MMC test results, namely FA, possible mosaic FA and non-FA. Thirteen out of 100 patients had a true FA cellular phenotype. The mean value of MMC-induced chromosome breaks/cell for FA patients was higher than for non-FA patients (6.67 ±3.92 compared to 0.23 ±0.18). In addition, the percentage of cells with spontaneous aberrations was more than 9 times higher in FA patients than in non-FA patients. CONCLUSIONS: Our results confirmed that the MMC sensitivity test distinguishes between individuals affected by FA, those with possible somatic mosaicism, and patients with bone marrow failure for other reasons, who were classified as non-FA in the first diagnostic step. However, a definitive differential diagnosis requires follow-up mutation testing and chromosome breakage analysis of skin fibroblasts.

Pediatric Acute Myeloid Leukemia Post Cytotoxic Therapy-Retrospective Analysis of the Patients Treated in Poland from 2005 to 2022.

Acute P./myeloid leukemia post cytotoxic therapy (AML-pCT) is rare complication of cancer treatment in childhood. The objective of the study was to identify clinical characteristics and provide an analysis of the outcomes in pediatric AML-pCT. We retrospectively analyzed the data of 40 children with AML-pCT, treated from 2005 to 2020 within the Polish Pediatric Leukemia and Lymphoma Study Group. The most common primary malignancies were acute lymphoblastic leukemia (32.5%) and brain tumors (20%). The median latency period was 2.9 years (range: 0.7-12.9). Probabilities of overall (OS), event-free (EFS), and relapse-free survival (RFS) in the whole cohort were 0.49 ± 0.08, 0.43 ± 0.08, and 0.64 ± 0.10, respectively. Significant improvements in outcomes were observed in patients treated from 2015-2022 (two induction cycles followed by stem cell transplantation-SCT in 69% of patients) compared to 2005-2014 (four induction cycles followed by SCT in 49% of patients). The probability of EFS increased from 0.30 ± 0.10 to 0.67 ± 0.12 (p = 0.07) and RFS increased from 0.46 ± 0.11 to 1.0 (p = 0.01). The poorest outcome (OS and EFS 0.25 ± 0.20) was in AML post brain tumor, mainly due to deaths from toxicities. To conclude, treatment results achieved in patients with AML-pCT treated from 2015-2022, with two induction cycles followed by immediate SCT, were better than those reported by other authors, and comparable to the results in de novo AML.

Characteristics and treatment results of refractory and relapsed acute myeloid leukaemia in paediatric patients treated in Polish Paediatric Leukaemia/Lymphoma Study Group institutions according to the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 and a review of novel treatment possibilities in paediatric acute myeloid leukaemia.

Introduction: This study aimed to present the clinical features and results of treatment of patients diagnosed with refractory or relapsed acute myeloid leukaemia (AML) in Polish Paediatric Leukaemia/Lymphoma Study Group (PPL/LSG) institutions, treated in accordance with the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012, as their first-line therapy. Material and methods: The outcome data of 10 patients with refractory AML (median age 9.5 years) and 30 with relapsed AML (median age 12 years) were analysed retrospectively. Re-induction was usually based on idarubicin, fludarabine, and cytarabine along with allogeneic haematopoietic stem cell transplant (allo-HSCT) in 5 patients with refractory AML and 7 relapsed AML children. Results: 37.5% (3/8) of refractory AML patients achieved second complete remission second complete remission (CRII). One of ten patients (1/10; 10%) was alive and stayed in complete remission for 34 months after the allo-HSCT. The probability of 3-year event-free survival (pEFS) in this group was 0.125 ±0.11. In the group of relapsed AML patients, the CRII was achieved in 9 patients (34%), and the probability of survival was: pEFS = 0.24 ±0.08; probability overall survival (pOS) = 0.34 ±0.09, with significantly better results achieved in patients who underwent allo-HSCT (pOS = 0.54 ±0.14 vs. 0.08 ±0.08, p < 0.0001). Conclusions: The prognosis of refractory AML and the first AML recurrence in children who were first-line treated in PPL/LSG centres according to Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 is poor. Failures of re-induction treatment particularly result from difficulties in achieving remission. Allogeneic HSCT improves prognosis in children with refractory and first recurrent AML, under the condition it is performed in complete remission. Novel therapeutic approaches are needed to increase the remission rate and improve the outcomes.

Blinatumomab Prior to CAR-T Cell Therapy-A Treatment Option Worth Consideration for High Disease Burden.

The optimal bridging therapy before CAR-T cell infusion in pediatric relapsed or refractory B-cell precursor acute lymphoblastic leukemia (r/r BCP-ALL) still remains an open question. The administration of blinatumomab prior to CAR-T therapy is controversial since a potential loss of CD19+ target cells may negatively impact the activation, persistence, and, as a consequence, the efficacy of subsequently used CAR-T cells. Here, we report a single-center experience in seven children with chemorefractory BCP-ALL treated with blinatumomab before CAR-T cell therapy either to reduce disease burden before apheresis (six patients) or as a bridging therapy (two patients). All patients responded to blinatumomab except one. At the time of CAR-T cell infusion, all patients were in cytological complete remission (CR). Four patients had low positive PCR-MRD, and the remaining three were MRD-negative. All patients remained in CR at day +28 after CAR-T infusion, and six out of seven patients were MRD-negative. With a median follow-up of 497 days, four patients remain in CR and MRD-negative. Three children relapsed with CD19 negative disease: two of them died, and one, who previously did not respond to blinatumomab, was successfully rescued by stem cell transplant. To conclude, blinatumomab can effectively lower disease burden with fewer side effects than standard chemotherapeutics. Therefore, it may be a valid option for patients with high-disease burden prior to CAR-T cell therapy without clear evidence of compromising efficacy; however, further investigations are necessary.

Viral Infection Profile in Children Treated for Acute Lymphoblastic Leukemia-Results of Nationwide Study.

Viral infections can be a serious complication of therapy in children with acute lymphoblastic leukemia (ALL). In this study, we focused on the incidence and the profile of viral infection in children with ALL treated in 17 pediatric oncology centers in Poland in the two-year periods of 2018-2019 and 2020-2021. We also compared the frequency of viral infections in 2018-2019 to that in 2020-2021. In 2020-2021, a total of 192 children with ALL had a viral infection during intensive chemotherapy. A total number of 312 episodes of viral infections were diagnosed. The most common infections detected in the samples were: COVID-19 (23%), rhinovirus (18%), and respiratory syncytial virus (14%). COVID-19 and BK virus infections were the reason for the death 1% of all patients. In 2018-2019, a total of 53 ALL patients who had a viral infection were reported and 72 viral events were observed, mainly adenovirus (48.6%), rotavirus (31.9%), and herpes zoster (8.3%). No deaths were reported during this period. The cumulative incidence of viral infections in 2018-2019 was 10.4%, while for 2020-2021, it was 36.7%. In conclusion, a high incidence of COVID-19 infection was observed among pediatric patients with ALL in Poland. The mortality rate in our material was low. The viral profile in ALL children undergoing chemotherapy can be useful for clinicians to improve prophylactic and therapeutic strategies.

The efficacy and safety of allogeneic stem cell transplantation in Mevalonate Kinase Deficiency.

OBJECTIVES: Mevalonate kinase deficiency (MKD) is a rare autoinflammatory syndrome. Several reports have described allogeneic hematopoietic stem cell transplantation in severely affected patients, sometimes with promising results. In view of the scarcity of data, this study aims to analyse the efficacy and safety of allogeneic hematopoietic stem cell transplantation (HSCT) to give a more complete overview of this treatment. METHODS: This multicentre retrospective study on behalf of the European Society for Blood and Marrow Transplantation aimed to include all MKD patients who had undergone allogeneic HSCT. All centres related to EMBT and centres that have reported cases of allogeneic HSCT in the literature were contacted via the EBMT data office. RESULTS: We analyzed 9 patients (5 male). Treosulfan based conditioning was the most frequently used conditioning regimen. Engraftment occurred in all but one patient. Source of stem cells was cord blood (n = 2), peripheral blood stem cells (n = 4) and bone marrow (n = 5). Two patients needed a second transplantation due to an incomplete response or primary graft failure. Seven patients went into complete remission after stem cell transplantation. At final follow-up these patients reported no symptoms of MKD. Four patients suffered from grade II-IV acute graft-versus-host disease (GvHD). During follow-up two patients died due to transplantation related complications. CONCLUSION: In conclusion, allogeneic stem cell transplantation represents an effective treatment for the most severely affected MKD patients. However, treatment-related morbidity and mortality are significant. Transplantation may be justified in patients with a severe disease course on conservative therapy.

Molecular Genetics Diversity of Primary Hemophagocytic Lymphohistiocytosis among Polish Pediatric Patients.

Hemophagocytic lymphohistiocytosis (HLH) is a clinical syndrome of life-threatening inflammation caused by an excessive, prolonged and ineffective immune response. An increasing number of HLH cases is recognized in Poland, but the genetic causes of familial HLH (FHL) have not been reported. We investigated the molecular genetics and associated outcomes of pediatric patients who met HLH criteria. We studied 54 patients with HLH, 36 of whom received genetic studies. Twenty-five patients were subjected to direct sequencing of the PRF1, UNC13D, STX11, XIAP and SH2D1A genes. Additionally, 11 patients were subjected to targeted next-generation sequencing. In our study group, 17 patients (31%) were diagnosed with primary HLH, with bi-allelic FHL variants identified in 13 (36%) patients whereas hemizygous changes were identified in 4 patients with X-linked lymphoproliferative diseases. In addition, one patient was diagnosed with X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia due to a hemizygous MAGT1 variant; another newborn was diagnosed with auto-inflammatory syndrome caused by MVK variants. The majority (65%) of FHL patients carried UNC13D pathogenic variants, whereas PRF1 variants occurred in two patients. Novel variants in UNC13D, PRF1 and XIAP were detected. Epstein-Barr virus was the most common trigger noted in 23 (65%) of the patients with secondary HLH. In three patients with secondary HLH, heterozygous variants of FHL genes were found. Overall survival for the entire study group was 74% with a median of 3.6 years of follow-up. Our results highlight the diversity of molecular causes of primary HLH in Poland.

Difficult Balance Between EBV Treatment and Posttransplant Immunosuppression: A Successful Transplant in a Child With Recurrent Epstein-Barr Virus-Induced Hemophagocytic Lymphohistiocytosis.

BACKGROUND: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening clinical syndrome. HLH can be classified into 2 major forms: primary and secondary. Viral infections are frequently implicated in the onset of active HLH episodes. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative treatment for primary HLH and refractory/relapsed HLH after proper chemoimmunotherapy, although following immunosuppressive therapy may lead to infectious complications, including viral infections. CASE PRESENTATION: We report a case of a 6-year-old boy with Epstein-Barr virus (EBV)-induced hemophagocytic lymphohistiocytosis. The patient underwent an allo-HSCT from a 10/10 HLA-matched unrelated donor. Because he received myeloablative and immunosuppressive treatment, another EBV reactivation occurred, as well as cytomegalovirus (CMV) reactivation. After antiviral therapy, on day +27, elimination of EBV and CMV was achieved. Repeated chimerism tests evaluated decreasing donor chimerism; graft-versus-host disease prophylaxis was reduced from day +32 and eventually withdrawn. Later on, the patient developed acute graft-versus-host disease (skin rush, gastrointestinal dysfunction). Immunosuppressive agents (methylprednisolone, cyclosporine) were applied once again, which led to an increase of CMV viremia and polyomavirus (BK virus) primary infection. CONCLUSIONS: Virus infection can induct a severe disorder, such as HLH, and recur after its treatment. We believe our case represents dynamic changes in immunologic reaction to viral infection, which depend on modifications in treatment after allo-HSCT. These observations underscore the importance and difficulty of balancing immunosuppressive therapy and infection control.

Factors Modifying Outcome After MIBG Therapy in Children With Neuroblastoma-A National Retrospective Study.

BACKGROUND: Neuroblastoma is the most common pediatric extracranial tumor with varied prognoses, but the survival of treated refractory or relapsing patients remains poor. OBJECTIVE: This analysis presents the outcomes of children with neuroblastoma undergoing MIBG therapy in Poland in 2006-2019. STUDY DESIGN: A retrospective cohort of 55 patients with refractory or relapsed neuroblastoma treated with I-131 MIBG in Poland in 2006-2019 was analyzed. The endpoints were overall survival (OS), event-free survival (EFS), cumulative incidence (CI) of second cancers and CI of hypothyroidism. Survival curves were estimated using the Kaplan-Meier method and compared between the cohorts by the log-rank test. Cox modeling was adopted to estimate hazard ratios for OS and EFS, considering factors with P < 0.2. RESULTS: Fifty-five patients with a median age of 78.4 months (range 18-193) with neuroblastoma underwent one or more (4 patients) courses of MIBG I-131 therapy. Fifteen patients were not administered chemotherapy, 3 children received standard-dose chemotherapy, and 37 patients were administered high-dose chemotherapy (HDCT) (busulfan-melphalan in 24 and treosulfan-based in 12 patients). Forty-six patients underwent stem cell transplantation, with autologous (35 patients), haploidentical (6), allogeneic (4), and syngeneic grafts (1). The median time from first MIBG therapy to SCT was 22 days. Children with relapsing tumors had inferior OS compared to those with primary resistant disease (21.2% vs 58.7%, p=0.0045). Survival was better in patients without MYCN gene amplification. MIBG therapy was never curative, except in patients further treated with HDCT with stem cell rescue irrespective of the donor type. 31 patients were referred for immune therapy after MIBG therapy, and the 5-year OS in this group was superior to the untreated children (55.2% vs 32.7%, p=0.003), but the difference in the 5-year EFS was not significant (25.6% vs 32.9%, p=ns). In 3 patients, a second malignancy was diagnosed. In 19.6% of treated children, hypothyroidism was diagnosed within 5 years after MIBG therapy. CONCLUSION: MIBG therapy can be incorporated into the therapeutic strategy of relapsed or resistant neuroblastoma patients as preconditioning with HDCT rather than stand-alone therapy. Follow-up is required due to the incidence of thyroid failure and risk of second cancers.

Expanded circulating hematopoietic stem/progenitor cells as novel cell source for the treatment of TCIRG1 osteopetrosis.

Allogeneic hematopoietic stem cell transplantation is the treatment of choice for autosomal recessive osteopetrosis caused by defects in the TCIRG1 gene. Despite recent progress in conditioning, a relevant number of patients are not eligible for allogeneic stem cell transplantation because of the severity of the disease and significant transplant-related morbidity. We exploited peripheral CD34+ cells, known to circulate at high frequency in the peripheral blood of TCIRG1-deficient patients, as a novel cell source for autologous transplantation of gene corrected cells. Detailed phenotypical analysis showed that circulating CD34+ cells have a cellular composition that resembles bone marrow, supporting their use in gene therapy protocols. Transcriptomic profile revealed enrichment in genes expressed by hematopoietic stem and progenitor cells (HSPCs). To overcome the limit of bone marrow harvest/ HSPC mobilization and serial blood drawings in TCIRG1 patients, we applied UM171-based ex-vivo expansion of HSPCs coupled with lentiviral gene transfer. Circulating CD34+ cells from TCIRG1-defective patients were transduced with a clinically-optimized lentiviral vector (LV) expressing TCIRG1 under the control of phosphoglycerate promoter and expanded ex vivo. Expanded cells maintained long-term engraftment capacity and multi-lineage repopulating potential when transplanted in vivo both in primary and secondary NSG recipients. Moreover, when CD34+ cells were differentiated in vitro, genetically corrected osteoclasts resorbed the bone efficiently. Overall, we provide evidence that expansion of circulating HSPCs coupled to gene therapy can overcome the limit of stem cell harvest in osteopetrotic patients, thus opening the way to future gene-based treatment of skeletal diseases caused by bone marrow fibrosis.

Hematopoietic Stem Cell Transplantation Positively Affects the Natural History of Cancer in Nijmegen Breakage Syndrome.

PURPOSE: Nijmegen breakage syndrome (NBS) is a DNA repair disorder with a high predisposition to hematologic malignancies. EXPERIMENTAL DESIGN: We describe the natural history of NBS, including cancer incidence, risk of death, and the potential effectiveness of hematopoietic stem cell transplantation (HSCT) in preventing both pathologies: malignancy and immunodeficiency. RESULTS: Among 241 patients with NBS enrolled in the study from 11 countries, 151 (63.0%) patients were diagnosed with cancer. Incidence rates for primary and secondary cancer, tumor characteristics, and risk factors affecting overall survival (OS) were estimated. The cumulative cancer incidence was 40.21% ± 3.5% and 77.78% ± 3.4% at 10 years and 20 years of follow-up, respectively. Most of the tumors n = 95 (62.9%) were non-Hodgkin lymphomas. Overall, 20 (13.2%) secondary malignancies occurred at a median age of 18 (interquartile range, 13.7-21.5) years. The probability of 20-year overall survival (OS) for the whole cohort was 44.6% ± 4.5%. Patients who developed cancer had a shorter 20-year OS than those without malignancy (29.6% vs. 86.2%; P < 10-5). A total of 49 patients with NBS underwent HSCT, including 14 patients transplanted before malignancy. Patients with NBS with diagnosed cancer who received HSCT had higher 20-year OS than those who did not (42.7% vs. 30.3%; P = 0.038, respectively). In the group of patients who underwent preemptive transplantation, only 1 patient developed cancer, which is 6.7 times lower as compared with nontransplanted patients [incidence rate ratio 0.149 (95% confidence interval, 0.138-0.162); P < 0.0001]. CONCLUSIONS: There is a beneficial effect of HSCT on the long-term survival of patients with NBS transplanted in their first complete remission of cancer.

Diagnostic difficulties of AH1N1 influenza infection in children with acute lymphoblastic leukemia: Two case reports.

INTRODUCTION: Children with acute lymphoblastic leukemia (ALL) are at a risk of developing influenza-related complications. Approximately 10% of influenza-infected children with ALL or other types of cancer need intensive care, and 5% of them eventually die. PATIENTS' CONCERNS: We report 2 children with ALL and the swine-origin influenza A virus infection. Diagnosing influenza in them was a challenge. Medical records of these children were reviewed for demographic, clinical, and laboratory data. Patients were hospitalized in the Department of Pediatric Hematology, Oncology, and Transplantology of the Medical University of Lublin, Poland. Case 1 involved a 2-year-old girl who, according to acute lymphoblastic leukemia intercontinental Berlin-Frankfürt-Münster protocol 2009, started chemotherapy in July 2015. She was categorized in the intermediate risk group and received the induction and consolidation phase of the therapy without severe complications. The reinduction therapy was administered in the outpatient department till the 15 day. On the 20 day of this phase, she was admitted to our department with fever, mucositis, tachypnea, abdominal pain, and diarrhea. In September 2009, a 14-year-old boy (case 2) who, according to acute lymphoblastic leukemia intercontinental Berlin-Frankfürt-Münster protocol 2002, was categorized in the high-risk (HR) group, received the induction (Protocol I) phase of therapy without severe complications. On the 7 day of the HR-1 course, he manifested fever and strong, tiring cough, followed by strong mucositis. Chemotherapy had to be interrupted in both children. DIAGNOSIS: Respiratory viral infections, causing pneumonia, occurred in both patients during anticancer treatment. Initially, the real-time polymerase chain reaction test for the swine-origin influenza A was negative in both patients, which delayed the diagnosis. Additionally, bacterial, and fungal complications were also observed. INTERVENTIONS: Both patients received oseltamivir twice a day, a broad-spectrum antibiotic, antifungal drug, and granulocyte colony growth factor. OUTCOMES: The disease progressed quickly, and our patients subsequently died. CONCLUSION: We speculated that early antiviral treatment can help in the better management of patients in the HR group. It is also important to minimize influenza morbidity and mortality by vaccinating family members, using empiric therapy, providing immediate antiviral therapy, and educating parents about hygiene measures.

Clinical characteristics and outcome of pediatric patients diagnosed with Langerhans cell histiocytosis in pediatric hematology and oncology centers in Poland.

BACKGROUND: Langerhans cell histiocytosis (LCH) affects 1-2 in 1,000,000 people. The disease is not associated with increased risk of treatment failure (especially among older children), but appropriate procedures implemented in advance can eliminate complications which might appear and significantly worsen the patients' quality of life. Thus, we sought to evaluate the clinical features, management, and outcome of children with LCH treated in Polish pediatric hematology-oncology centers. MATERIALS AND METHODS: One hundred eighty two patients with LCH were treated according to the Histiocytic Society Guidelines between 2010 and 2017. The participating centers were requested to provide the following data: demographic, clinical, as well as local or systemic treatment data and patients' outcome. Overall survival (OS) and event free survival (EFS) were estimated by Kaplan-Meier methods and compared using the log-rank test. RESULTS: Sixty nine percent of children were classified as single system (SS). The patients with SS disease were significantly older as compared to the children with multisystem disease (MS), 6 vs. 2.3 years respectively (p 0.003). Bones were involved in 76% of patients. Systemic treatment was applied to 47% of children with SS disease and 98% with MS disease. Fourteen patients relapsed while two children died. OS and EFS in entire group were 0.99 and 0.91 respectively (with median follow-up 4.3 years). CONCLUSION: The treatment of LCH in Polish centers was effective, however, new approaches, including mutation analyses and good inter-center cooperation, are needed to identify patients who might require modification or intensification of treatment.

The Clinical and Genetic Spectrum of 82 Patients With RAG Deficiency Including a c.256_257delAA Founder Variant in Slavic Countries.

Background: Variants in recombination-activating genes (RAG) are common genetic causes of autosomal recessive forms of combined immunodeficiencies (CID) ranging from severe combined immunodeficiency (SCID), Omenn syndrome (OS), leaky SCID, and CID with granulomas and/or autoimmunity (CID-G/AI), and even milder presentation with antibody deficiency. Objective: We aim to estimate the incidence, clinical presentation, genetic variability, and treatment outcome with geographic distribution of patients with the RAG defects in populations inhabiting South, West, and East Slavic countries. Methods: Demographic, clinical, and laboratory data were collected from RAG-deficient patients of Slavic origin via chart review, retrospectively. Recombinase activity was determined in vitro by flow cytometry-based assay. Results: Based on the clinical and immunologic phenotype, our cohort of 82 patients from 68 families represented a wide spectrum of RAG deficiencies, including SCID (n = 20), OS (n = 37), and LS/CID (n = 25) phenotypes. Sixty-seven (81.7%) patients carried RAG1 and 15 patients (18.3%) carried RAG2 biallelic variants. We estimate that the minimal annual incidence of RAG deficiency in Slavic countries varies between 1 in 180,000 and 1 in 300,000 live births, and it may vary secondary to health care disparities in these regions. In our cohort, 70% (n = 47) of patients with RAG1 variants carried p.K86Vfs*33 (c.256_257delAA) allele, either in homozygous (n = 18, 27%) or in compound heterozygous (n = 29, 43%) form. The majority (77%) of patients with homozygous RAG1 p.K86Vfs*33 variant originated from Vistula watershed area in Central and Eastern Poland, and compound heterozygote cases were distributed among all Slavic countries except Bulgaria. Clinical and immunological presentation of homozygous RAG1 p.K86Vfs*33 cases was highly diverse (SCID, OS, and AS/CID) suggestive of strong influence of additional genetic and/or epigenetic factors in shaping the final phenotype. Conclusion: We propose that RAG1 p.K86Vfs*33 is a founder variant originating from the Vistula watershed region in Poland, which may explain a high proportion of homozygous cases from Central and Eastern Poland and the presence of the variant in all Slavs. Our studies in this cohort of RAG1 founder variants confirm that clinical and immunological phenotypes only partially depend on the underlying genetic defect. As access to HSCT is improving among RAG-deficient patients in Eastern Europe, we anticipate improvements in survival.

Treosulfan-fludarabine-thiotepa-based conditioning treatment before allogeneic hematopoietic stem cell transplantation for pediatric patients with hematological malignancies.

Treosulfan-based conditioning prior to allogeneic transplantation has been shown to have myeloablative, immunosuppressive, and antineoplastic effects associated with reduced non-relapse mortality (NRM) in adults. Therefore, we prospectively evaluated the safety and efficacy of treosulfan-based conditioning in children with hematological malignancies in this phase II trial. Overall, 65 children with acute lymphoblastic leukemia (35.4%), acute myeloid leukemia (44.6%), myelodysplastic syndrome (15.4%), or juvenile myelomonocytic leukemia (4.6%) received treosulfan intravenously at a dose of 10 mg/m2/day (7.7%), 12 g/m2/day (35.4%), or 14 g/m2/day (56.9%) according to their individual body surface area in combination with fludarabine and thiotepa. The incidence of complete donor chimerism at day +28 was 98.4% with no primary and only one secondary graft failure. At 36 months, NRM was only 3.1%, while relapse incidence was 21.7%, and overall survival was 83.0%. The cumulative incidence of acute graft-vs.-host disease was 45.3% for grades I-IV and 26.6% for grades II-IV. At 36 months, 25.8% overall and 19.4% moderate/severe chronic graft-vs.-host disease were reported. These data confirm the safe and effective use of treosulfan-based conditioning in pediatric patients with hematological malignancies. Therefore, treosulfan/fludarabine/thiotepa can be recommended for myeloablative conditioning in children with hematological malignancies.