Advances in the First Line Treatment of Pediatric Acute Myeloid Leukemia in the Polish Pediatric Leukemia and Lymphoma Study Group from 1983 to 2019

Analysis of early and treatment related deaths among children and adolescents with acute myeloid leukemia in Poland: 2005-2023

Background

A personalised approach to the treatment of acute myeloid leukemia (AML) in children and adolescents, as well as the development of supportive therapies, has significantly improved survival. Despite this, some patients still die before starting treatment or in an early phase of therapy before achieving remission. The study analysed the frequency, clinical features and risk factors for early deaths (ED) and treatment related deaths (TRD) of children and adolescents with AML.

Methods

From January 2005 to November 2023, 646 children with AML treated in the centers of the Polish Pediatric Leukemia and Lymphoma Study Group according to three subsequent therapeutic protocols were evaluated: AML-BFM 2004 Interim (385 children), AML-BFM 2012 Registry (131 children) and AML-BFM 2019 (130 children).

Results

Out of 646 children, early death occurred in 30 children, including 15 girls. The median age was 10.7 years (1 day to 18 years). More than half of the patients (53%) were diagnosed with acute myelomonocytic leukemia (M5) and 13% with acute promyelocytic leukemia (M3). The ED rate for the three consecutive AML-BFM protocols was 4.9% vs. 5.3% vs. 3.1%, respectively. In 19 patients, death occurred before the 15th day of treatment, in 11 between the 15th and 42nd day. The most common cause of death before the 15th day (ED15) was leukostasis and bleeding, whereas between the 15th and 42nd day (ED15-42), infections, mainly bacterial sepsis. A significant association was found between ED15 and high leukocyte count (>10 × 109/L), M3 leukemia (p < 0.001), and ED15-42 and age <1 year (p = 0.029). In the univariate analysis only initial high leukocyte count >100 × 109/L, was a significant predictor of early death. The overall TRD for the entire study period was 3.4%. The main cause of death were infections, mainly bacterial sepsis (10 children out of 22, 45.4%).

Conclusions

Hyperleukocytosis remains significant factor of early mortality in patients with AML, despite the introduction of various cytoreductive methods. Infections are still the main cause of treatment related deaths. A more individualized approach by using new targeted drugs may be the therapeutic option of choice in the future.

Gemtuzumab ozogamicin for relapsed or primary refractory acute myeloid leukemia in children-the Polish Pediatric Leukemia and Lymphoma Study Group experience

Background

Gemtuzumab ozogamicin (GO), one of the first targeted drugs used in oncology, consists of an anti-cluster of differentiation 33 (CD33) monoclonal antibody bound to a derivative of cytotoxic calicheamicin. After the drug withdrawn in 2010 due to a significantly higher rate of early deaths, GO regained approval in 2017 for the treatment of newly diagnosed, refractory, or relapsed acute myeloid leukemia (AML) in adults and children over 15 years of age. The objective of the study was a retrospective analysis of clinical characteristics, treatment outcomes, and GO toxicity profile in children with primary refractory or relapsed (R/R) AML treated in Poland from 2008 to 2022.

Methods

Data were collected through the Polish Registry of Acute Myeloid Leukemia. From January 2008 to December 2022, 35 children with R/R AML were treated with GO in seven centers of the Polish Pediatric Leukemia and Lymphoma Study Group.

Results

Most of the children (30 of 35) received only one GO cycle in combination with various chemotherapy cycles (IDA-FLA, DOXO-FLA, FLA, FLAG, and others). Eighteen children (51%) achieved complete remission (CR), 14 did not respond to treatment, and three progressed. GO therapy was followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 18 children in CR. The 5-year overall survival (OS) after GO therapy was 37.1% ± 8.7% for the total cohort. There was a trend toward a superior outcome in patients with strong expression of CD33 expression (over 50% positive cells) compared with that in patients with lower expression of CD33 (OS, 41.2% ± 11.9% versus 27.8% ± 13.2%; p = 0.5; 5-year event-free survival, 35.4% ± 11.6% versus 25.7% ± 12.3%; p = 0.5, respectively). Children under 15 years have better outcome (OS, 34.9% ± 10.4% versus 30% ± 14.5%, p = 0.3). The most common adverse events were bone marrow aplasia, fever of unknown origin, infections, and elevated liver enzyme elevation. Sinusoidal obstruction syndrome occurred in two children.

Conclusions

The use of GO in severely pretreated children, including those under 15 years of age, with previous failure of AML treatment is a feasible and effective bridging therapy to allo-HSCT with an acceptable toxicity profile.

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.

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.

Molecular-Targeted Therapy of Pediatric Acute Myeloid Leukemia

Acute myeloid leukemia (AML) accounts for approximately 15–20% of all childhood leukemia cases. The overall survival of children with acute myeloid leukemia does not exceed 82%, and the 5-year event-free survival rates range from 46% to 69%. Such suboptimal outcomes are the result of numerous mutations and epigenetic changes occurring in this disease that adversely affect the susceptibility to treatment and relapse rate. We describe various molecular-targeted therapies that have been developed in recent years to meet these challenges and were or are currently being studied in clinical trials. First introduced in adult AML, novel forms of treatment are slowly beginning to change the therapeutic approach to pediatric AML. Despite promising results of clinical trials investigating new drugs, further clinical studies involving greater numbers of pediatric patients are still needed to improve the outcomes in childhood AML.

Pediatric Acute Myeloid Leukemia—Past, Present, and Future

This review reports about the main steps of development in pediatric acute myeloid leukemia (AML) concerning diagnostics, treatment, risk groups, and outcomes. Finally, a short overview of present and future approaches is given.

Blinatumomab as a Bridge Therapy for Hematopoietic Stem Cell Transplantation in Pediatric Refractory/Relapsed Acute Lymphoblastic Leukemia

Simple Summary

Immunotherapies are modern treatment modalities, giving hope for improvements of frozen cure rates in many childhood malignancies. More intensive cytotoxic chemotherapy cycles didn’t improve cure rates, only increase number of adverse events. Blinatumomab, a bispecific CD3/CD19 antibody construct, has been successfully used in relapsed/refractory r/r B-cell precursor ALL (BCP-ALL) as a bridge to hematopoietic stem cell transplantation (HSCT). We retrospectively assessed the efficacy and toxicity of blinatumomab in 13 children with r/r BCP-ALL. The response rate in our cohort of patients was 85%, with subsequent feasible HSCT in 11 out of 13 children. Although our study had some limitations with regard to its retrospective design and limited patient population, it clearly showed blinatumomab as not only a feasible but also an effective therapeutic option in pretreated children with r/r BCP-ALL, with a tolerable toxicity profile, paving the way for an HSCT procedure. To date, this is the first retrospective study from Poland on efficacy and toxicity of blinatumomab therapy in children with r/r ALL.

Abstract

Despite the progress that has been made in recent decades in the treatment of pediatric acute leukemias, e.g., converting acute lymphoblastic leukemia (ALL) from a fatal to a highly curable disease, 15–20% of children still relapse. Blinatumomab, a bispecific CD3/CD19 antibody construct, has been successfully used in relapsed/refractory r/r B-cell precursor ALL (BCP-ALL) as a bridge to hematopoietic stem cell transplantation (HSCT). We retrospectively assessed the efficacy and toxicity of blinatumomab in 13 children with r/r BCP-ALL. Between 2017 and 2021, thirteen children, aged 1–18 years, with r/r BCP-ALL were treated with blinatumomab. Two patients were administered blinatumomab for refractory relapse without complete remission (CR), one due to primary refractory disease, and ten patients were in CR with minimal residual disease (MRD) ≥ 10⁻³. The response rate in our cohort of patients was 85%, with subsequent feasible HSCT in 11 out of 13 children. Ten children reached MRD negativity after the first blinatumomab administration. The three-year OS for the study patients was 85% (Mantel–Cox, p < 0.001) and median follow-up was 24.5 (range: 1–47). All responders proceeded to HSCT and are alive in CR, and MRD negative. Although our study had some limitations with regard to its retrospective design and limited patient population, it clearly showed blinatumomab as not only a feasible but also an effective therapeutic option in pretreated children with r/r BCP-ALL, with a tolerable toxicity profile, paving the way for an HSCT procedure.

Analysis of Peripheral Blood Mononuclear Cells Gene Expression Highlights the Role of Extracellular Vesicles in the Immune Response following Hematopoietic Stem Cell Transplantation in Children

Hematopoietic stem cell transplantation (HSCT) is an effective treatment method used in many neoplastic and non-neoplastic diseases that affect the bone marrow, blood cells, and immune system. The procedure is associated with a risk of adverse events, mostly related to the immune response after transplantation. The aim of our research was to identify genes, processes and cellular entities involved in the variety of changes occurring after allogeneic HSCT in children by performing a whole genome expression assessment together with pathway enrichment analysis. We conducted a prospective study of 27 patients (aged 1.5–18 years) qualified for allogenic HSCT. Blood samples were obtained before HSCT and 6 months after the procedure. Microarrays were used to analyze gene expressions in peripheral blood mononuclear cells. This was followed by Gene Ontology (GO) functional enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and protein–protein interaction (PPI) analysis using bioinformatic tools. We found 139 differentially expressed genes (DEGs) of which 91 were upregulated and 48 were downregulated. “Blood microparticle”, “extracellular exosome”, “B-cell receptor signaling pathway”, “complement activation” and “antigen binding” were among GO terms found to be significantly enriched. The PPI analysis identified 16 hub genes. Our results provide insight into a broad spectrum of epigenetic changes that occur after HSCT. In particular, they further highlight the importance of extracellular vesicles (exosomes and microparticles) in the post-HSCT immune response.

Concentrations of Insulin-like Growth Factors and Insulin-like Growth Factor-Binding Proteins and Respective Gene Expressions in Children before and after Hematopoietic Stem Cell Transplantation

Insulin-like growth factors (IGF-1 and IGF-2) and insulin-like growth factor-binding proteins (IGFBP-1 to -7) are involved in the regulation of cell proliferation and differentiation and may be associated with various metabolic parameters. The aim of our study was to compare levels of IGFs and IGFBPs and the expressions of their genes in children before and after hematopoietic stem cell transplantation (HSCT) to assess their potential as markers of late metabolic complications of HSCT. We also conducted additional comparisons with healthy controls and of correlations of IGF and IGFBP levels with anthropometric and biochemical parameters. We analyzed 19 children treated with HSCT and 21 healthy controls. We found no significant differences in the levels of IGFs and IGFBPs and expressions of their genes before and after HSCT, while IGF and IGFBP levels were significantly lower in children treated with HSCT compared with controls. We conclude that our results did not reveal significant differences between the levels of IGFs and IGFBPs before and after HSCT, which would make them obvious candidates for markers of late complications of the procedure in children. However, due to the very low number of patients this conclusion must be taken with caution and may be altered by further research.