Overview of therapy and strategies for optimizing outcomes in de novo pediatric acute myeloid leukemia

Pediatric acute myeloid leukemia and hyperleukocytosis with WBC count greater than 50 × 109/L

BACKGROUND

Acute myeloid leukemia (AML) and hyperleukocytosis have an unfavorable prognosis, but the impact of hyperleukocytosis on the prognosis of pediatric AML remains uncertain. We investigated the clinical characteristics and prognosis of pediatric AML with hyperleukocytosis, defined as WBC ≥ 50 × 109/L.

METHODS

A total of 132 patients with newly diagnosed childhood AML with hyperleukocytosis were consecutively enrolled at our center from September 2009 to August 2021 to investigate prognostic factors and clinical outcomes.

RESULTS

Hyperleukocytosis occurred in 27.4% of AML patients. Pediatric patients with hyperleukocytosis had similar CR and OS rates to those without hyperleukocytosis, but had a lower EFS rate. In our study, rates of CR1, mortality, relapsed/refractory disease, and HSCT were comparable between AML patients with WBC counts of 50-100 × 109/L and ≥ 100 × 109/L. AML patients with a WBC count of 50-100 × 109/L had a similar 5-year OS rate to patients with a WBC count ≥ 100 × 109/L (74.6% vs. 75.4%, P = 0.921). Among all patients with hyperleukocytosis, the FAB M5 subtype was associated with significantly inferior survival, and the prognosis of CBF-AML was good.

CONCLUSIONS

Pediatric AML patients with hyperleukocytosis have the similar prognosis regardless of whether their WBC count is 50-100 × 109/L or ≥ 100 × 109/L.

Cytarabine dose reduction in patients with low-risk acute myeloid leukemia: A report from the Children's Oncology Group

BACKGROUND

The optimal number of chemotherapy courses for low-risk (LR) pediatric acute myeloid leukemia (AML) is not known.

OBJECTIVE

To compare outcomes for four (21.6 g/m² cytarabine) versus five (45.6 g/m² cytarabine) chemotherapy courses for LR-AML using data from Children's Oncology Group (COG) AAML0531 and AAML1031.

METHODS

We compared relapse risk (RR), disease-free survival (DFS), and overall survival (OS), and the differential impact in LR subgroups for patients receiving four versus five chemotherapy courses. Cox (OS and DFS) and risk (RR) regressions were used to estimate hazard ratios (HR) to compare outcomes.

RESULTS

A total of 923 LR-AML patients were included; 21% received five courses. Overall, LR-AML patients who received four courses had higher RR (40.9% vs. 31.4%; HR = 1.40, 95% confidence interval [CI]: 1.06-1.85), and worse DFS (56.0% vs. 67.0%; HR = 1.45, 95% CI: 1.10-1.91). There was a similar decrement in OS though it was not statistically significant (77.0% vs. 83.5%; HR = 1.45, 95% CI: 0.97-2.17). Stratified analyses revealed the detrimental effects of cytarabine dose de-escalation to be most pronounced in the LR-AML subgroup with uninformative cytogenetic/molecular features who were minimal residual disease (MRD) negative after the first induction course (EOI1). The absolute decrease in DFS with four courses for patients with favorable cytogenetic/molecular features and positive MRD was similar to that observed for patients with uninformative cytogenetic/molecular features and negative MRD at EOI1, though not statistically significant.

CONCLUSIONS

Our results support de-escalation of cytarabine exposure through the elimination of a fifth chemotherapy course only for LR-AML patients who have both favorable cytogenetic/molecular features and negative MRD after the first induction cycle.

Predictive impact of residual disease detected using multiparametric flow cytometry on risk stratification of paediatric acute myeloid leukaemia with normal karyotype

INTRODUCTION

Residual disease (RD) detected using multiparametric flow cytometry (MFC) is an independent predictive variable of relapse in acute myeloid leukaemia (AML). However, RD thresholds and optimal assessment time points remain to be validated.

MATERIAL AND METHODS

We investigated the significance of RD after induction therapy in paediatric AML with normal karyotype between June 2008 and June 2018. Bone marrow samples from 73 patients were collected at the end of the first (BMA-1) and second (BMA-2) induction courses to monitor RD using MFC.

RESULTS

Presence of RD after BMA-1 and/or BMA-2 correlated with poor relapse-free (RFS) and overall survival at 0.1% RD cutoff level. Receiver operating characteristic curve showed that RD cutoff levels of 1.3% and 0.5% after BMA-1 and BMA-2, respectively, predicted events with the highest sensitivity and specificity. In multivariable analysis, RD after BMA-2 was the strongest independent risk predictor for poor RFS (hazard ratio 2.934; 95% confidence interval: 1.106-7.782; P = .031).

CONCLUSIONS

Our study therefore suggests that an RD level ≥0.5% after BMA-2 has a significant predictive impact on the prognosis of AML patients having normal karyotype and thus guide the stratification of treatment strategies.

Lymphoid markers predict prognosis of pediatric and adolescent acute myeloid leukemia

Acute Myeloid Leukemia (AML) is a complex and highly aggressive disease. To characterize the prognostic factors of pediatric patients with AML relapse, a retrospective cohort study was performed to collect data from children and adolescents, at a hematological oncology reference center, over 11 years. We selected 51 cases of the disease, diagnosed and treated uniformly, divided into two groups: with complete remission (n = 33; 65 %) and with relapse (n = 18; 35 %). The groups were homogeneous concerning demographic characteristics and hematological parameters at diagnosis. AML M3 was the most common subtype (n = 19; 37 %) and was associated with a good prognosis. The highest rate of relapse was with AML M0 (n = 3 of 5 patients; 60 %). The most predominant gene mutation, FLT3-ITD, did not influence the prognosis in our study. The complete remission group presented a higher mean frequency of positive cells for the granulocytic marker CD13a at diagnosis. In cases with AML relapse, CD36, CD4, CD7, and CD22 were the most expressed markers. Increase incidence of recurrence was associated with CD7 (HR 1.035; p = 0.003), CD4 (HR 1.032, p = 0.001) and CD22 (HR 1.042; p = 0.049). Our results highlight the importance of analyzing immunophenotypic markers to help predict the outcome of AML in children and adolescents.

Expanded activated autologous lymphocyte infusions improve outcomes of low- and intermediate-risk childhood acute myeloid leukemia with low level of minimal residual disease

The presence of minimal residual disease (MRD) is a risk factor for relapse among children with acute myeloid leukemia (AML), and eliminating MRD can usually improve survival rates. To investigate the effect of expanded activated autologous lymphocytes (EAALs) combined with chemotherapy on eliminating MRD and improving survival rates of children with AML, we retrospectively analyzed the results of 115 children with low- or intermediate-risk AML with MRD treated at the Pediatric Hematological Center, Peking University People's Hospital, between January 2010 and January 2016. The patients were assigned to the chemotherapy plus EAAL (combined therapy) group (n = 61) and chemotherapy group (n = 54). The MRD-negativity rates were 95.1% (58/61) in the combined therapy group and 63.0% (34/54) in the chemotherapy group (P < 0.0001) during consolidation treatment. The 5-year event-free survival rate was higher in the combined therapy group than in the chemotherapy group (86.3 ± 4.6% vs. 72.1 ± 6.1%, P = 0.025). No severe adverse event was observed after EAAL infusion. The present study showed that EAAL combined with chemotherapy could improve the MRD-negativity rate and event-free survival rate among children with AML with low level MRD-positive status.

Prognostic Impact of Extramedullary Infiltration in Pediatric Low-risk Acute Myeloid Leukemia: A Retrospective Single-center Study Over 10 Years

BACKGROUND

The impact of extramedullary infiltration (EMI) on the clinical outcomes of pediatric patients with acute myeloid leukemia (AML) are controversial.

PATIENTS AND METHODS

A total of 214 pediatric patients with low-risk AML were classified as having EMI (central nervous leukemia [CNSL] and/or myeloid sarcoma [MS]) and not having EMI. Patients with isolated MS before AML diagnosis by bone marrow examination were confirmed with histopathologic examination. For patients diagnosed with AML by bone marrow examination, a thorough physical examination and radiologic imaging were used to confirm MS.

RESULTS

Male gender, a high white blood cell count, the FAB-M5 subtype, t(8;21) and t(1;11) abnormalities, and c-KIT mutations were associated with EMI. The presence of MS was associated with a low complete remission rate (63.6% vs. 79.4%; P = .000) and poor 3-year relapse-free survival (RFS) (62.6% ± 7.5% vs. 87.0% ± 2.8%; P = .000) and 3-year overall survival (73.5% ± 7% vs. 88.8% ± 2.6%; P = .011). Multivariate analysis revealed that MS was a poor prognostic factor for RFS and overall survival. Bone infiltration was an independent risk factor for inferior RFS with MS. Patients with CNSL had a low complete remission rate (58.3% vs. 77.2%; P = .045); however, CNSL did not significantly affect the survival of low-risk patients with AML.

CONCLUSION

MS should be considered an independent risk factor to guide stratified treatment.

Effect of Dexrazoxane on Left Ventricular Systolic Function and Treatment Outcomes in Patients With Acute Myeloid Leukemia: A Report From the Children's Oncology Group

PURPOSE

To determine whether dexrazoxane provides effective cardioprotection during frontline treatment of pediatric acute myeloid leukemia (AML) without increasing relapse risk or noncardiac toxicities of the chemotherapy regimens.

PATIENTS AND METHODS

This was a multicenter study of all pediatric patients with AML without high allelic ratio FLT3/ITD treated in the Children's Oncology Group trial AAML1031 between 2011 and 2016. Median follow-up was 3.5 years. Dexrazoxane was administered at the discretion of treating physicians and documented at each course. Ejection fraction (EF) and shortening fraction (SF) were recorded after each course and at regular intervals in follow-up. Per protocol, anthracyclines were to be withheld if there was evidence of left ventricular systolic dysfunction (LVSD) defined as SF < 28% or EF < 55%. Occurrence of LVSD, trends in EF and SF, 5-year event-free survival (EFS) and overall survival (OS), and treatment-related mortality (TRM) were compared by dexrazoxane exposure.

RESULTS

A total of 1,014 patients were included in the analyses; 96 were exposed to dexrazoxane at every anthracycline course, and 918 were never exposed. Distributions of sex, age, race, presenting WBC count, risk group, treatment arm, and compliance with cardiac monitoring were similar for dexrazoxane-exposed and -unexposed patients. Dexrazoxane-exposed patients had significantly smaller EF and SF declines than unexposed patients across courses and a lower risk for LVSD (26.5% v 42.2%; hazard ratio, 0.55; 95% CI, 0.36 to 0.86; P = .009). Dexrazoxane-exposed patients had similar 5-year EFS (49.0% v 45.1%; P = .534) and OS (65.0% v 61.9%; P = .613) to those unexposed; however, there was a suggestion of lower TRM with dexrazoxane (5.7% v 12.7%; P = .068).

CONCLUSION

Dexrazoxane preserved cardiac function without compromising EFS and OS or increasing noncardiac toxicities. Dexrazoxane should be considered for cardioprotection during frontline treatment of pediatric AML.

Discovery of orally active indirubin-3'-oxime derivatives as potent type 1 FLT3 inhibitors for acute myeloid leukemia

FMS-like receptor tyrosine kinase-3 (FLT3) is expressed on acute leukemia cells and is implicated in the survival, proliferation and differentiation of hematopoietic cells in most acute myeloid leukemia (AML) patients. Despite recent achievements in the development of FLT3-targeted small-molecule drugs, there are still unmet medical needs related to kinase selectivity and the progression of some mutant forms of FLT3. Herein, we describe the discovery of novel orally available type 1 FLT3 inhibitors from structure-activity relationship (SAR) studies for the optimization of indirubin derivatives with biological and pharmacokinetic profiles as potential therapeutic agents for AML. The SAR exploration provided important structural insights into the key substituents for potent inhibitory activities of FLT3 and in MV4-11 cells. The profile of the most optimized inhibitor (36) showed IC₅₀ values of 0.87 and 0.32 nM against FLT3 and FLT3/D835Y, respectively, along with potent inhibition against MV4-11 and FLT3/D835Y expressed MOLM14 cells with a GI₅₀ value of 1.0 and 1.87 nM, respectively. With the high oral bioavailability of 42.6%, compound 36 displayed significant in vivo antitumor activity by oral administration of 20 mg/kg once daily dosing schedule for 21 days in a mouse xenograft model. The molecular docking study of 36 in the homology model of the DFG-in conformation of FLT3 resulted in a reasonable binding mode in type 1 kinases similar to the reported type 1 FLT3 inhibitors Crenolanib and Gilteritinib.

Distinct roles of mesenchymal stem and progenitor cells during the development of acute myeloid leukemia in mice

Despite increasing evidence for the involvement of bone marrow (BM) hematopoietic stem cell niche in leukemogenesis, how BM mesenchymal stem and progenitor cells (MSPCs) contribute to leukemia niche formation and progression remains unclear. Using an MLL-AF9 acute myeloid leukemia (AML) mouse model, we demonstrate dynamic alterations of BM cellular niche components, including MSPCs and endothelial cells during AML development and its association with AML engraftment. Primary patient AML cells also induced similar niche alterations in xenografted mice. AML cell infiltration in BM causes an expansion of early B-cell factor 2⁺ (Ebf2⁺) MSPCs with reduced Cxcl12 expression and enhanced generation of more differentiated mesenchymal progenitor cells. Importantly, in vivo fate-mapping indicates that Ebf2⁺ MSPCs participated in AML niche formation. Ebf2⁺ cell deletion accelerated the AML development. These data suggest that native BM MSPCs may suppress AML. However, they can be remodeled by AML cells to form leukemic niche that might contribute to AML progression. AML induced dysregulation of hematopoietic niche factors like Angptl1, Cxcl12, Kitl, Il6, Nov, and Spp1 in AML BM MSPCs, which was associated with AML engraftment and partially appeared before the massive expansion of AML cells, indicating the possible involvement of the niche factors in AML progression. Our study demonstrates distinct dynamic features and roles of BM MSPCs during AML development.

Lnc-SOX6-1 upregulation correlates with poor risk stratification and worse treatment outcomes, and promotes cell proliferation while inhibits apoptosis in pediatric acute myeloid leukemia

INTRODUCTION

To investigate the correlation of long noncoding RNA-SOX6-1 (lnc-SOX6-1) with clinicopathological features and treatment outcomes in pediatric acute myeloid leukemia (AML) patients, and further explore its function in AML cell proliferation and apoptosis.

METHODS

A total of 146 de novo pediatric AML patients and 73 nonhematologic malignancy patients/donors were recruited. Bone marrow samples were obtained, followed by measurement of lnc-SOX6-1 expression by qPCR. Besides, lnc-SOX6-1 expression in various AML cells and control cells was detected. Blank overexpression (NC (+)), lnc-SOX6-1 overexpression (Lnc RNA (+)), blank shRNA (NC (-)), and lnc-SOX6-1 shRNA plasmids (Lnc RNA (-)) were transferred into KG-1 cells and THP-1 cells. Cell proliferation rate and cell apoptosis rate were detected by CCK-8 assay and AV/PI assay, respectively.

RESULTS

Lnc-SOX6-1 expression was upregulated in pediatric AML patients compared to controls, and its high expression correlated with the presence of monosomal karyotype, severer risk stratification, lower possibility of complete response achievement, shorter event-free survival, and poor overall survival. Furthermore, lnc-SOX6-1 expression was elevated in various AML cells compared to normal cells. In KG-1 cells and THP-1 cells, cell proliferation rate was elevated in Lnc RNA (+) group but reduced in Lnc RNA (-) group at 48 and 72 hours, and cell apoptosis rate was decreased in Lnc RNA (+) group but increased in Lnc RNA (-) group at 72 hours compared to the corresponding control groups.

CONCLUSION

Lnc-SOX6-1 is highly expressed and correlates with worse risk stratification and poor treatment outcomes, and promotes cell proliferation while represses apoptosis in pediatric AML.

Occurrence of Treatment-Related Cardiotoxicity and Its Impact on Outcomes Among Children Treated in the AAML0531 Clinical Trial: A Report From the Children's Oncology Group

PURPOSE

Late cardiotoxicity after pediatric acute myeloid leukemia therapy causes substantial morbidity and mortality. The impact of early-onset cardiotoxicity on treatment outcomes is less well understood. Thus, we evaluated the risk factors for incident early cardiotoxicity and the impacts of cardiotoxicity on event-free survival (EFS) and overall survival (OS).

METHODS

Cardiotoxicity was ascertained through adverse event monitoring over the course of follow-up among 1,022 pediatric patients with acute myeloid leukemia treated in the Children's Oncology Group trial AAML0531. It was defined as grade 2 or higher left ventricular systolic dysfunction on the basis of Common Terminology Criteria for Adverse Events (version 3) definitions.

RESULTS

Approximately 12% of patients experienced cardiotoxicity over a 5-year follow-up, with more than 70% of incident events occurring during on-protocol therapy. Documented cardiotoxicity during on-protocol therapy was significantly associated with subsequent off-protocol toxicity. Overall, the incidence was higher among noninfants and black patients, and in the setting of a bloodstream infection. Both EFS (hazard ratio [HR], 1.6; 95% CI, 1.2 to 2.1; P = .004) and OS (HR, 1.6; 95% CI, 1.2 to 2.2, P = .005) were significantly worse in patients with documented cardiotoxicity. Impacts on EFS were equivalent whether the incident cardiotoxicity event occurred in the absence (HR, 1.6; 95% CI, 1.1 to 2.2; P = .017) or presence of infection (HR, 1.6; 95% CI, 1.0 to 2.7; P = .069) compared with patients without documented cardiotoxicity. However, the reduction in OS was more pronounced for cardiotoxicity not associated with infection (HR, 1.7; 95% CI, 1.2 to 2.5; P = .004) than for infection-associated cardiotoxicity (HR, 1.3; 95% CI, 0.7 to 2.4; P = .387).

CONCLUSION

Early treatment-related cardiotoxicity may be associated with decreased EFS and OS. Cardioprotective strategies are urgently needed to improve relapse risk and both short- and long-term mortality outcomes.

Targeting Oncogenic Signaling in Mutant FLT3 Acute Myeloid Leukemia: The Path to Least Resistance

The identification of recurrent driver mutations in genes encoding tyrosine kinases has resulted in the development of molecularly-targeted treatment strategies designed to improve outcomes for patients diagnosed with acute myeloid leukemia (AML). The receptor tyrosine kinase FLT3 is the most commonly mutated gene in AML, with internal tandem duplications within the juxtamembrane domain (FLT3-ITD) or missense mutations in the tyrosine kinase domain (FLT3-TKD) present in 30–35% of AML patients at diagnosis. An established driver mutation and marker of poor prognosis, the FLT3 tyrosine kinase has emerged as an attractive therapeutic target, and thus, encouraged the development of FLT3 tyrosine kinase inhibitors (TKIs). However, the therapeutic benefit of FLT3 inhibition, particularly as a monotherapy, frequently results in the development of treatment resistance and disease relapse. Commonly, FLT3 inhibitor resistance occurs by the emergence of secondary lesions in the FLT3 gene, particularly in the second tyrosine kinase domain (TKD) at residue Asp835 (D835) to form a ‘dual mutation’ (ITD-D835). Individual FLT3-ITD and FLT3-TKD mutations influence independent signaling cascades; however, little is known about which divergent signaling pathways are controlled by each of the FLT3 specific mutations, particularly in the context of patients harboring dual ITD-D835 mutations. This review provides a comprehensive analysis of the known discrete and cooperative signaling pathways deregulated by each of the FLT3 specific mutations, as well as the therapeutic approaches that hold the most promise of more durable and personalized therapeutic approaches to improve treatments of FLT3 mutant AML.

Diagnostic and prognostic relevance of serum miR-195 in pediatric acute myeloid leukemia

BACKGROUND

MicroRNA-195 acts as a tumor suppressor in a variety of cancers. However, its clinical significance in pediatric acute myeloid leukemia (AML) remains largely undefined.

OBJECTIVE

To investigate the diagnostic and prognostic relevance of miR-195 in this malignancy.

METHODS

Expression levels of miR-195 in peripheral blood and bone marrow samples of patients with pediatric AML and normal controls were detected by real-time quantitative PCR. Then, receiver-operating characteristic (ROC) curve analysis, Kaplan-Meier method, and Cox regression analysis were performed to evaluate the diagnostic and prognostic relevance of serum miR-195 in pediatric AML.

RESULTS

Compared to normal controls, the expression levels of miR-195 in both bone marrow and patients' sera were significantly decreased (both P< 0.001). In addition, serum miR-195 had an optimal diagnostic cut-off point (2.09) for pediatric AML with sensitivity of 68.87% and specificity of 96.23%. The area under the ROC curve (AUC) based on serum miR-195 was 0.910. Moreover, patients with low serum miR-195 level more often had French-American-British classification subtype M7 (P= 0.02), unfavorable karyotypes (P= 0.01), and shorter relapse-free and overall survivals (both P= 0.001) than those with high serum miR-195 level. Furthermore, the multivariate analysis identified serum miR-195 level as an independent prognostic factor for both relapse-free and overall survivals.

CONCLUSION

The findings of this study suggest that the aberrant expression of miR-195 may play crucial roles in the development and progression of pediatric AML patients. Serum miR-195 may serve as a promising marker for monitoring the occurrence of this disease and predicting the clinical outcome of patients.

Current Management of Childhood Acute Myeloid Leukemia

The outcome for children with acute myeloid leukemia (AML) has improved significantly over the past 30 years, with complete remission and overall survival rates exceeding 90 and 60%, respectively, in recent clinical trials. However, these improvements have not been achieved by the introduction of new agents. Instead, intensification of standard chemotherapy, more precise risk classification, improvements in supportive care, and the use of minimal residual disease to monitor response to therapy have all contributed to this success. Nevertheless, novel therapies are needed, as the cure rates for many subtypes of childhood AML remain unacceptably low. Here, we briefly review advances in our understanding of the biology and genetics of AML, the results of recent clinical trials, and current recommendations for the treatment of children with AML.

[An immunological approach to acute myeloid leukaemia]

INTRODUCTION

Acute myeloid leukaemia (AML) is the second haematological malignancy in the paediatric population, and one of the leading causes of childhood cancer mortality. Survival is currently around 60%, with no improvement in last decades, suggesting that new therapeutic approaches are needed. The anti-leukaemia effect mediated by the lymphocytes and natural killer (NK) cells of the immune system has been established in haematopoietic stem cell transplantation, and also as adoptive immunotherapy after consolidation chemotherapy schemes.

PATIENTS AND METHODS

A retrospective study was conducted on the clinical characteristics of patients diagnosed and treated for AML in our centre during 1996-2014. The mean fluorescence intensities of HLA-I, MICA/B and ULBP1-4, ligands for NK cell receptors, were also analysed in ten new diagnosed leukaemia cases, five myeloid and five lymphoid.

RESULTS

A total of 67 patients were used in this analysis. With a median follow up of 25 months, the event-free survival was 62% (95% CI: 55-67). Secondary AML, non-M3 phenotype, and the absence of favourable cytogenetic markers had a lower survival. The probability of relapse was 38% (95% CI: 31-45). The expression of HLA-I and ULBP-4 was significantly lower in myeloid than in lymphoid blast cells.

CONCLUSIONS

Our clinical results are similar to those described in the literature. Survival did not significantly change in recent decades, and the likelihood of relapse remains high. Myeloid blasts might be more susceptible to the cytotoxicity of NK cells through their lower expression of HLA-I. NK therapy strategies in minimal disease situation could be effective, as reported by other groups.