Genomic Variants of Cytarabine Sensitivity Associated with Treatment-Related Mortality in Pediatric AML: A Report from the Children's Oncology Group

PURPOSE

Cytarabine is an effective treatment for AML with associated toxicities including treatment related mortality (TRM). The purpose is to determine the clinical relevance of SNPs identified through the use of HapMap lymphoblastoid cell-based models, in predicting cytarabine response and toxicity in AML.

EXPERIMENTAL DESIGN

We tested clinical significance of SNPs associated with cytarabine sensitivity in children with AML treated on Children's Oncology Group regimens (CCG 2941/2961). Endpoints included overall survival (OS), event-free survival (EFS), and TRM. Patients who received bone marrow transplant were excluded. We tested 124 SNPs associated with cytarabine sensitivity in HapMap cell lines in 348 children to determine whether any associated with treatment outcomes. In addition, we tested five SNPs previously associated with TRM in children with AML in our independent dataset of 385 children.

RESULTS

Homozygous variant genotypes of rs2025501 and rs6661575 had increased in vitro cellular sensitivity to cytarabine and were associated with increased TRM. TRM was particularly increased in children with variant genotype randomized to high-dose cytarabine (rs2025501: P = 0.0024 and rs6661575 P = 0.0188). In analysis of previously reported SNPs, only the variant genotype rs17202778 C/C was significantly associated with TRM (P < 0.0001).

CONCLUSIONS

We report clinical importance of two SNPs not previously associated with cytarabine toxicity. Moreover, we confirm that SNP rs17202778 significantly impacts TRM in pediatric AML. Cytarabine sensitivity genotypes may predict TRM and could be used to stratify to standard versus high-dose cytarabine regimens, warranting further study in prospective AML trials.

Comprehensive Transcriptome Profiling of Cryptic CBFA2T3-GLIS2 Fusion-Positive AML Defines Novel Therapeutic Options: A COG and TARGET Pediatric AML Study

PURPOSE

A cryptic inv(16)(p13.3q24.3) encoding the CBFA2T3-GLIS2 fusion is associated with poor outcome in infants with acute megakaryocytic leukemia. We aimed to broaden our understanding of the pathogenesis of this fusion through transcriptome profiling.

EXPERIMENTAL DESIGN

Available RNA from children and young adults with de novo acute myeloid leukemia (AML; N = 1,049) underwent transcriptome sequencing (mRNA and miRNA). Transcriptome profiles for those with the CBFA2T3-GLIS2 fusion (N = 24) and without (N = 1,025) were contrasted to define fusion-specific miRNAs, genes, and pathways. Clinical annotations defined distinct fusion-associated disease characteristics and outcomes.

RESULTS

The CBFA2T3-GLIS2 fusion was restricted to infants <3 years old (P < 0.001), and the presence of this fusion was highly associated with adverse outcome (P < 0.001) across all morphologic classifications. Further, there was a striking paucity of recurrent cooperating mutations, and transduction of cord blood stem cells with this fusion was sufficient for malignant transformation. CBFA2T3-GLIS2 positive cases displayed marked upregulation of genes with cell membrane/extracellular matrix localization potential, including NCAM1 and GABRE. Additionally, miRNA profiling revealed significant overexpression of mature miR-224 and miR-452, which are intronic miRNAs transcribed from the GABRE locus. Gene-set enrichment identified dysregulated Hippo, TGFβ, and hedgehog signaling, as well as NCAM1 (CD56) interaction pathways. Therapeutic targeting of fusion-positive leukemic cells with CD56-directed antibody-drug conjugate caused significant cytotoxicity in leukemic blasts.

CONCLUSIONS

The CBFA2T3-GLIS2 fusion defines a highly refractory entity limited to infants that appears to be sufficient for malignant transformation. Transcriptome profiling elucidated several highly targetable genes and pathways, including the identification of CD56, providing a highly plausible target for therapeutic intervention.

Deciphering the Significance of CD56 Expression in Pediatric Acute Myeloid Leukemia: A Report from the Children's Oncology Group

BACKGROUND

In patients with acute myeloid leukemia (AML), CD56 expression has been associated with adverse clinical outcome. We reported on a phenotype associated with very poor prognosis (RAM) in children enrolled in the Children's Oncology Group trial AAML0531 (Brodersen et al. Leukemia 30 (2016) 2077-2080). RAM is also characterized in part by high-intensity expression of the CD56 antigen. Herein, we investigate underlying biological and clinical differences among CD56-positive AMLs for patients in AAML0531.

METHODS

For 769 newly diagnosed pediatric patients with de novo AML enrolled in AAML0531, bone marrow specimens were submitted for flow cytometric analysis. For each patient, an immunophenotypic expression profile (IEP) was defined by mean fluorescent intensities of assayed surface antigens. Unsupervised hierarchical clustering analysis (HCA) was completed to group patients with similar immunophenotypes. Clusters were then evaluated for CD56 expression. Principal component analysis (PCA) was subsequently applied to determine whether CD56-positive patient groups were nonoverlapping.

RESULTS

HCA of IEPs revealed three unique phenotypic clusters of patients with CD56-positive AML, and PCA showed that these three cohorts are distinct. Cohort 1 (N = 77) showed a prevalence of t(8;21) patients (72%), Cohort 2 (N = 52) a prevalence of 11q23 patients (69%), and Cohort 3 (RAM) (N = 16) a prevalence of patients with co-occurrence of the CBFA2T3-GLIS2 fusion transcript (63%). The 5-year event-free survival (EFS) for Cohorts 1, 2, and 3 were 69, 39, and 19%, respectively.

CONCLUSIONS

When leukemia is considered by its multidimensional immunophenotype and not by the expression of a single antigen, correlations are seen between genotype and there are significant differences in patient outcomes. © 2019 International Clinical Cytometry Society.

Functional Properties of KIT Mutations Are Associated with Differential Clinical Outcomes and Response to Targeted Therapeutics in CBF Acute Myeloid Leukemia

PURPOSE

KIT mutations (KIT ⁺) are common in core binding factor (CBF) AML and have been associated with varying prognostic significance. We sought to define the functional and clinical significance of distinct KIT mutations in CBF pediatric AML.

EXPERIMENTAL DESIGN

Following transfection of exon 17 (E17) and exon 8 (E8) mutations into HEK293 and Ba/F3 cells, KIT phosphorylation, cytokine-independent growth, and response to tyrosine kinase inhibitors (TKI) were evaluated. Clinical outcomes of patients treated on COG AAML0531 (NCT01407757), a phase III study of gemtuzumab ozogamicin (GO), were analyzed according to mutation status [KIT ⁺ vs. wild-type KIT (KIT ^-)] and mutation location (E8 vs. E17).

RESULTS

KIT mutations were detected in 63 of 205 patients (31%); 22 (35%) involved only E8, 32 (51%) only E17, 6 (10%) both exons, and 3 (5%) alternative exons. Functional studies demonstrated that E17, but not E8, mutations result in aberrant KIT phosphorylation and growth. TKI exposure significantly affected growth of E17, but not E8, transfected cells. Patients with KIT ⁺ CBF AML had overall survival similar to those with KIT ^- (78% vs. 81%, P = 0.905) but higher relapse rates (RR = 43% vs. 21%; P = 0.005). E17 KIT ⁺ outcomes were inferior to KIT ^- patients [disease-free survival (DFS), 51% vs. 73%, P = 0.027; RR = 21% vs. 46%, P = 0.007)], although gemtuzumab ozogamicin abrogated this negative prognostic impact. E8 mutations lacked significant prognostic effect, and GO failed to significantly improve outcome.

CONCLUSIONS

E17 mutations affect prognosis in CBF AML, as well as response to GO and TKIs; thus, clinical trials using both agents should be considered for KIT ⁺ patients.

AAML 1421, a phase I/II study of CPX-351 followed by fludarabine, cytarabine, and G-CSF (FLAG) for children with relapsed acute myeloid leukemia (AML): A Report from the Children’s Oncology Group

10003

Background: Effective regimens with favorable toxicity profiles are needed for heavily pre-treated children with relapsed AML. AAML1421 is a Phase I/II study of CPX-351, a liposomal preparation of cytarabine and daunorubicin demonstrating efficacy in adults. AAML1421 sought to determine the recommended Phase 2 Dose (RPD2) of CPX-351 and the response rate (complete response (CR) + complete response without platelet recovery (CRp)) after up to 2 cycles of therapy. Methods: Children > 1 and ≤ 21 years of age with relapsed/refractory AML were eligible for dose finding, and those in first relapse were eligible for efficacy. A modified rolling six design was used for dose-limiting toxicity (DLT) assessment which occurred in Cycle 1. Dose level 1 (DL1) was 135 units/m2 on days 1, 3, and 5 with a single dose de-escalation to 100 units/m2 if DL1 was intolerable. The Efficacy Phase used a Simon-two stage design. The response rate was determined after up to 2 cycles of therapy (Cycle 1: CPX-351; Cycle 2: FLAG). The Overall Response Rate (ORR) was defined as CR+CRp+CRi (CRi = CR with incomplete hematologic recovery). Results: Thirty-eight patients (pts) enrolled: 6 in dose-finding and 32 in the efficacy phase. DLT occurred in 1/6 patients and was a grade 3 decrease in ejection fraction(EF). This was the only Grade 3 cardiac toxicity. Therefore, 135 units/m2 on days 1, 3, 5 was the RP2D. All dose finding pts were eligible for efficacy determination. One pt in the efficacy phase was unevaluable. The most common ≥ Grade 3 toxicities in Cycle 1 included fever/neutropenia (45%), infection (47%), and rash (40%). There was no toxic mortality. Best responses included 20 CR (54%), 5 CRp (14%), and 5 CRi (14%). Seventy percent achieved best response after cycle 1. Twenty-one of 25 patients with CR/CRp had no detectable residual disease (RD) (84%) by flow cytometry. HSCT was used as consolidation in 23/29 responders (79%); 18 of 23 (78%) had no detectable RD prior to HSCT. Conclusions: The RP2D of CPX-351 is 135 units/m2/dose on days 1, 3, 5. CPX-351 was well tolerated and protocol therapy was effective with CR+CRp rates of 68.3% (90% CI 52.9% to 78.0%) and ORR (CR+CRp+CRi) of 81.1% (90% CI 67.4% to 88.8%). AAML1421 response rates are superior to any published North American cooperative group clinical trial for children with AML in first relapse. Clinical trial information: NCT02642965.

Effect of intensification of induction II chemotherapy and liberalization of stem cell donor source on outcome for children with high risk acute myeloid leukemia: A report from the Children’s Oncology Group

10002

Background: Patients with residual acute myeloid leukemia (AML) after induction fare poorly. The recently completed AAML1031 Phase III clinical trial intensified Induction II chemotherapy, altered the stem cell transplant (SCT) conditioning regimen, and liberalized SCT donor source criteria. We sought to test whether these practice changes improved clinical outcomes. Methods: Patients on AAML0531 and AAML1031, sequential Phase III trials for AML with shared high risk features of both > 15% residual blasts by morphology and ≥ 0.1% minimal residual disease (MRD) by flow cytometry with uninformative cytogenetics or high risk cytogenetic features (-7 or -5/5q-) were included. Gemtuzmab exposed and patients with high allelic ratio FLT3 ITD were excluded. Patients were observed from the start of Induction II through last available follow up. Induction II chemotherapy (ADE or AraC/Mito) was the exposure of interest. Disease free and overall survival (DFS, OS) were the primary outcomes. Standard descriptive statistics were used to compare patient characteristics and secondary outcomes; Kaplan Meier analyses were used to evaluate DFS/OS. Results: A total of 47 patients from AAML0531 (ADE) and 95 patients from AAML1031 (AraC/Mito) were included and did not differ in baseline characteristics. Five year DFS ±2SE was 17.5 ± 11.4 for ADE and 23.9 ± 8.8 for AraC/Mito, p = 0.528. Five year OS was 38.1 ± 14.2 for ADE and 33.3 ± 10.7 for AraC/Mito, p = 0.364. End of Induction II disease response and MRD did not differ between ADE and AraC/Mito. Patients receiving ADE had a higher probability of neutrophil recovery (74% vs 53%, p = 0.019) and recovered neutrophils a median of 7 days more quickly (27 vs 34 days), p = < 0.001. ADE patients also had fewer inpatient hospital days (28 days versus 32 days, p = 0.002). The percentage of patients receiving SCT did not differ, 34% vs 44%, p = 0.253 and post-SCT outcomes did not differ. Conclusions: The intensification of Induction II chemotherapy, change in SCT conditioning regimen, and liberalization of SCT donor source was not associated with improved clinical outcomes. Intensification of Induction II was associated with increased hematologic toxicity and length of stay. These data do not support the intensification of Induction II chemotherapy with AraC/Mitoxantrone. Clinical trial information: NCT01371981.

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.

Abstract 3550: Lipid rafts contribute to ligand-induced signaling and survival in pediatric AML

Pediatric acute myeloid leukemia (pAML) is an aggressive malignancy with high mortality due to therapy resistance and relapse. We previously reported that the failure of pAML cells to phosphorylate STAT3 upon G-CSF or IL-6 stimulation was associated with inferior survival. The defect in STAT3 signaling was not due to low expression of receptors or of STAT3. We hypothesized that the signaling failure seen in some pAML samples is not specific for STAT3, but rather a generalized dysfunction due to abnormal lipid raft function. Lipid rafts (LR) are highly ordered plasma membrane microdomains rich in glycosphingolipids and cholesterol. Two types of LR - flat planar and invaginated caveolar - contain different membrane proteins and serve distinct but overlapping cellular functions. Both types of LR organize receptors, downstream mediators, and repressors for efficient signaling. The role of LRs in signaling and clinical outcome is not yet established in pAML. Primary samples (n=95) from the Children's Oncology Group (COG) were stimulated with HS5 stromal cell conditioned medium (HS5CM), which contains IL-6 and dozens of physiological ligands. Basal and induced phospho-STAT3 (pSTAT3), pSTAT5, pAKT and pERK1/2 were measured by intracellular flow cytometry, and the fold change in the mean fluorescence intensity (ΔMFI) was calculated. The HS5CM-induced ΔMFI for pSTAT3 was positively correlated with that for pSTAT5 (p&lt;0.0001, r=0.5), and pAKT (p=0.0002, r=0.4). Samples that failed to increase pSTAT3 failed to activate other pathways, suggesting a generalized signaling dysfunction. In AML cells with intact signaling, disruption of LRs with methylβcyclodextrin markedly reduced HS5CM-induced pSTATs, recapitulating the dysfunctional phenotype. LRs were assessed by immunocytochemistry in 29 primary samples with and without HS5CM stimulation. Choleratoxin B, which binds ganglioside GM-1, stained LRs. Antibodies to caveolin-1 (cav-1) marked caveolar LRs. We also stained for gp130, the signaling subunit of the IL-6 receptor. Images were captured by deconvolution fluorescence microscopy. Expression was quantified by pixel intensity for average of 30 cells per condition. Colocalization of gp130 with LR markers was determined by the Manders Overlap Coefficient (MOC). Intensities and MOCs varied between samples. The MOC of gp130 with cav-1 correlated significantly with pSTAT3 ΔMFI (p=0.02, r=0.43). MOC of gp130 with GM-1 did not correlate with pSTAT3 ΔMFI (p=0.85, r=0.03), suggesting that cav-1 facilitates IL-6/STAT3 signaling. Interestingly, patients whose samples demonstrated basal cav-1 and GM-1 intensities below the median had inferior 5-year event-free survival compared to those with intensities above the median (log-rank p=0.079 for cav-1; p=0.013 for GM-1). Our results suggest that LRs contribute to ligand-induced signaling and possibly to chemotherapy response. Further studies of LR biology in AML are warranted.

Citation Format: Padmini Narayanan, Julien Dubrulle, Robert B. Gerbing, Todd A. Alonzo, Fabio Stossi, Michele S. Redell. Lipid rafts contribute to ligand-induced signaling and survival in pediatric AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3550.

Shorter Remission Telomere Length Predicts Delayed Neutrophil Recovery After Acute Myeloid Leukemia Therapy: A Report From the Children's Oncology Group

Purpose Suboptimal outcomes for children with acute myeloid leukemia (AML) necessitate maximally intensive therapy. Consequently, serious adverse events, such as prolonged periods of profound myelosuppression, contribute to AML treatment-related mortality. Telomeres, the repetitive DNA-protein structures at chromosome ends, influence cellular replicative capacity in that critically short telomeres can induce cell senescence or apoptosis. Our objective was to evaluate the impact of telomere length on duration of post-therapy neutropenia in a pediatric AML cohort. Patients and Methods Patients were diagnosed with de novo AML, enrolled in Children's Oncology Group study AAML0531, and included those with (n = 53) and without (n = 62) significantly delayed neutrophil recovery after chemotherapy. We used quantitative polymerase chain reaction to measure telomere content (TC), a validated proxy for telomere length, from remission bone marrow samples obtained after the second induction chemotherapy course. Results Less TC was significantly associated with prolonged neutropenia after the fourth ( P < .001) and fifth chemotherapy courses ( P = .002). Cox regression adjusting for age at diagnosis confirmed that TC remained independently predictive of time to recovery of absolute neutrophil count for both the fourth and fifth courses ( P = .002 and .009, respectively). DNA from patients was analyzed for germline mutations in four telomere maintenance genes associated with telomere biology disorders. Sequence analysis revealed no enrichment of rare or novel variants in the delayed recovery group. Conclusion Our results suggest that TC at end of AML induction is associated with hematopoietic reconstitution capacity independently of age and may identify those at highest risk for markedly delayed bone marrow recovery after AML therapy.

MicroRNA Expression-Based Model Indicates Event-Free Survival in Pediatric Acute Myeloid Leukemia

Purpose Children with acute myeloid leukemia (AML) whose disease is refractory to standard induction chemotherapy therapy or who experience relapse after initial response have dismal outcomes. We sought to comprehensively profile pediatric AML microRNA (miRNA) samples to identify dysregulated genes and assess the utility of miRNAs for improved outcome prediction. Patients and Methods To identify miRNA biomarkers that are associated with treatment failure, we performed a comprehensive sequence-based characterization of the pediatric AML miRNA landscape. miRNA sequencing was performed on 1,362 samples-1,303 primary, 22 refractory, and 37 relapse samples. One hundred sixty-four matched samples-127 primary and 37 relapse samples-were analyzed by using RNA sequencing. Results By using penalized lasso Cox proportional hazards regression, we identified 36 miRNAs the expression levels at diagnosis of which were highly associated with event-free survival. Combined expression of the 36 miRNAs was used to create a novel miRNA-based risk classification scheme (AMLmiR36). This new miRNA-based risk classifier identifies those patients who are at high risk (hazard ratio, 2.830; P ≤ .001) or low risk (hazard ratio, 0.323; P ≤ .001) of experiencing treatment failure, independent of conventional karyotype or mutation status. The performance of AMLmiR36 was independently assessed by using 878 patients from two different clinical trials (AAML0531 and AAML1031). Our analysis also revealed that miR-106a-363 was abundantly expressed in relapse and refractory samples, and several candidate targets of miR-106a-5p were involved in oxidative phosphorylation, a process that is suppressed in treatment-resistant leukemic cells. Conclusion To assess the utility of miRNAs for outcome prediction in patients with pediatric AML, we designed and validated a miRNA-based risk classification scheme. We also hypothesized that the abundant expression of miR-106a could increase treatment resistance via modulation of genes that are involved in oxidative phosphorylation.

Central nervous system disease in pediatric acute myeloid leukemia: A report from the Children's Oncology Group

BACKGROUND

The prognostic impact of central nervous system (CNS) involvement in children with acute myeloid leukemia (AML) has varied in past trials, and controversy exists over the degree of involvement requiring intensified CNS therapy. Two recent Children's Oncology Group protocols, AAML03P1 and AAML0531, directed additional intrathecal (IT) therapy to patients with CNS2 (≤5 white blood cell [WBC] with blasts) or CNS3 (>5 WBC with blasts or CNS symptoms) disease at diagnosis.

METHODS

We examined disease characteristics and outcomes of the 1,344 patients on these protocols, 949 with CNS1 (no blasts), 217 with CNS2, and 178 with CNS3, with the latter two receiving additional IT therapy.

RESULTS

Young age (P = 0.003), hyperleukocytosis (P < 0.001), and the presence of inversion 16 (P < 0.001) were the only factors more prevalent in patients with CNS2 or CNS3 disease. Complete remission at the end of induction (EOI) 2 was achieved less often in patients with CNS involvement (P < 0.001). From diagnosis, event-free survival (EFS) for patients with CNS involvement was significantly worse (P < 0.001), whereas overall survival (OS) was not (P = 0.16). From the EOI1, there was a higher relapse rate (RR) and worse disease-free survival (DFS), but less impact on OS (CNS1:DFS 58.9%, RR 34.1%, OS 69.3%; CNS2:DFS 53.2%, RR 40.9%, OS 74.7%; CNS3:DFS 45.2%, RR 48.8%, OS 60.8%; P = 0.006, P < 0.001, P = 0.045, respectively). Multivariable analysis showed that independently CNS2 and CNS3 status adversely affected RR and DFS. Traumatic diagnostic lumbar puncture was not associated with worse outcome.

CONCLUSIONS

CNS leukemia confers greater relapse risk despite more aggressive locally directed therapy. Novel approaches need to be investigated in this group of patients.

Phenotype in combination with genotype improves outcome prediction in acute myeloid leukemia: a report from Children's Oncology Group protocol AAML0531

Diagnostic biomarkers can be used to determine relapse risk in acute myeloid leukemia, and certain genetic aberrancies have prognostic relevance. A diagnostic immunophenotypic expression profile, which quantifies the amounts of distinct gene products, not just their presence or absence, was established in order to improve outcome prediction for patients with acute myeloid leukemia. The immunophenotypic expression profile, which defines each patient’s leukemia as a location in 15-dimensional space, was generated for 769 patients enrolled in the Children’s Oncology Group AAML0531 protocol. Unsupervised hierarchical clustering grouped patients with similar immunophenotypic expression profiles into eleven patient cohorts, demonstrating high associations among phenotype, genotype, morphology, and outcome. Of 95 patients with inv(16), 79% segregated in Cluster A. Of 109 patients with t(8;21), 92% segregated in Clusters A and B. Of 152 patients with 11q23 alterations, 78% segregated in Clusters D, E, F, G, or H. For both inv(16) and 11q23 abnormalities, differential phenotypic expression identified patient groups with different survival characteristics (P<0.05). Clinical outcome analysis revealed that Cluster B (predominantly t(8;21)) was associated with favorable outcome (P<0.001) and Clusters E, G, H, and K were associated with adverse outcomes (P<0.05). Multivariable regression analysis revealed that Clusters E, G, H, and K were independently associated with worse survival (P range <0.001 to 0.008). The Children’s Oncology Group AAML0531 trial: clinicaltrials.gov Identifier: 00372593.

Arsenic Trioxide Consolidation Allows Anthracycline Dose Reduction for Pediatric Patients With Acute Promyelocytic Leukemia: Report From the Children's Oncology Group Phase III Historically Controlled Trial AAML0631

Purpose The Children's Oncology Group AAML0631 trial for newly diagnosed pediatric acute promyelocytic leukemia (APL) was a phase III historically controlled trial to determine the survival of patients receiving arsenic trioxide (ATO) consolidation and reduced doses of anthracyclines. Patients and Methods Patients age 2 to 21 years with de novo APL confirmed by PML-RARα polymerase chain reaction were stratified as standard risk (SR) or high risk (HR) on the basis of diagnostic WBC count. All patients received all-trans retinoic acid (ATRA) during induction, each consolidation course, and maintenance. All patients received two cycles of ATO therapy during consolidation 1, an additional two (SR) or three (HR) consolidation courses that included high-dose cytarabine and anthracycline, and maintenance therapy comprising ATRA, oral methotrexate, and mercaptopurine. Results One hundred one patients (66 SR and 35 HR) were evaluable for outcome. The 3-year overall survival was 94%, and event-free survival (EFS) was 91%. For SR and HR patients with APL, the overall survival was 98% versus 86% ( P = .003), and EFS was 95% versus 83% ( P = .03), respectively. The EFS for SR patients in AAML0631 was noninferior to that of patients in the AIDA 0493 historical control, which used a significantly higher anthracycline dose and did not include ATO consolidation. Relapse risk for patients in AAML0631 from end consolidation 1 (after ATO treatment) was only 4% at 3 years and did not differ significantly between SR and HR patients. Conclusion ATO consolidation cycles were well tolerated in pediatric patients with APL and allowed significant reduction in cumulative anthracycline doses while maintaining excellent survival and a low relapse risk for both SR and HR patients with APL.

Four versus five chemotherapy courses in patients with low risk acute myeloid leukemia: A Children’s Oncology Group report

10515

Background: For pediatric patients with low risk (LR) acute myeloid leukemia (AML), the Children’s Oncology Group (COG) trial AAML1031 used a 4-course chemotherapy backbone consisting of two induction courses of cytarabine/daunorubicin/etoposide, a third course of cytarabine/etoposide and a fourth course of cytarabine/mitoxantrone. The prior COG trial, AAML0531, included the same four courses plus a fifth course of high dose cytarabine. Removal of course 5 from AAML1031 was based in part on prior studies that suggested no benefit from a fifth course. Methods: We compared overall survival (OS), disease free survival (DFS), and relapse risk (RR) for LR patients receiving four versus five chemotherapy courses in a pooled analysis of comparable patients treated on AAML0531 and AAML1031. LR was defined as the presence of inv(16)/t(16;16) or t(8;21) cytogenetic features, NPM1 or CEBPA mutations, or MRD < 0.1% post-Induction I in those with no high risk features. AAML0531 patients assigned to gemotuzumab were excluded. Follow-up for outcomes began at the start of course 4. Cox (OS and EFS) and risk (RR) regressions were used to estimate unadjusted hazard ratios (HR) comparing outcomes for patients who received only four versus five chemotherapy courses. Start of a fifth chemotherapy course was assessed as a time-varying exposure in all analyses to avoid exposure misclassification. Results: A total of 921 LR patients (225 from AAML0531, 696 from AAML1031) were included; 191 (21%) received a fifth course. There were no significant differences in distributions of sex, age, race, or ethnicity between patients treated with four or five courses. Median times to absolute neutrophil count and platelet count recovery after course 4 were also comparable. Patients who received only four courses had significantly lower OS (HR = 1.83, 95% CI: 1.22-2.74, p = 0.003), DSF (HR = 1.49, 95% CI: 1.13-1.97, p = 0.005), and higher RR (HR = 1.42, 95% CI: 1.08-1.88, p = 0.013) compared to those who received five courses. Conclusions: Removal of a fifth cytarabine-containing course appears to result in worse OS, DFS, and RR in pediatric patients with LR AML. Multivariable analyses to further refine the estimates are ongoing.

Disease Characteristics and Prognostic Implications of Cell-Surface FLT3 Receptor (CD135) Expression in Pediatric Acute Myeloid Leukemia: A Report from the Children's Oncology Group

Purpose: The FLT3 cell-surface receptor tyrosine kinase (CD135) is expressed in a majority of both acute lymphoid leukemia (ALL) and myeloid leukemia (AML). However, the prognostic significance of CD135 expression in AML remains unclear. We therefore evaluated the association between FLT3 surface expression and disease characteristics and outcomes in pediatric patients with AML.Experimental Design: We analyzed FLT3 receptor expression on AML blasts by multi-dimensional flow cytometry and its association with disease characteristics, clinical outcomes, and FLT3 transcript level in 367 children with AML treated on the Children's Oncology Group trial AAML0531.Results: There was high variability in blast CD135 cell-surface expression across specimens. CD135 expression measured by flow cytometry was not correlated with FLT3 transcript expression determined by quantitative RT-PCR. Overall, CD135 expression was not significantly different for patients with FLT3/WT, FLT3/ITD, or FLT3/ALM (P = 0.25). High cell-surface CD135 expression was associated with FAB M5 subtype (P < 0.001), KMT2A rearrangements (P = 0.009), and inversely associated with inv(16)/t(16;16) (P < 0.001). Complete remission rate, overall survival, disease-free survival, and relapse rates were not significantly different between patients with low and high CD135 expression.Conclusions: FLT3 cell-surface expression did not vary by FLT3 mutational status, but high FLT3 expression was strongly associated with KMT2A rearrangements. Our study found that there was no prognostic significance of FLT3 cell surface expression in pediatric AML. Clin Cancer Res; 23(14); 3649-56. ©2017 AACR.

miR-155 expression and correlation with clinical outcome in pediatric AML: A report from Children's Oncology Group

BACKGROUND

Aberrant expression of microRNA-155 (miR-155) has been implicated in acute myeloid leukemia (AML) and associated with clinical outcome.

PROCEDURE

We evaluated miR-155 expression in 198 children with normal karyotype AML (NK-AML) enrolled in Children's Oncology Group (COG) AML trial AAML0531 and correlated miR-155 expression levels with disease characteristics and clinical outcome. Patients were divided into quartiles (Q1-Q4) based on miR-155 expression level, and disease characteristics were then evaluated and correlated with miR-155 expression.

RESULTS

MiR-155 expression varied over 4-log10-fold range relative to its expression in normal marrow with a median expression level of 0.825 (range 0.043-25.630) for the entire study cohort. Increasing miR-155 expression was highly associated with the presence of FLT3/ITD mutations (P < 0.001) and high-risk disease (P < 0.001) and inversely associated with standard-risk (P = 0.008) and low-risk disease (P = 0.041). Patients with highest miR-155 expression had a complete remission (CR) rate of 46% compared with 82% in low expressers (P < 0.001) with a correspondingly lower event-free (EFS) and overall survival (OS) (P < 0.001 and P = 0.002, respectively). In a multivariate model that included molecular risk factors, high miR-155 expression remained a significant independent predictor of OS (P = 0.022) and EFS (0.019).

CONCLUSIONS

High miR-155 expression is an adverse prognostic factor in pediatric NK-AML patients. Specifically, high miR-155 expression not only correlates with FLT3/ITD mutation status and high-risk disease but it is also an independent predictor of worse EFS and OS.

Association between prolonged neutropenia and reduced relapse risk in pediatric AML: A report from the children's oncology group

Objective was to describe the relationship between the number of sterile site infections and duration of neutropenia during the first four cycles of chemotherapy and the risk of recurrence and overall survival in children with newly diagnosed acute myeloid leukemia (AML). AAML0531 was a Children's Oncology Group randomized phase 3 clinical trial that included 1022 children with de novo AML. For this analysis, we focused on non-Down syndrome favorable and standard risk patients who completed at least 4 cycles of chemotherapy without recurrence or withdrawal during protocol therapy. Those receiving hematopoietic stem cell transplantation in first remission were excluded. Five hundred and sixty-nine patients were included; 274 (48.2%) were favorable risk. The median cumulative time with neutropenia between Induction II to completion of Intensification II was 96 (range 54-204) days. Number of sterile site infections did not influence the risk of relapse or overall survival. However, longer duration of neutropenia was associated with a lower risk of relapse (hazard ratio 0.81 per 20 days neutropenia, p = 0.007). Longer duration of neutropenia was associated with a reduced risk of relapse for children with favorable and standard risk AML. Toxicity may be influenced by pharmacogenomics suggesting that individualized chemotherapy dosing may be an effective strategy.

CD33 Expression and Its Association With Gemtuzumab Ozogamicin Response: Results From the Randomized Phase III Children's Oncology Group Trial AAML0531

PURPOSE

CD33 is variably expressed on acute myeloid leukemia (AML) blasts and is targeted by gemtuzumab ozogamicin (GO). GO has shown benefit in both adult and pediatric AML trials, yet limited data exist about whether GO response correlates with CD33 expression level.

PATIENTS AND METHODS

CD33 expression levels were prospectively quantified by multidimensional flow cytometry in 825 patients enrolled in Children's Oncology Group AAML0531 and correlated with response to GO.

RESULTS

Patients with low CD33 expression (lowest quartile of expression [Q1]) had no benefit with the addition of GO to conventional chemotherapy (relapse risk [RR]: GO 36% v No-GO 34%, P = .731; event-free survival [EFS]: GO 53% v No-GO 58%, P = .456). However, patients with higher CD33 expression (Q2 to Q4) had significantly reduced RR (GO 32% v No-GO 49%, P < .001) and improved EFS (GO 53% v No-GO 41%, P = .005). This differential effect was observed in all risk groups. Specifically, low-risk (LR), intermediate-risk (IR), and high-risk (HR) patients with low CD33 expression had similar outcomes regardless of GO exposure, whereas the addition of GO to conventional chemotherapy resulted in a significant decrease in RR and disease-free survival (DFS) for patients with higher CD33 expression (LR RR, GO 13% v No-GO 35%, P = .001; LR DFS, GO 79% v No-GO 59%, P = .007; IR RR, GO 44% v No-GO 57%, P = .044; IR DFS, GO 51% v No-GO 40%, P = .078; HR RR, GO 40% v No-GO 73%, P = .016; HR DFS, GO 47% v No-GO 28%, P = .135).

CONCLUSION

We demonstrate that GO lacks clinical benefit in patients with low CD33 expression but significantly reduces RR and improves EFS in patients with high CD33 expression, which suggests a role for CD33-targeted therapeutics in subsets of pediatric AML.

Gemtuzumab Ozogamicin Reduces Relapse Risk in FLT3/ITD Acute Myeloid Leukemia: A Report from the Children's Oncology Group

PURPOSE

Gemtuzumab ozogamicin (GO), a calicheamicin-conjugated mAb against CD33, has been used in the treatment of acute myeloid leukemia (AML). We evaluated the impact of the addition of GO to standard chemotherapy and hematopoietic stem cell transplant (HCT) in patients withFLT3/ITD.

EXPERIMENTAL DESIGN

We analyzed children withFLT3/ITD-positive AML (n= 183) treated on two consecutive Children's Oncology Group AML trials (NCT00070174andNCT00372593). Outcomes were assessed forFLT3/ITD patients receiving standard chemotherapy with or without GO (GO vs. No-GO, respectively), and the impact of consolidation HCT for high-riskFLT3/ITD patients [highFLT3/ITD allelic ratio (ITD-AR)].

RESULTS

For allFLT3/ITD patients, complete remission (CR) rates for the GO versus No-GO cohorts were identical (64% vs. 64%;P= 0.98). Relapse rate (RR) after initial CR was 37% for GO recipients versus 59% for No-GO recipients (P= 0.02), disease-free survival (DFS) was similar (47% vs. 41%;P= 0.45), with higher treatment-related mortality (TRM) in GO recipients (16% vs. 0%;P= 0.008). Among high-riskFLT3/ITD patients with high ITD-AR, those who received HCT in first CR with prior exposure to GO had a significant reduction in RR (15% vs. 53%;P= 0.007), with a corresponding DFS of 65% versus 40% (P= 0.08), and higher TRM (19% vs. 7%;P= 0.08).

CONCLUSIONS

CD33 targeting with HCT consolidation may be an important therapeutic strategy in high-riskFLT3/ITD AML and its efficacy and associated toxicity warrant further investigation.

The genomic landscape of juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative neoplasm (MPN) of childhood with a poor prognosis. Mutations in NF1, NRAS, KRAS, PTPN11 or CBL occur in 85% of patients, yet there are currently no risk stratification algorithms capable of predicting which patients will be refractory to conventional treatment and could therefore be candidates for experimental therapies. In addition, few molecular pathways aside from the RAS-MAPK pathway have been identified that could serve as the basis for such novel therapeutic strategies. We therefore sought to genomically characterize serial samples from patients at diagnosis through relapse and transformation to acute myeloid leukemia to expand knowledge of the mutational spectrum in JMML. We identified recurrent mutations in genes involved in signal transduction, splicing, Polycomb repressive complex 2 (PRC2) and transcription. Notably, the number of somatic alterations present at diagnosis appears to be the major determinant of outcome.

High expression of myocyte enhancer factor 2C (MEF2C) is associated with adverse-risk features and poor outcome in pediatric acute myeloid leukemia: a report from the Children's Oncology Group

Background

Recent studies have identified myocyte enhancer factor 2C (MEF2C) as cooperating oncogene in acute myeloid leukemia (AML) and suggested a contribution to the aggressive nature of at least some subtypes of AML, raising the possibility that MEF2C could serve as marker of poor-risk AML and, therefore, have prognostic significance.

Methods

To test this hypothesis, we retrospectively quantified MEF2C expression in pretreatment bone marrow specimens in participants of the AAML0531 trial by reverse-transcriptase polymerase chain reaction and correlated expression levels with disease characteristics and clinical outcome.

Results

In all 751 available patient specimens, MEF2C messenger RNA (mRNA) was detectable and varied >3000-fold relative to β-glucuronidase. Patients with the highest relative MEF2C expression (4th quartile) less likely achieved a complete remission after one course of chemotherapy than the other patients (67 vs. 78 %, P = 0.005). They also had an inferior overall survival (P = 0.014; at 5 years 55 ± 8 vs. 67 ± 4 %), inferior event-free survival (P < 0.001; at 5 years 38 ± 7 vs. 54 ± 4 %), and higher relapse risk than patients within the lower 3 quartiles of MEF2C expression (P < 0.001; at 5 years 53 ± 9 vs. 35 ± 5 %). These differences were accounted for by lower prevalence of cytogenetically/molecularly defined low-risk disease (16 vs. 46 %, P < 0.001) and higher prevalence of standard-risk disease (68 vs. 42 %, P < 0.001) in patients with high MEF2C expression, suggesting that MEF2C cooperates with additional pathogenic abnormalities.

Conclusions

High MEF2C expression identifies a subset of AML patients with adverse-risk disease features and poor outcome. With confirmation that high MEF2C mRNA expression leads to overexpression of MEF2C protein, these findings provide the rationale for therapeutic targeting of MEF2C transcriptional activation in AML.

Comparison of in-patient costs for children treated on the AAML0531 clinical trial: A report from the Children's Oncology Group

BACKGROUND

A better understanding of drivers of treatment costs may help identify effective cost containment strategies and prioritize resources. We aimed to develop a method for estimating inpatient costs for pediatric patients with acute myeloid leukemia (AML) enrolled on NCI-funded Phase III trials, compare costs between AAML0531 treatment arms (standard chemotherapy ± gemtuzumab ozogamicin (GMTZ)), and evaluate primary drivers of costs for newly diagnosed pediatric AML.

PROCEDURE

Patients from the AAML0531 trial were matched on hospital, sex, and dates of birth and diagnosis to the Pediatric Health Information Systems (PHIS) database to obtain daily billing data. Inpatient treatment costs were calculated as adjusted charges multiplied by hospital-specific cost-to-charge ratios. Generalized linear models were used to compare costs between treatment arms and courses, and by patient characteristics.

RESULTS

Inpatient costs did not differ by randomized treatment arm. Costs varied by course with stem cell transplant being most expensive, followed by Intensification II (cytarabine/mitoxantrone) and Induction I (cytarabine/daunorubicin/etoposide). Room/board and pharmacy were the largest contributors to inpatient treatment cost, representing 74% of the total cost. Higher AML risk group (P = 0.0003) and older age (P < 0.0001) were associated with significantly higher daily inpatient cost.

CONCLUSIONS

Costs from external data sources can be successfully integrated into NCI-funded Phase III clinical trials. Inpatient treatment costs did not differ by GMTZ exposure but varied by chemotherapy course. Variation in cost by course was driven by differences in duration of hospitalization through room/board charges as well as increased clinical and pharmacy charges in specific courses.