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.

Comparison of administrative/billing data to expected protocol-mandated chemotherapy exposure in children with acute myeloid leukemia: A report from the Children's Oncology Group

BACKGROUND

Recently investigators have used analysis of administrative/billing datasets to answer clinical and pharmacoepidemiology questions in pediatric oncology. However, the accuracy of pharmacy data from administrative/billing datasets have not yet been evaluated. The primary objective of this study was to determine the concordance of Pediatric Health Information System (PHIS) administrative/billing chemotherapy data with Children's Oncology Group (COG) protocol-mandated chemotherapy and to assess the implications of this level of concordance for further PHIS research.

PROCEDURE

Data from 384 pediatric patients (1,060 courses of chemotherapy) with acute myeloid leukemia treated on COG clinical trial AAML0531 were previously merged with PHIS data. PHIS chemotherapy administrative/billing data were reviewed for the first three courses of chemotherapy. Accuracy was assessed using three metrics: recognizability of chemotherapy pattern by course, chemotherapy administration pattern by individual medication, and concordance with the number of days of protocol-defined chemotherapy.

RESULTS

The chemotherapy pattern was recognizable in 87.3% of courses when course-wide accuracy was assessed. Chemotherapy administration pattern varied by medication. Cytarabine had perfect concordance 70.9% of the time, daunorubicin had perfect concordance 77.4% of the time, and etoposide had perfect concordance 67.8% of the time.

CONCLUSIONS

The accuracy of chemotherapy administrative/billing data supports the continued use of PHIS data for epidemiology studies as long as investigators perform data quality control checks and evaluate each specific medication prior to undertaking definitive analyses.

Concordance of copy number alterations using a common analytic pipeline for genome-wide analysis of Illumina and Affymetrix genotyping data: a report from the Children's Oncology Group

Copy number alterations (CNAs) are a hallmark of pediatric cancer genomes. An increasing number of research groups use multiple platforms and software packages to detect and analyze CNAs. However, different platforms have experimental and analysis-specific biases that may yield different results. We sought to estimate the concordance of CNAs in children with de novo acute myeloid leukemia between two experimental platforms: Affymetrix SNP 6.0 array and Illumina OmniQuad 2.5 BeadChip. Forty-five paired tumor-remission samples were genotyped on both platforms, and CNAs were estimated from total signal intensity and allelic contrast values using the allele-specific copy number analysis of tumors (ASCAT) algorithm. The two platforms were comparable in detection of CNAs, each missing only two segments from a total of 42 CNAs (4.6%). Overall, there was an interplatform agreement of 96% for allele-specific tumor profiles. However, poor quality samples with low signal/noise ratios showed a high rate of false-positive segments independent of the genotyping platform. These results demonstrate that a common analytic pipeline can be utilized for SNP array data from these two platforms. The customized programming template for the preprocessing, data integration, and analysis is publicly available at https://github.com/AplenCHOP/affyLumCNA.

Phase II/III trial of a pre-transplant farnesyl transferase inhibitor in juvenile myelomonocytic leukemia: a report from the Children's Oncology Group

BACKGROUND

Juvenile myelomonocytic leukemia (JMML) is not durably responsive to chemotherapy, and approximately 50% of patients relapse after hematopoietic stem cell transplant (HSCT). Here we report the activity and acute toxicity of the farnesyl transferase inhibitor tipifarnib, the response rate to 13-cis retinoic acid (CRA) in combination with cytoreductive chemotherapy, and survival following HSCT in children with JMML.

PROCEDURE

Eighty-five patients with newly diagnosed JMML were enrolled on AAML0122 between 2001 and 2006. Forty-seven consented to receive tipifarnib in a phase II window before proceeding to a phase III trial of CRA in combination with fludarabine and cytarabine followed by HSCT and maintenance CRA. Thirty-eight patients enrolled only in the phase III trial.

RESULTS

Overall response rate was 51% after tipifarnib and 68% after fludarabine/cytarabine/CRA. Tipifarnib did not increase pre-transplant toxicities. Forty-six percent of the 44 patients who received protocol compliant HSCT relapsed. Five-year overall survival was 55 ± 11% and event-free survival was 41 ± 11%, with no significant difference between patients who did or did not receive tipifarnib.

CONCLUSIONS

Administration of tipifarnib in the window setting followed by HSCT in patients with newly diagnosed JMML was safe and yielded a 51% initial response rate as a single agent, but failed to reduce relapse rates or improve long-term overall survival.

Multimerin-1 (MMRN1) as Novel Adverse Marker in Pediatric Acute Myeloid Leukemia: A Report from the Children's Oncology Group

PURPOSE

Exploratory gene expression array analyses suggested multimerin-1 (MMRN1) to be a predictive biomarker in acute myelogenous leukemia (AML). Following up on these studies, we evaluated the role of MMRN1 expression as outcome predictor in two recent Children's Oncology Group trials.

EXPERIMENTAL DESIGN

We retrospectively quantified MMRN1 expression in 183 participants of AAML03P1 and 750 participants of AAML0531 by reverse-transcriptase PCR and correlated expression levels with disease characteristics and clinical outcome.

RESULTS

In AAML03P1, the highest quartile of MMRN1 expression (expression ≥0.5 relative to β-glucuronidase; n = 45) was associated with inferior event-free survival (EFS; P < 0.002) and higher relapse risk (P < 0.004). In AAML0531, in which we quantified MMRN1 mRNA for validation, patients with relative MMRN1 expression ≥0.5 (n = 160) less likely achieved remission (67% vs. 77%, P = 0.006), and more frequently had minimal residual disease (43% vs. 24%, P = 0.001) after one induction course. They had inferior overall survival (OS; 44% ± 9% vs. 69% ± 4% at 5 years; P < 0.001) and EFS (32% ± 8% vs. 54% ± 4% at 5 years; P < 0.001) and higher relapse risk (57% ± 10% vs. 35% ± 5% at 5 years; P < 0.001). These differences were partly attributable to the fact that patients with high MMRN1 expression less likely had cytogenetic/molecular low-risk disease (P < 0.001) than those with low MMRN1 expression. Nevertheless, after multivariable adjustment, high MMRN1 expression remained statistically significantly associated with shorter OS (HR, 1.57; 95% confidence interval, 1.17-2.12; P = 0.003) and EFS (HR, 1.34; 1.04-1.73; P = 0.025), and higher relapse risk (HR, 1.40; 1.01-1.94; P = 0.044).

CONCLUSIONS

Together, our studies identify MMRN1 expression as a novel biomarker that may refine AML risk stratification.

Gemtuzumab ozogamicin in children and adolescents with de novo acute myeloid leukemia improves event-free survival by reducing relapse risk: results from the randomized phase III Children’s Oncology Group trial AAML0531

PURPOSE

To improve survival rates in children with acute myeloid leukemia (AML), we evaluated gemtuzumab-ozogamicin (GO), a humanized immunoconjugate targeted against CD33, as an alternative to further chemotherapy dose escalation. Our primary objective was to determine whether adding GO to standard chemotherapy improved event-free survival (EFS) and overall survival (OS) in children with newly diagnosed AML. Our secondary objectives examined outcomes by risk group and method of intensification.

PATIENTS AND METHODS

Children, adolescents, and young adults ages 0 to 29 years with newly diagnosed AML were enrolled onto Children’s Oncology Group trial AAML0531 and then were randomly assigned to either standard five-course chemotherapy alone or to the same chemotherapy with two doses of GO (3 mg/m2/dose) administered once in induction course 1 and once in intensification course 2 (two of three).

RESULTS

There were 1,022 evaluable patients enrolled. GO significantly improved EFS (3 years: 53.1% v. 46.9%; hazard ratio [HzR], 0.83; 95% CI, 0.70 to 0.99; P.04) but not OS (3 years: 69.4% v. 65.4%; HzR, 0.91; 95% CI, 0.74 to 1.13; P = .39). Although remission was not improved (88% v. 85%; P = .15), posthoc analyses found relapse risk (RR) was significantly reduced among GO recipients overall (3 years: 32.8% v. 41.3%; HzR, 0.73; 95% CI, 0.58 to 0.91; P = .006). Despite an increased postremission toxic mortality (3 years: 6.6% v. 4.1%; HzR, 1.69; 95% CI, 0.93 to 3.08; P = .09), disease-free survival was better among GO recipients (3 years: 60.6% v. 54.7%; HzR, 0.82; 95% CI, 0.67 to 1.02; P = .07).

CONCLUSION

GO added to chemotherapy improved EFS through a reduction in RR for children and adolescents with AML.

A Phase 2 study of bortezomib combined with either idarubicin/cytarabine or cytarabine/etoposide in children with relapsed, refractory or secondary acute myeloid leukemia: a report from the Children's Oncology Group

BACKGROUND

This Phase 2 study tested the tolerability and efficacy of bortezomib combined with reinduction chemotherapy for pediatric patients with relapsed, refractory or secondary acute myeloid leukemia (AML). Correlative studies measured putative AML leukemia initiating cells (AML-LIC) before and after treatment.

PROCEDURE

Patients with <400 mg/m(2) prior anthracycline received bortezomib combined with idarubicin (12 mg/m(2) days 1-3) and low-dose cytarabine (100 mg/m(2) days 1-7) (Arm A). Patients with ≥400 mg/m(2) prior anthracycline received bortezomib with etoposide (100 mg/m(2) on days 1-5) and high-dose cytarabine (1 g/m(2) every 12 hours for 10 doses) (Arm B).

RESULTS

Forty-six patients were treated with 58 bortezomib-containing cycles. The dose finding phase of Arm B established the recommended Phase 2 dose of bortezomib at 1.3 mg/m(2) on days 1, 4, and 8 with Arm B chemotherapy. Both arms were closed after failure to meet predetermined efficacy thresholds during the first stage of the two-stage design. The complete response (CR + CRp) rates were 29% for Arm A and 43% for Arm B. Counting additional CRi responses (CR with incomplete neutrophil recovery), the overall CR rates were 57% for Arm A and 48% for Arm B. The 2-year overall survival (OS) was 39 ± 15%. Correlative studies showed that LIC depletion after the first cycle was associated with clinical response.

CONCLUSION

Bortezomib is tolerable when added to chemotherapy regimens for relapsed pediatric AML, but the regimens did not exceed preset minimum response criteria to allow continued accrual. This study also suggests that AML-LIC depletion has prognostic value.

AAML0523: a report from the Children's Oncology Group on the efficacy of clofarabine in combination with cytarabine in pediatric patients with recurrent acute myeloid leukemia

BACKGROUND

The discovery of new, effective non-anthracycline-based reinduction regimens for children with recurrent acute myeloid leukemia (AML) is critical. In this phase 1/2 study, the tolerability and overall response rate of clofarabine in combination with cytarabine was investigated in children with recurrent/refractory AML.

METHODS

AAML0523 enrolled 49 children with AML in first recurrence or who were refractory to induction therapy. The study consisted of a dose-finding phase (9 patients) and an efficacy phase (40 patients). Two children received clofarabine at a dose of 40 mg/m(2)/day and 47 children at a dose of 52 mg/m(2)/day.

RESULTS

Toxicities typical for intensive chemotherapy regimens were observed at all doses of clofarabine. The recommended pediatric phase 2 dose of clofarabine in combination with cytarabine was 52 mg/m(2)/day for 5 days. Of 48 evaluable patients, the overall response rate (complete remission plus complete remission with partial platelet recovery) was 48%. Four patients met conventional criteria for complete remission with incomplete count recovery. Twenty-one of 23 responders subsequently underwent hematopoietic stem cell transplantation. The overall survival rate at 3 years was 46% for responders compared with 16% for nonresponders (P < .001). Patients found to have no minimal residual disease at the end of the first cycle by flow cytometric analysis had superior overall survival after 1 year (100% vs 38%; P = .01).

CONCLUSIONS

The combination of clofarabine and cytarabine yielded an acceptable response rate without excess toxicity in children with recurrent AML. The nearly 50% survival rate reported in responders is highly encouraging in these high-risk patients and suggests that this combination is an effective bridge to hematopoietic stem cell transplantation.

BIRC5 (survivin) splice variant expression correlates with refractory disease and poor outcome in pediatric acute myeloid leukemia: a report from the Children's Oncology Group

BACKGROUND

The inhibitor-of-apoptosis protein survivin, encoded by BIRC5, regulates apoptosis, cell division and proliferation. Several survivin splice variants have been described however, the prognostic significance of their expression has not been well defined in pediatric acute myeloid leukemia (AML).

PROCEDURE

Quantitative expression analyses of BIRC5 mRNA (n = 306) and survivin transcript splice variants (n = 90) were performed on diagnostic bone marrow samples from children with de novo AML treated on the clinical trials CCG-2961 and AAML03P1, then correlated with disease characteristics and clinical outcome.

RESULTS

Total BIRC5 expression did not correlate with clinical outcome. Fragment length analysis and sequencing of the entire BIRC5 transcript demonstrated three splice variants. The most prominent product, wild-type survivin, was expressed in all samples tested. Two minor transcripts were present in 90 patients treated on CCG-2961; survivin-2B and a novel variant, survivin-ΔEx2, characterized by deletion of BIRC5 exon II. A high 2B/ΔEx2 expression ratio (≥1) correlated with increased diagnostic WBC count, monocytic phenotype, +8 cytogenetics, lower complete remission (45% [n = 10] vs. 88% [n = 59], P < 0.001) and higher induction failure rates (23% [n = 5] vs. 3% [n = 2], P = 0.009). Consistent with this poor induction response, patients with a 2B/ΔEx2 ratio ≥1 had inferior 5-year survival rates (OS 36% vs. 60%, P = 0.011; EFS 23% vs. 53% at 5 years, P = 0.001) and appear to have increased relapse risk (P = 0.056). Subset analyses suggest that relative over-expression of 2B, rather than under-expression of ΔEx2 determines clinical response.

CONCLUSIONS

High survivin-2B/ΔEx2 ratios are associated with refractory disease and inferior survival in childhood AML. Survivin splice variant expression warrants prospective evaluation in clinical trials.

Acute myeloid leukaemia (AML) with t(6;9)(p23;q34) is associated with poor outcome in childhood AML regardless of FLT3-ITD status: a report from the Children's Oncology Group

Acute myeloid leukaemia (AML) with t(6;9)(p23;q34) is a rare subtype associated with FLT3-internal tandem duplication (ITD) and poor outcomes. The clinical outcomes of paediatric patients with t(6;9) with and without FLT3-ITD treated on six consecutive cooperative trails were evaluated. In contrast to patients without t(6;9), those with t(6;9) had a significantly lower complete remission rate, higher relapse rate (RR), and poor overall survival (OS). Within t(6;9) patients, those with and without FLT3-ITD had an OS of 40% and 27% respectively (P > 0·9), demonstrating that t(6;9) is a high-risk cytogenetic feature in paediatric AML and its clinical impact is independent of the presence of FLT3-ITD.

High expression of suppressor of cytokine signaling-2 predicts poor outcome in pediatric acute myeloid leukemia: a report from the Children's Oncology Group

Deregulated cytokine signaling is a characteristic feature of acute myeloid leukemia (AML), and expression signatures of cytokines and chemokines have been identified as a significant prognostic factor in this disease. Given this aberrant signaling, we hypothesized that expression of suppressor of cytokine signaling-2 (SOCS2), a negative regulator of cytokine signaling, might be altered in AML and could provide predictive information. Among 188 participants of the Children's Oncology Group AAML03P1 trial, SOCS2 mRNA levels varied > 6000-fold. Higher (> median) SOCS2 expression was associated with inferior overall (60 ± 10% vs. 75 ± 9%, p = 0.026) and event-free (44 ± 10% vs. 59 ± 10%, p = 0.031) survival. However, these differences were accounted for by higher prevalence of high-risk and lower prevalence of low-risk disease among patients with higher SOCS2 expression, limiting the clinical utility of SOCS2 as a predictive marker. It remains untested whether high SOCS2 expression identifies a subset of leukemias with deregulated cytokine signaling that could be amenable to therapeutic intervention.

Comparable survival for pediatric acute myeloid leukemia with poor-risk cytogenetics following chemotherapy, matched related donor, or unrelated donor transplantation

BACKGROUND

We sought to better define the role of hematopoietic cell transplantation (HCT) in first remission (CR1) for high-risk pediatric acute myeloid leukemia (AML).

PROCEDURES

Outcomes were compared among patients aged less than 21 years with cytogenetically defined poor-risk AML treated with chemotherapy, matched related (MRD), or unrelated donor (URD) transplantation in CR1. Poor-risk cytogenetics was defined as monosomy 7/del7q, monosomy 5/del 5q, abnormalities of 3q, t(6;9)(p23;q34), or complex karyotype. Included are patients treated on Children's Oncology Group trials or reported to the Center for International Blood and Marrow Transplant Research from 1989 to 2006.

RESULTS

Of the 233 patients, 123 received chemotherapy, 55 received MRD HCT, and 55 received URD HCT. The 5-year overall survival from the time of consolidation chemotherapy or transplant conditioning was similar: chemotherapy (43% ± 9%), MRD (46% ± 14%), or URD (50% ± 14%), P = 0.99. Similarly, multivariate analysis demonstrated no significant differences in survival [(reference group = chemotherapy); MRD HR 1.08, P = 0.76; URD HR 1.13, P = 0.67] despite lower relapse risk with URD HCT (HR = 0.43, P = 0.01).

CONCLUSIONS

Our findings do not provide support for the preferential use of HCT over chemotherapy alone for children with cytogenetically defined poor-risk AML in CR1.

The prognostic effect of high diagnostic WT1 gene expression in pediatric AML depends on WT1 SNP rs16754 status: report from the Children's Oncology Group

BACKGROUND

WT1 is aberrantly over-expressed in most cases of AML. We recently demonstrated that WT1 SNP rs16754 correlates with favorable outcome and high diagnostic WT1 expression in childhood AML. We examined the clinical correlates of diagnostic WT1 expression within a contemporary COG trial and determined whether its prognostic impact differs between SNP+ and SNP- patients.

PROCEDURE

WT1 mRNA expression was measured via qRT-PCR in diagnostic specimens obtained from 225 patients enrolled on COG-AAML03P1. Direct sequencing of WT1 exon 7 was performed to determine SNP rs16754 genotype. WT1 expression was correlated with disease characteristics, SNP status, and outcome.

RESULTS

Patients were categorized into four groups (quartiles: Q1 through Q4) based on diagnostic WT1 expression for analysis. FLT3/ITD (P = 0.017) and WT1 mutations (P < 0.001) both occurred more frequently in patients with the highest WT1 expression. SNP rs16754 frequency did not vary significantly among the quartiles. When all patients were considered, survival outcomes were similar between quartiles. However, when only SNP- patients (n = 150) were analyzed, those with highest WT1 expression (Q4) had the poorest OS (51% vs. 72% for Q1-Q3, P = 0.006) and EFS (35% vs. 54% for Q1-Q3, P = 0.031). Among SNP+ patients (n = 75), survival did not vary significantly between WT1 expression quartiles.

CONCLUSION

Although WT1 expression was not prognostic when all patients were considered together, stratifying patients by SNP rs16754 genotype revealed significant differences in outcome. In SNP- patients, high WT1 expression predicted decreased survival in univariate, but not multivariate, analysis, due to a preponderance of high-risk cyto/molecular abnormalities in the highest expression quartile.

Outcome of pediatric patients with acute myeloid leukemia (AML) and -5/5q- abnormalities from five pediatric AML treatment protocols: a report from the Children's Oncology Group

BACKGROUND

Abnormalities of chromosome 5q (-5/5q-) are associated with poor prognosis in adults with acute myeloid leukemia (AML). However, there are no large studies on outcomes of children with -5/5q- AML. To determine the disease correlates of this group, we retrospectively analyzed cytogenetic data from five studies of childhood AML.

PROCEDURE

Data from patients whose cytogenetic clones included -5/5q-, with the exception of those with acute promyelocytic leukemia or Down syndrome, were included.

RESULTS

Of the 2,240 patients with cytogenetic data available, 26 (1.2%) had -5 or 5q-. A significant number of these patients were age 11-21 (61.5%, P = 0.031) and had M0 morphology compared with patients without -5/5q- (24.0% vs. 2.8%, P < 0.001). Twenty-two of the 26 patients had a complete remission (CR) response to induction chemotherapy. The 5-year overall survival (OS) from the time of diagnosis for the -5/5q- patients was significantly lower than for patients without -5/5q- (27 ± 17% vs. 50 ± 2%, P = 0.027). Similarly, from induction CR, patients with -5/5q- had significantly worse disease free survival, OS and relapse risk than those without this abnormality (27 ± 19% vs. 46 ± 2%, P = 0.035, 32 ± 20% vs. 57 ± 2%, P = 0.025, 68 ± 21% vs. 45 ± 2%, P = 0.01, respectively).

CONCLUSIONS

Pediatric patients with AML and -5/5q- had a very poor outcome. These findings support the need for new or novel therapies for these patients.

Differences in outcomes of newly diagnosed acute myeloid leukemia for adolescent/young adult and younger patients: a report from the Children's Oncology Group

BACKGROUND

Studies comparing survival of adolescent and young adult (AYA) patients to that of younger patients with newly diagnosed acute myeloid leukemia (AML) have yielded conflicting results. In order to more accurately characterize relative survival and other outcomes of AYA patients, a cross-study analysis was conducted using data from recent trials conducted by the Children's Cancer Group (CCG) and Children's Oncology Group (COG).

METHODS

Data were combined from the CCG-2891, CCG-2941, CCG-2961, and AAML03P1 trials. The data set included 1840 patients, comprising 238 AYA and 1602 younger patients.

RESULTS

Overall survival was not significantly different in the 2 groups (AYA, 49% ± 7% versus younger, 54% ± 3% (± 2 standard errors), P = .058). Relapse was lower in AYA patients (30% ± 7% versus 41% ± 3%, P = .002), but treatment-related mortality (TRM) was higher (25% ± 6% versus 12% ± 2%, P < .001). After adjustment for other factors, older age remained strongly associated with TRM (hazard ratio = 2.30, 95% CI = 1.59-3.33, P < .001). Infection accounted for the excess TRM in AYA patients.

CONCLUSIONS

Survival in AYA and younger patients with newly diagnosed AML is similar; however, older patients are at higher risk for TRM. More effective strategies for preventing mortality from infection in AYA patients are needed.

Outcome of adolescents and young adults with acute myeloid leukemia treated on COG trials compared to CALGB and SWOG trials

BACKGROUND

A retrospective meta-analysis of adolescents and young adults (AYAs) with acute myeloid leukemia (AML) was performed to determine if differences in outcome exist following treatment on pediatric versus adult oncology treatment regimens.

METHODS

Outcomes were compared of 517 AYAs with AML aged 16 to 21 years who were treated on Children's Oncology Group (COG), Cancer and Leukemia Group B (CALGB), and Southwest Oncology Group (SWOG) frontline AML trials from 1986 to 2008.

RESULTS

There was a significant age difference between AYA cohorts in the COG, CALGB, and SWOG trials (median, 17.2 versus 20.1 versus 19.8 years, P < .001). The 10-year event-free survival of the COG cohort was superior to the combined adult cohorts (38% ± 6% versus 23% ± 6%, log-rank P = .006) as was overall survival (45% ± 6% versus 34% ± 7%), with a 10-year estimate comparison of P = .026. However, the younger age of the COG cohort is confounding, with all patients aged 16 to 18 years doing better than those aged 19 to 21 years. Although the 10-year relapse rate was lower for the COG patients (29% ± 6% versus 57% ± 8%, Gray's P < .001), this was offset by a higher postremission treatment-related mortality of 26% ± 6% versus 12% ± 6% (Gray's P < .001). Significant improvements in 10-year event-free survival and overall survival were observed for the entire cohort in later studies.

CONCLUSIONS

Patients treated on pediatric trials had better outcomes than those treated on adult trials, but age is a major confounding variable, making it difficult to compare outcomes by cooperative group.

Significance of expression of ITGA5 and its splice variants in acute myeloid leukemia: a report from the Children's Oncology Group

Acute myeloid leukemia (AML) encompasses a heterogeneous group of diseases, and novel biomarkers for risk refinement and stratification are needed to optimize patient care. To identify novel risk factors, we performed transcriptome sequencing on 68 diagnostic AML samples and identified 2 transcript variants (-E2 and -E2/3) of the α-subunit (ITGA5) of the very late antigen-5 integrin. We then quantified expression of ITGA5 and these splice variants in specimens from participants of the AAML03P1 trial. We found no association between ITGA5 expression and clinical outcome. In contrast, patients with the highest relative expression (Q4) of the -E2/3 ITGA5 splice variant less likely had low-risk disease than Q1-3 patients (21% vs. 38%, P = 0.027). Q4 patients had worse response to chemotherapy with a higher proportion having persistent minimal residual disease (50% vs. 23%, P = 0.003) and inferior overall survival (at 5 years: 48% vs. 67%, P = 0.015); the latter association was limited to low-risk patients (Q4 vs. Q1-3: 56% vs. 85%, P = 0.043) and was not seen in standard-risk (51% vs. 60%, P = 0.340) or high-risk (33% vs. 38%, P = 0.952) patients. Our exploratory studies indicate that transcriptome sequencing is useful for biomarker discovery, as exemplified by the identification of ITGA5 -E2/3 splice variant as potential novel adverse prognostic marker for low-risk AML that, if confirmed, could serve to further risk-stratify this patient subset.

High EVI1 expression is associated with MLL rearrangements and predicts decreased survival in paediatric acute myeloid leukaemia: a report from the children's oncology group

Ectopic viral integration site-1 (EVI1) is highly expressed in certain cytogenetic subsets of adult acute myeloid leukaemia (AML), and has been associated with inferior survival. We sought to examine the clinical and biological associations of EVI1(high) , defined as expression in excess of normal controls, in paediatric AML. EVI1 mRNA expression was measured via quantitative real-time polymerase chain reaction in diagnostic specimens obtained from 206 patients. Expression levels were correlated with clinical features and outcome. EVI1(high) was present in 58/206 (28%) patients. MLL rearrangements occurred in 40% of EVI1(high) patients as opposed to 12% of the EVI1(low/absent) patients (P < 0·001). No abnormalities of 3q26 were found in EVI1(high) patients by conventional cytogenetic analysis, nor were cryptic 3q26 abnormalities detected in a subset of patients screened by next-generation sequencing. French-American-British class M7 was enriched in the EVI1(high) group, accounting for 24% of these patients. EVI1(high) patients had significantly lower 5-year overall survival from study entry (51% vs. 68%, P = 0·015). However, in multivariate analysis including other established prognostic markers, EVI1 expression did not retain independent prognostic significance. EVI1 expression is currently being studied in a larger cohort of patients enrolled on subsequent Children's Oncology Group trials, to determine if EVI1(high) has prognostic value in MLL-rearranged or intermediate-risk subsets.

Clinical significance of CD33 nonsynonymous single-nucleotide polymorphisms in pediatric patients with acute myeloid leukemia treated with gemtuzumab-ozogamicin-containing chemotherapy

PURPOSE

The purpose of this study was to evaluate clinical implications of CD33 single-nucleotide polymorphisms (SNP) in pediatric patients with acute myeloid leukemia (AML) treated with gemtuzumab-ozogamicin (GO)-based therapy.

EXPERIMENTAL DESIGN

We genotyped four CD33 SNPs: rs35112940 (G>A; Arg304Gly), rs12459419 (C>T; Ala14Val), rs2455069 (A>G; Arg69Gly), and rs1803254 (G>C; 3'UTR) in pediatric patients undergoing induction chemotherapy containing GO (COG-AAML03P1 trial; n = 242) or not containing GO (St. Jude AML02 trial; n = 172).

RESULTS

CD33 SNPs were correlated significantly with clinical characteristics and treatment outcome. The coding SNPs, rs35112940 and rs12459419, were significantly associated with clinical endpoints in COG-AAML03P1 but not in the St. Jude AML02 trial. Specifically, among white patients in COG-AAML03P1, the 3-year overall survival (OS) rate from remission was 84% ± 8% for those homozygous (GG) for rs35112940 versus 68% ± 15% for the other genotypes (P = 0.018); these patients also had a lower relapse risk and superior disease-free survival. Likewise, patients homozygous for variant allele (TT) for rs12459419 were more likely to have favorable risk disease than CC and CT genotypes (52% vs. 31%, P = 0.034) and significantly lower diagnostic blast CD33 expression than other genotypes (P < 0.001).

CONCLUSION

Our data suggest that genetic variations in CD33 could impact clinical outcome of GO-based therapy in pediatric AMLs.