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.

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.

Clinical significance of in vivo cytarabine-induced gene expression signature in AML

Despite initial remission, ∼60-70% of adult and 30% of pediatric patients experience relapse or refractory AML. Studies so far have identified base line gene expression profiles of pathogenic and prognostic significance in AML; however, the extent of change in gene expression post-initiation of treatment has not been investigated. Exposure of leukemic cells to chemotherapeutic agents such as cytarabine, a mainstay of AML chemotherapy, can trigger adaptive response by influencing leukemic cell transcriptome and, hence, development of resistance or refractory disease. It is, however, challenging to perform such a study due to lack of availability of specimens post-drug treatment. The primary objective of this study was to identify in vivo cytarabine-induced changes in leukemia cell transcriptome and to evaluate their impact on clinical outcome. The results highlight genes relevant to cytarabine resistance and support the concept of targeting cytarabine-induced genes as a means of improving response.

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.

Outcomes of children with BCR-ABL1–like acute lymphoblastic leukemia treated with risk-directed therapy based on the levels of minimal residual disease

PURPOSE

BCR-ABL1–like acute lymphoblastic leukemia (ALL) is a recently identified B-cell ALL (B-ALL)subtype with poor outcome that exhibits a gene expression profile similar to BCR-ABL1-positive ALL but lacks the BCR-ABL1 fusion protein. We examined the outcome of children with BCR-ABL1–like ALL treated with risk-directed therapy based on minimal residual disease (MRD) levels during remission induction.

PATIENTS AND METHODS

Among 422 patients with B-ALL enrolled onto the Total Therapy XV study between 2000 and 2007, 344 had adequate samples for gene expression profiling. Next-generation sequencing and/or analysis of genes known to be altered in B-ALL were performed in patients with BCR-ABL1–likeALL who had available material. Outcome was compared between patients with and those without BCR-ABL1–like ALL.

RESULTS

Forty (11.6%) of the 344 patients had BCR-ABL1–like ALL. They were significantly more likely to be male, have Down syndrome, and have higher MRD levels on day 19 and at the end of induction than did other patients with B-ALL. Among 25 patients comprehensively studied for genetic abnormalities, 11 harbored a genomic rearrangement of CRLF2, six had fusion transcripts responsive to ABL tyrosine kinase inhibitors or JAK inhibitors, and seven had mutations involving the Ras signaling pathway. There were no significant differences in event-free survival (90.0% +/- 4.7% [SE] v. 88.4% +/- .9% at 5 years; P = .41or in overall survival (92.5% +/- 4.2% v. 95.1% +/- 1.3% at 5 years; P = .41) between patients with and without BCR-ABL1–like ALL.

CONCLUSION

Patients who have BCR-ABL1–like ALL with poor initial treatment response can be salvaged with MRD-based risk-directed therapy and may benefit from identification of kinase-activating lesions for targeted therapies.

Prognostic factors in children with acute myeloid leukaemia and excellent response to remission induction therapy

Minimal residual disease (MRD) is a strong prognostic factor in children and adolescents with acute myeloid leukaemia (AML) but nearly one-quarter of patients who achieve MRD-negative status still relapse. The adverse prognostic factors among MRD-negative patients remain unknown. We analysed the AML02 study cohort to identify demographic and genetic prognostic factors. Among the presenting features, certain 11q23 abnormalities, such as t(6;11) and t(10;11), acute megakaryoblastic leukaemia without the t(1;22), and age ≥10 years were associated with inferior outcome in patients who had MRD-negative status after either remission induction I or II. By contrast, those with rearrangement of CBF genes had superior outcome. Our study identifies patient populations for whom close post-remission MRD monitoring to detect and treat emerging relapse and adjustment in treatment intensity might be indicated.

t(6;9)(p22;q34)/DEK-NUP214-rearranged pediatric myeloid leukemia: an international study of 62 patients

Acute myeloid leukemia with t(6;9)(p22;q34) is listed as a distinct entity in the 2008 World Health Organization classification, but little is known about the clinical implications of t(6;9)-positive myeloid leukemia in children. This international multicenter study presents the clinical and genetic characteristics of 62 pediatric patients with t(6;9)/DEK-NUP214-rearranged myeloid leukemia; 54 diagnosed as having acute myeloid leukemia, representing <1% of all childhood acute myeloid leukemia, and eight as having myelodysplastic syndrome. The t(6;9)/DEK-NUP214 was associated with relatively late onset (median age 10.4 years), male predominance (sex ratio 1.7), French-American-British M2 classification (54%), myelodysplasia (100%), and FLT3-ITD (42%). Outcome was substantially better than previously reported with a 5-year event-free survival of 32%, 5-year overall survival of 53%, and a 5-year cumulative incidence of relapse of 57%. Hematopoietic stem cell transplantation in first complete remission improved the 5-year event-free survival compared with chemotherapy alone (68% versus 18%; P<0.01) but not the overall survival (68% versus 54%; P=0.48). The presence of FLT3-ITD had a non-significant negative effect on 5-year overall survival compared with non-mutated cases (22% versus 62%; P=0.13). Gene expression profiling showed a unique signature characterized by significantly higher expression of EYA3, SESN1, PRDM2/RIZ, and HIST2H4 genes. In conclusion, t(6;9)/DEK-NUP214 represents a unique subtype of acute myeloid leukemia with a high risk of relapse, high frequency of FLT3-ITD, and a specific gene expression signature.

A revised definition for cure of childhood acute lymphoblastic leukemia

With improved contemporary therapy, we re-assess long-term outcome in patients completing treatment for childhood acute lymphoblastic leukemia to determine when cure can be declared with a high degree of confidence. In 6 successive clinical trials between 1984 and 2007, 1291(84.5%) patients completed all therapy in continuous complete remission. The post-therapy cumulative risk of relapse or development of a second neoplasm and the event-free survival rate and overall survival were analyzed according to the presenting features and the three treatment periods defined by relative outcome. Over the three treatment periods, there has been progressive increase in the rate of event-free survival (65.2% vs. 74.8% vs. 85.1% [P<0.001]) and overall survival (76.5% vs. 81.1% vs. 91.7% [P<0.001]) at 10 years. The most important predictor of outcome after completion of therapy was the type of treatment. In the most recent treatment period, which omitted the use of prophylactic cranial irradiation, the post-treatment cumulative risk of relapse was 6.4%, death in remission 1.5%, and development of a second neoplasm 2.3% at 10 years, with all relapses except one occurring within 4 years off therapy. None of the 106 patients with the t(9;22)/BCR-ABL1, t(1;19)/TCF3-PBX1 or t(4;11)/MLL-AFF1 had relapsed after 2 years from completion of therapy. These findings demonstrate that with contemporary effective therapy that excludes cranial irradiation, approximately 6% of children with acute lymphoblastic leukemia may relapse after completion of treatment, and those who remain in remission at 4 years post-treatment may be considered cured (i.e., less than 1 % chance of relapse).

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.

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.

Nasopharyngeal alveolar rhabdomyosarcoma expressing CD56: a mimicker of extranodal natural killer/T-cell lymphoma

Alveolar rhabdomyosarcoma (ARMS) is remarkably rare in adults older than 45 years. Histologically, the tumor is composed of blue round cells with frequent expression of CD56 in addition to myogenic markers. Recent studies of ARMS have shown two specific recurrent translocations: PAX3-FKHR [t(2;13)(q35;q14)] or PAX7-FKHR [t(1;13)(p36;q14)]. Extranodal natural killer (NK)/T-cell lymphoma (ENKTL) occurs most frequently in the upper aerodigestive tract with a male preference in East Asia and Central and South Americas with neoplastic cells frequently expressing CD56. We report a 53-year-old Taiwanese man presenting with a nasopharyngeal mass, cervical lymphadenopathy, and multiple bone metastases. Histologically, the nasopharyngeal biopsy revealed diffuse sheets of small blue round tumor cells without obvious alveolar pattern, angioinvasion or tumor necrosis. An initial erroneous diagnosis of ENKTL was made due to CD56 expression using fresh tumor tissue with flow cytometric analysis and the patient was treated accordingly. Retrospective study showed that the tumor cells expressed CD56, desmin, and myogenin. Fluorescence in situ hybridization revealed that the tumor cells were positive for FKHR gene rearrangement, confirming the diagnosis of ARMS. Our case illustrates that a diagnosis of ENKTL based solely on CD56 expression can be misleading for a nasopharyngeal small blue round cell tumor. ARMS should be included as a differential diagnosis, and a correct diagnosis can be reached only after a high index of suspicion and a thorough histological examination with the aid of ancillary studies.

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.

McIntosh M, Meshinchi S. 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.

Successful treatment of pediatric plasmacytoid dendritic cell tumors with a contemporary regimen for acute lymphoblastic leukemia

Dendritic cell leukemia (DCL) or hematodermic tumor is an uncommon subtype of acute leukemia. In contrast to adult cases, children tend to have a less aggressive course. The diagnosis of DCL should be considered when its characteristic morphologic features are present and leukemic cells co-express CD4 and CD56. Cases of DCL among pediatric patients have been reported to respond to therapeutic regimens for acute lymphoblastic leukemia, but details regarding the specifics of therapy are lacking.

The genomic landscape of hypodiploid acute lymphoblastic leukemia

The genetic basis of hypodiploid acute lymphoblastic leukemia (ALL), a subtype of ALL characterized by aneuploidy and poor outcome, is unknown. Genomic profiling of 124 hypodiploid ALL cases, including whole-genome and exome sequencing of 40 cases, identified two subtypes that differ in the severity of aneuploidy, transcriptional profiles and submicroscopic genetic alterations. Near-haploid ALL with 24-31 chromosomes harbor alterations targeting receptor tyrosine kinase signaling and Ras signaling (71%) and the lymphoid transcription factor gene IKZF3 (encoding AIOLOS; 13%). In contrast, low-hypodiploid ALL with 32-39 chromosomes are characterized by alterations in TP53 (91.2%) that are commonly present in nontumor cells, IKZF2 (encoding HELIOS; 53%) and RB1 (41%). Both near-haploid and low-hypodiploid leukemic cells show activation of Ras-signaling and phosphoinositide 3-kinase (PI3K)-signaling pathways and are sensitive to PI3K inhibitors, indicating that these drugs should be explored as a new therapeutic strategy for this aggressive form of leukemia.

Comparative analysis of different approaches to measure treatment response in acute myeloid leukemia

PURPOSE

In acute myeloid leukemia (AML), initial treatment response by morphologic analysis of bone marrow predicts long-term outcome. Response can now be assessed by minimal residual disease (MRD) monitoring with flow cytometry or polymerase chain reaction (PCR). We determined the relation among the results of these approaches and their prognostic value.

PATIENTS AND METHODS

In the multicenter AML02 study, follow-up bone marrow samples from 203 children and adolescents with newly diagnosed AML were examined by flow cytometry (n = 1,514), morphology (n = 1,382), and PCR amplification of fusion transcripts (n = 508). Results were correlated with treatment outcome.

RESULTS

Among 1,215 samples with less than 5% leukemic myeloblasts by morphology, 100 (8.2%) were MRD positive (≥ 0.1%) by flow cytometry, whereas 96 (57.5%) of the 167 samples with ≥ 5% blasts were MRD negative. Virtually all (308 of 311; 99.0%) MRD-negative samples by PCR were also MRD negative by flow cytometry. However, only 19 (9.6%) of the 197 PCR-positive samples were flow cytometry positive, with analyses of AML1-ETO and CBFβ-MYH11 accounting for most discrepancies, whereas eight of 13 MLL-positive samples had detectable MRD by flow cytometry. MRD by flow cytometry after induction 1 or 2 predicted lower event-free survival and higher relapse rate (P < .001) and was an independent prognostic factor in a multivariable analysis; prediction was not improved by morphologic information or molecular findings.

CONCLUSION

In childhood AML, morphologic assessment of treatment response has limited value if MRD is measured by flow cytometry. MLL fusion transcripts can provide prognostic information in some patients, whereas monitoring of AML1-ETO and CBFβ-MYH11 transcripts is largely uninformative.

Abstract 4870: Integrated genomic analysis of hypodiploid acute lymphoblastic leukemia

Hypodiploid acute lymphoblastic leukemia (ALL) is an aggressive form of leukemia characterized by multiple whole chromosomal losses and very dismal outcome. Our previous genome wide study of hypodiploid childhood ALL cases treated by the Children's Oncology Group and St Jude, employed interrogation of DNA copy number alterations using Affymetrix SNP 6.0 microarrays, candidate gene resequencing and gene expression profiling using Affymetrix U133 Plus 2.0 microarrays. These analyses showed that this disease can be divided into multiple subtypes characterized by variation in the degree of aneuploidy, distinct submicroscopic deletions, sequence mutations and gene expression profile. Near haploid ALL (24-31 chromosomes) frequently harbors alterations of genes regulating Ras signaling (67.6%; NF1, NRAS, KRAS, PTPN11, FLT3, and PAG1), IKZF3 (encoding the lymphoid transcription factor AIOLOS; 13.2%), and a histone gene cluster at 6p22 (17.6%), while low hypodiploid ALL (32-39 chromosomes) is enriched for IKZF2 (HELIOS; 52.9%), TP53 (70.6%) and RB1 (41.2%) alterations. A striking finding was exclusivity of Ras signaling and IKZF2/3 alterations, and biochemical indications of Ras pathway activation in both near haploid and low hypodiploid ALL. To further interrogate the genomic changes of hypodiploid ALL, we performed next generation sequencing using either Illumina GAIIx or HiSeq3000 sequencers on both tumor and matched remission DNA. Whole genome sequencing to at least 30 fold haploid coverage was performed on 10 near haploid and 8 low hypodiploid cases, and whole exome sequencing (Agilent SureSelect Human All Exon 50Mb) on 5 near haploid and 1 low hypodiploid cases. The burden of single nucleotide variations (SNVs) and insertion/deletion (indel) mutations was in general low in this ALL subtype, with 0-5 indels and 9-95 SNVs in coding regions and untranslated leader regions in the whole genome sequenced cases, where the majority of cases had fewer than 30 SNVs. Further, the number of structural variations, including the ones too small to be identified by SNP microarray analysis, and structural rearrangements, were also low, with less than 25 structural variations identified in the whole genome sequenced cases. For the whole exomes, between 10 and 42 non-silent SNVs and 1-2 indels were identified per case. No recurrent alterations not previously identified in the hypodiploid cohort were found in these 24 cases, indicating that the initial genome wide study of this cohort identified the major recurrent alterations in hypodiploid ALL. However, the recurrence screening including the remaining 78 near haploid and low hypodiploid cases in our cohort on the alterations identified by the whole genome and exome sequencing study is ongoing. Altogether, these findings provide critical new insights into the genetic basis of hypodiploid ALL, and indicate that therapeutic targeting of the Ras pathway should be pursued in this disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4870. doi:1538-7445.AM2012-4870

ETV6-RUNX1-positive childhood acute lymphoblastic leukemia: improved outcome with contemporary therapy

ETV6-RUNX1 fusion is the most common genetic aberration in childhood acute lymphoblastic leukemia (ALL). To evaluate whether outcomes for this drug-sensitive leukemia are improved by contemporary risk-directed therapy, we studied clinical features, response and adverse events of 168 children with newly diagnosed ETV6-RUNX1-positive ALL on St Jude Total Therapy studies XIIIA (N=36), XIIIB (N=38) and XV (N=94). Results were compared with 494 ETV6-RUNX1-negative B-precursor ALL patients. ETV6-RUNX1 was associated with age 1-9 years, pre-treatment classification as low risk and lower levels of minimal residual disease (MRD) on day 19 of therapy (P<0.001). Event-free survival (EFS) or overall survival (OS) did not differ between patients with or without ETV6-RUNX1 in Total XIIIA or XIIIB. By contrast, in Total XV, patients with ETV6-RUNX1 had significantly better EFS (P=0.04; 5-year estimate, 96.8±2.4% versus 88.3±2.5%) and OS (P=0.04; 98.9±1.4% versus 93.7±1.8%) than those without ETV6-RUNX1. Within the ETV6-RUNX1 group, the only significant prognostic factor associated with higher OS was the treatment protocol Total XV (versus XIIIA or XIIIB) (P=0.01). Thus, the MRD-guided treatment schema including intensive asparaginase and high-dose methotrexate in the Total XV study produced significantly better outcomes than previous regimens and demonstrated that nearly all children with ETV6-RUNX1 ALL can be cured.