The t(9;22)(q34;q11) or Philadelphia chromosome creates a BCR–ABL1 fusion gene encoding for a chimeric BCR–ABL1 protein. It is present in 3–4% of pediatric acute lymphoblastic leukemia (Ph+ ALL), and about 25% of adult ALL cases. Prior to the advent of tyrosine kinase inhibitors (TKI), Ph+ ALL was associated with a very poor prognosis despite the use of intensive chemotherapy and frequently hematopoietic stem-cell transplantation (HSCT) in first remission. The development of TKIs revolutionized the therapy of Ph+ ALL. Addition of the first generation ABL1 class TKI imatinib to intensive chemotherapy dramatically increased the survival for children with Ph+ ALL and established that many patients can be cured without HSCT. In parallel, the mechanistic understanding of Ph+ ALL expanded exponentially through careful mapping of pathways downstream of BCR–ABL1, the discovery of mutations in master regulators of B-cell development such as IKZF1 (Ikaros), PAX5, and early B-cell factor (EBF), the recognition of the complex clonal architecture of Ph+ ALL, and the delineation of genomic, epigenetic, and signaling abnormalities contributing to relapse and resistance. Still, many important basic and clinical questions remain unanswered. Current clinical trials are testing second generation TKIs in patients with newly diagnosed Ph+ ALL. Neither the optimal duration of therapy nor the optimal chemotherapy backbone are currently defined. The role of HSCT in first remission and post-transplant TKI therapy also require further study. In addition, it will be crucial to continue to dig deeper into understanding Ph+ ALL at a mechanistic level, and translate findings into complementary targeted approaches. Expanding targeted therapies hold great promise to decrease toxicity and improve survival in this high-risk disease, which provides a paradigm for how targeted therapies can be incorporated into treatment of other high-risk leukemias.
acute lymphoblastic leukemia; BCR–ABL1; tyrosine kinase inhibition; chemotherapy; hematopoietic stem-cell transplantation
Platinum agents have been used for a variety of cancers, including pivotal use in pediatric tumors for many years. Oxaliplatin, a third generation platinum, has a different side effect profile and may provide improved activity in pediatric cancers.
Patients 21 years or younger with progressive or refractory malignant solid tumors, including tumors of the central nervous system were enrolled on this multi-center open label, non-randomized phase 1 dose escalation study. The study used a standard 3+3 dose escalation design with 2 dose levels (85 mg/m2 and 100 mg/m2) with an expansion cohort of 15 additional patients at the recommended dose. Patients received oxaliplatin at the assigned dose level and 5-fluorouracil bolus 400 mg/m2 followed by a 46-hour 5-fluorouracil infusion of 2,400 mg/m2 every 14 days. The leucovorin dose was fixed at 400 mg/m2 for all cohorts.
Thirty-one evaluable patients were enrolled, 8 at 85 mg/m2 and 23 at 100 mg/m2 for a total of 121 courses. The median age was 12 years (range 2–19 years). The main toxicities were hematologic, primarily neutrophils and platelets. The most common non-hematologic toxicities were gastrointestinal. Stable disease was noted in 11 patients (54% of evaluable patients) and 1 confirmed partial response in a patient with osteosarcoma.
The maximum planned dose of oxaliplatin at 100 mg/m2 per dose in combination with 5-fluorouracil and leucovorin was safe and well tolerated and in this patient population. This combination demonstrated modest activity in patients with refractory or relapsed solid tumor and warrants further study.
oxaliplatin; pediatrics; chemotherapy; 5-Fluorouracil; FOLFOX; phase I
The rare translocation t(8;14)(q11.2;q32) has been described in patients with B-cell acute lymphoblastic leukemia (ALL), particularly patients with Down Syndrome (DS).
We describe patients with t(8;14)(q11.2;q32) that were identified by the Children's Oncology Group (COG) ALL cytogenetics database, expanding our previous report of 10 patients with this translocation. Twenty-two such patients were treated with COG protocols. All patients had B-cell ALL and 7 (31.8%) had DS. None of the children with DS had an event, thus these patients had a superior estimated 5-year event-free survival (EFS) compared to non-DS patients (100% vs. 50.1 ± 17.7%; p=0.04). Only one patient (4.5%) had a concomitant Philadelphia chromosome t(9;22)(q34;q11.2). The cytogenetics data of two additional patients, who were not eligible for COG protocols, are also included in this report.
In conclusion, ALL patients with the recurring translocation t(8;14)(q11.2;q32) have B-cell phenotype and a high percentage have DS. Children with DS and t(8;14)(q11.2;q34) have improved event-free survival using standard COG therapy compared to non-DS patients. We did not find an increased number of patients with a concomitant Philadelphia chromosome in this population.
Acute Lymphoblastic Leukemia; B-cell; translocation; Down Syndrome
Relapsed childhood acute lymphoblastic leukemia (ALL) carries a poor prognosis despite intensive retreatment, due to intrinsic drug resistance1-2. The biological pathways that mediate resistance are unknown. Here we report the transcriptome profiles of matched diagnosis and relapse bone marrow specimens from ten pediatric B lymphoblastic leukemia patients using RNA-sequencing. Transcriptome sequencing identified 20 newly acquired novel non-synonymous mutations not present at initial diagnosis, of which two patients harbored relapse specific mutations in the same gene, NT5C2, a 5′-nucleotidase. Full exon sequencing of NT5C2 was completed in 61 additional relapse specimens, identifying five additional cases. Enzymatic analysis of mutant proteins revealed that base substitutions conferred increased enzymatic activity and resistance to treatment with nucleoside analogue therapies. Clinically, all patients who harbored NT5C2 mutations relapsed early, or within 36 months of initial diagnosis (p=0.03). These results suggest that mutations in NT5C2 are associated with the outgrowth of drug resistant clones in ALL.
Children's Oncology Group study AALL00P2 was designed to assess the feasibility and safety of adding nelarabine to a BFM 86–based chemotherapy regimen in children with newly diagnosed T-cell acute lymphoblastic leukemia (T-ALL).
Patients and Methods
In stage one of the study, eight patients with a slow early response (SER) by prednisone poor response (PPR; ≥ 1,000 peripheral blood blasts on day 8 of prednisone prephase) received chemotherapy plus six courses of nelarabine 400 mg/m2 once per day; four patients with SER by high minimal residual disease (MRD; ≥ 1% at day 36 of induction) received chemotherapy plus five courses of nelarabine; 16 patients with a rapid early response (RER) received chemotherapy without nelarabine. In stage two, all patients received six 5-day courses of nelarabine at 650 mg/m2 once per day (10 SER patients [one by MRD, nine by PPR]) or 400 mg/m2 once per day (38 RER patients; 12 SER patients [three by MRD, nine by PPR]).
The only significant difference in toxicities was decreased neutropenic infections in patients treated with nelarabine (42% with v 81% without nelarabine). Five-year event-free survival (EFS) rates were 73% for 11 stage one SER patients and 67% for 22 stage two SER patients treated with nelarabine versus 69% for 16 stage one RER patients treated without nelarabine and 74% for 38 stage two RER patients treated with nelarabine. Five-year EFS for all patients receiving nelarabine (n = 70) was 73% versus 69% for those treated without nelarabine (n = 16).
Addition of nelarabine to a BFM 86–based chemotherapy regimen was well tolerated and produced encouraging results in pediatric patients with T-ALL, particularly those with a SER, who have historically fared poorly.
The FDA is now exerting its regulatory authority over molecular diagnostics and their assays used for medical-decision making in clinical trials by performing pre-Investigational Device Exemption (IDE) reviews in all phases of clinical trials. This review assesses the analytical performance of the assay for the diagnostic and considers how that performance affects the diagnostic and the patient and their risks and benefits from treatment. This manuscript reviews the process of the first review that was performed on a new Children's Oncology Group (COG) Phase III trial in Acute Myelogenous Leukemia. The lessons learned and recommendations for how to prepare for and incorporate this new level of regulatory review into the protocol development process are presented.
The available guidelines for varicella vaccination of susceptible children with acute lymphoblastic leukemia (ALL) have become increasingly conservative. However, vaccination of those who have remained in continuous complete remission for one year and are receiving chemotherapy is still considered a reasonable option. There is little available data to allow a comparison of the risk vs. benefit of vaccinating these patients.
We retrospectively reviewed mortality due to varicella in the records of 15 pediatric ALL study groups throughout Europe, Asia, and North America during the period 1984–2008.
We found that 20 of 35,128 children with ALL (0.057%; 95% confidence interval [CI], 0.037%–0.088%) died of VZV infection. The mortality rate was lower in North America (3 of 11,558 children, 0.026%; 95% CI, 0.009%–0.076%) than in the Asian countries (2 of 4,882 children, 0.041%; 95% CI, 0.011%–0.149%) and in Europe (15 of 18,688 children, 0.080%; 95% CI, 0.049%–0.132%) consistent with the generally higher rate of VZV vaccination in North America. Fourteen of the 20 patients (70%) died during the first year of treatment for ALL. One death was attributed to varicella vaccination.
The negligible rate of fatal varicella infection in children with ALL, the risk that accompanies vaccination, and the necessity of withholding chemotherapy for vaccination appear to outweigh the potential benefit of varicella vaccination for children during treatment of ALL.
varicella zoster virus; pediatric; acute lymphoblastic leukemia; vaccination; immunization; mortality
Failure of remission-induction therapy is a rare but highly adverse event in children and adolescents with acute lymphoblastic leukemia (ALL).
We identified induction failure, defined by the persistence of leukemic blasts in blood, bone marrow, or any extramedullary site after 4 to 6 weeks of remission-induction therapy, in 1041 of 44,017 patients (2.4%) 0 to 18 years of age with newly diagnosed ALL who were treated by a total of 14 cooperative study groups between 1985 and 2000. We analyzed the relationships among disease characteristics, treatments administered, and outcomes in these patients.
Patients with induction failure frequently presented with high-risk features, including older age, high leukocyte count, leukemia with a T-cell phenotype, the Philadelphia chromosome, and 11q23 rearrangement. With a median follow-up period of 8.3 years (range, 1.5 to 22.1), the 10-year survival rate (±SE) was estimated at only 32±1%. An age of 10 years or older, T-cell leukemia, the presence of an 11q23 rearrangement, and 25% or more blasts in the bone marrow at the end of induction therapy were associated with a particularly poor outcome. High hyperdiploidy (a modal chromosome number >50) and an age of 1 to 5 years were associated with a favorable outcome in patients with precursor B-cell leukemia. Allogeneic stem-cell transplantation from matched, related donors was associated with improved outcomes in T-cell leukemia. Children younger than 6 years of age with precursor B-cell leukemia and no adverse genetic features had a 10-year survival rate of 72±5% when treated with chemotherapy only.
Pediatric ALL with induction failure is highly heterogeneous. Patients who have T-cell leukemia appear to have a better outcome with allogeneic stem-cell transplantation than with chemotherapy, whereas patients who have precursor B-cell leukemia without other adverse features appear to have a better outcome with chemotherapy. (Funded by Deutsche Krebshilfe and others.)
Post-transplant lymphoproliferative disorder (PTLD) is the most after SOT (liver and lungs) and review cases reported in the literature. common treatment related malignancy that occurs after solid organ Both patients had a bimodal response to therapy with initial transplantation (SOT). PTLD has extended from its initial description eradication of bulky nodal disease with regimens typically used to as an Epstein–Barr virus (EBV)-driven B-cell proliferation to include treat leukemia, but persistence of low-level clonal T-cells in marrow, EBV-negative and non B-lineage cases. T-cell PTLD (T-PTLD) is rare CSF and lung in one case. Pediatr Blood Cancer 2008;50:415–in both adults and children. We report two cases of pediatric T-PTLD 418.
flow cytometry; T-cell PTLD; T-cell receptor V-beta
Asparaginases are a cornerstone of treatment protocols for acute lymphoblastic leukemia (ALL) and are used for remission induction and intensification treatment in all pediatric regimens and in the majority of adult protocols. Extensive clinical data have shown that intensive asparaginase treatment improves clinical outcomes in childhood ALL. Three asparaginase preparations are available; the native asparaginase derived from Escherichia coli (E. coli-asparaginase), a pegylated form of this enzyme (PEG-asparaginase) and a product isolated from Erwinia chrysanthemi, i.e. Erwinia asparaginase. Clinical hypersensitivity reactions and silent inactivation due to antibodies against E.coli-asparaginase, lead to inactivation of E-Coli asparaginase in up to 60% of cases. Current treatment protocols include E. coli-asparaginase or PEG-asparaginase for first-line treatment of ALL. Typically, patients exhibiting sensitivity to one formulation of asparaginase are switched to another product to ensure they receive the most efficacious treatment regimen possible. Erwinia asparaginase is used as a second- or third-line treatment in European and US protocols. Despite the universal inclusion of asparaginase in such treatment protocols, there is much debate regarding the optimal formulation and dosage of these agents. This manuscript provides an overview of available evidence to make recommendations for optimal use of Erwinia asparaginase in the treatment of ALL.
acute lymphoblastic leukemia; asparagine depletion; asparaginase; Erwinia asparaginase; Erwinase; ALL
In a previous analysis of 326 children with Philadelphia chromosome (Ph) –positive acute lymphoblastic leukemia (ALL) treated between 1986 and 1996, hematopoietic stem-cell transplantation from HLA-matched related donors, but not from unrelated donors, offered a superior outcome than chemotherapy alone. To evaluate the impact of recent improvements in chemotherapy and transplantation, we performed a similar analysis on patients treated in the following decade.
Patients and Methods
We analyzed 610 patients with Ph-positive ALL treated between 1995 and 2005 without tyrosine kinase inhibitor therapy. The median follow-up duration was 6.3 years.
Complete remission was achieved in 89% of patients. The 7-year event-free survival and overall survival rates were superior in the present cohort compared with the previous cohort (32.0% ± 2.0% v 25.0% ± 3.0, respectively, P = .007; and 44.9% ± 2.2% v 36.0% ± 3.0%, respectively, P = .017). Compared with chemotherapy alone, transplantation with matched related donors or unrelated donors in first remission (325 patients) showed an advantage with increasing follow-up, suggesting greater protection against late relapses (hazard ratio at 5 years, 0.37; P < .001). In the multivariate Cox regression analysis accounting for treatment (transplantation v no transplantation), age, leukocyte count, and early response had independent impact on treatment outcome.
Clinical outcome of children and adolescents with Ph-positive ALL has improved with advances in transplantation and chemotherapy. Transplantations with matched related donors and unrelated donors were equivalent and offered better disease control compared with chemotherapy alone. Age, leukocyte count, and early treatment response were independent prognostic indicators. The results of this study will serve as a historical reference to evaluate the therapeutic impact of tyrosine kinase inhibitors on the outcome of Ph-positive ALL.
To identify children with T-cell acute lymphoblastic leukemia (T-ALL) at high risk of induction chemotherapy failure by using DNA copy number analysis of leukemic cells collected at diagnosis.
Patients and Methods
Array comparative genomic hybridization (CGH) was performed on genomic DNA extracted from diagnostic lymphoblasts from 47 children with T-ALL treated on Children's Oncology Group Study P9404 or Dana-Farber Cancer Institute Protocol 00-01. These samples represented nine patients who did not achieve an initial complete remission, 13 who relapsed, and 25 who became long-term, event-free survivors. The findings were confirmed in an independent cohort of patients by quantitative DNA polymerase chain reaction (DNA-PCR), an assay that is well suited for clinical application.
Analysis of the CGH findings in patients in whom induction chemotherapy failed compared with those in whom induction chemotherapy was successful identified the absence of biallelic TCRγ locus deletion (ABD), a characteristic of early thymocyte precursors before V(D)J recombination, as the most robust predictor of induction failure (P < .001). This feature was also associated with markedly inferior event-free (P = .002) and overall survival (P < .001) rates: 25% versus 58% and 25% versus 72%, respectively. Using a rapid and inexpensive quantitative DNA-PCR assay, we validated ABD as a predictor of a poor response to induction chemotherapy in an independent series of patients.
Lymphoblasts from children with T-ALL should be evaluated at diagnosis for deletion within the TCRγ locus. Patients lacking biallelic deletion, which confers a high probability of induction failure with contemporary therapy, should be assigned to alternative therapy in the context of a prospective clinical trial.
One of the challenges of incorporating molecularly targeted drugs into multi-agent chemotherapy (backbone) regimens is defining dose limiting toxicities (DLTs) of the targeted agent against the background of toxicities of the backbone regimen. An international panel of 22 pediatric acute lymphocytic leukemia (ALL) experts addressed this issue (www.ALLNA.org). Two major questions surrounding DLT assessment were explored: 1) how toxicities can be best defined, assessed, and attributed; and 2) how effective dosing of new agents incorporated into multi-agent ALL clinical trials can be safely established in the face of disease- and therapy-related systemic toxicities. The consensus DLT definition incorporates tolerance of resolving Grade 3 and some resolving Grade 4 toxicities with stringent safety monitoring. This functional DLT definition is being tested in two Children’s Oncology Group (COG) ALL clinical trials.
ALL; ALL relapse; developmental therapeutics; dose-limiting toxicity; maximum tolerated dose
Imatinib mesylate is a targeted agent that may be used against Philadelphia chromosome–positive (Ph+) acute lymphoblastic leukemia (ALL), one of the highest risk pediatric ALL groups.
Patients and Methods
We evaluated whether imatinib (340 mg/m2/d) with an intensive chemotherapy regimen improved outcome in children ages 1 to 21 years with Ph+ ALL (N = 92) and compared toxicities to Ph− ALL patients (N = 65) given the same chemotherapy without imatinib. Exposure to imatinib was increased progressively in five patient cohorts that received imatinib from 42 (cohort 1; n = 7) to 280 continuous days (cohort 5; n = 50) before maintenance therapy. Patients with human leukocyte antigen (HLA) –identical sibling donors underwent blood and marrow transplantation (BMT) with imatinib given for 6 months following BMT.
Continuous imatinib exposure improved outcome in cohort 5 patients with a 3-year event-free survival (EFS) of 80% ± 11% (95% CI, 64% to 90%), more than twice historical controls (35% ± 4%; P < .0001). Three-year EFS was similar for patients in cohort 5 treated with chemotherapy plus imatinib (88% ± 11%; 95% CI, 66% to 96%) or sibling donor BMT (57% ± 22%; 95% CI, 30.4% to 76.1%). There were no significant toxicities associated with adding imatinib to intensive chemotherapy. The higher imatinib dosing in cohort 5 appears to improve survival by having an impact on the outcome of children with a higher burden of minimal residual disease after induction.
Imatinib plus intensive chemotherapy improved 3-year EFS in children and adolescents with Ph+ ALL, with no appreciable increase in toxicity. BMT plus imatinib offered no advantage over BMT alone. Additional follow-up is required to determine the impact of this treatment on long-term EFS and determine whether chemotherapy plus imatinib can replace BMT.
Patients 16 to 21 years of age with acute lymphoblastic leukemia (ALL) have an inferior outcome compared with younger children, leading some medical oncologists to advocate allogeneic stem-cell transplantation in first remission for these patients. We examined outcome for young adults with ALL enrolled onto the Children's Cancer Group (CCG) 1961 study between 1996 and 2002.
Patients and Methods
CCG 1961 entered patients with ALL 1 to 21 years of age with initial WBC count ≥ 50,000/μL and/or age ≥ 10 years. Randomly assigned therapies evaluated the impact of postinduction treatment intensification on outcome. We examined outcome and prognostic factors for 262 young adults with ALL.
Five-year event-free and overall survival rates for young adult patients are 71.5% (SE, 3.6%) and 77.5% (SE, 3.3%), respectively. Rapid responder patients (< 25% bone marrow blasts on day 7) randomly assigned to augmented therapy had 5-year event-free survival of 81.8% (SE, 7%), as compared with 66.8% (SE, 6.7%) for patients receiving standard therapy (P = .07). One versus two interim maintenance and delayed intensification courses had no significant impact on event-free survival. WBC count more than 50,000/μL was an adverse prognostic factor.
Young adult patients with ALL showing a rapid response to induction chemotherapy benefit from early intensive postinduction therapy but do not benefit from a second interim maintenance and delayed intensification phase. Given the excellent outcome with this chemotherapy, there seems to be no role for the routine use of allogeneic stem-cell transplantation in first remission for young adults with ALL.
The Children’s Cancer Group enrolled 13,298 young people age < 21 years on one of 16 protocols between 1983 and 2002. Outcomes were examined in three time periods, 1983–1988, 1989–1995, 1996–2002. Over the three intervals, 10-year event-free survival (EFS) for Rome/NCI standard risk and higher risk B-precursor patients was 68% and 58%, 77% and 63%, and 78% and 67%, respectively; while for standard risk and higher risk T-cell patients, EFS was 65% and 56%, 78% and 68%, and 70% and 72%, respectively. Five-year EFS for infants was 36%, 38%, and 43%, respectively. Seminal randomized studies led to a number of important findings. Stronger post induction intensification improved outcome for both standard and higher risk patients. With improved systemic therapy, additional IT methotrexate effectively replaced cranial radiation. For standard risk patients receiving three-drug induction, iso-toxic substitution of dexamethasone for prednisone improved EFS. Pegylated asparaginase safely and effectively replaced native asparaginase. Thus, rational therapy modifications yielded better outcomes for both standard and higher risk patients. These trials provide the platforms for current Children’s Oncology Group trials.
Acute lymphoblastic leukemia; children; randomized clinical trials
Despite great progress in curing childhood acute lymphoblastic leukemia, survival after relapse remains poor. We analyzed survival following relapse among 9,585 pediatric patients enrolled on Children's Oncology Group clinical trials between 1988-2002. A total of 1961 patients (20.5%) experienced relapse at any site. The primary endpoint was survival. Patients were subcategorized by site of relapse and timing of relapse from initial diagnosis. Time to relapse remains the strongest predictor of survival. Patients experiencing early relapse less than 18 months from initial diagnosis had a particularly poor outcome with a 5-year survival estimate of 21.0±1.8%. Standard risk patients who relapsed had improved survival compared to their higher risk counterparts; differences in survival for the two risk groups was most pronounced for patients relapsing after 18 months. Adjusting for both time and relapse site, multivariate analysis showed that age (10+ yrs) and presence of CNS disease at diagnosis, male gender, and T-cell disease were significant predictors of inferior post-relapse survival. Of note, there was no difference in survival rates for relapsed patients in earlier versus later era trials. New therapeutic strategies are urgently needed for children with relapsed ALL and efforts should focus on discovering the biological pathways that mediate drug resistance.
relapsed acute lymphoblastic leukemia; Children's Oncology Group; pediatric
Continuous complete clinical remission in T-cell acute lymphoblastic leukemia (T-ALL) is now approaching 80% due to the implementation of aggressive chemotherapy protocols but patients that relapse continue to have a poor prognosis. Such patients could benefit from augmented therapy if their clinical outcome could be more accurately predicted at the time of diagnosis. Gene expression profiling offers the potential to identify additional prognostic markers but has had limited success in generating robust signatures that predict outcome across multiple patient cohorts. This study aimed to identify robust gene classifiers that could be used for the accurate prediction of relapse in independent cohorts and across different experimental platforms.
Using HG-U133Plus2 microarrays we modeled a five-gene classifier (5-GC) that accurately predicted clinical outcome in a cohort of 50 T-ALL patients. The 5-GC was further tested against three independent cohorts of T-ALL patients, using either qRT-PCR or microarray gene expression, and could predict patients with significantly adverse clinical outcome in each. The 5-GC featured the interleukin-7 receptor (IL-7R), low-expression of which was independently predictive of relapse in T-ALL patients. In T-ALL cell lines, low IL-7R expression was correlated with diminished growth response to IL-7 and enhanced glucocorticoid resistance. Analysis of biological pathways identified the NF-κB and Wnt pathways, and the cell adhesion receptor family (particularly integrins) as being predictive of relapse. Outcome modeling using genes from these pathways identified patients with significantly worse relapse-free survival in each T-ALL cohort.
We have used two different approaches to identify, for the first time, robust gene signatures that can successfully discriminate relapse and CCR patients at the time of diagnosis across multiple patient cohorts and platforms. Such genes and pathways represent markers for improved patient risk stratification and potential targets for novel T-ALL therapies.
The cure rates for childhood acute leukemia have dramatically improved to approximately 70% overal, with treatments that include intensive cytotoxic chemotherapy and, in some cases, hematopoietic stem cell transplantation. However, many children still die of their disease or of treatment-related toxicities. Even in patients that are cured, there can be significant and, not uncommonly debilitating, acute and late complications of treatment. Improved understanding of the molecular and cellular biology of leukemia and the increasing availability of high-throughput genomic techniques have facilitated the development of molecularly targeted therapies that have the potential to be more effective and less toxic than the standard approaches. In this article, we review the progress to date with agents that are showing promise in the treatment of childhood acute leukemia, including monoclonal antibodies, inhibitors of kinases and other signaling molecules (e.g., BCR–ABL, FLT3, farnesyltransferase, mTOR and γ-secretase), agents that target epigenetic regulation of gene expression (DNA methyltransferase inhibitors and histone deacetylase inhibitors) and proteasome inhibitors. For the specific agents in each of these classes, we summarize the published preclinical data and the clinical trials that have been completed, are in progress or are being planned for children with acute leukemia. Finally, we discuss potential challenges to the success of molecularly targeted therapy, including proper target identification, adequate targeting of leukemia stem cells, developing synergistic and tolerable combinations of agents and designing adequately powered clinical trials to test efficacy in molecularly defined subsets of patients.
acute lymphoblastic leukemia; acute myeloid leukemia; BCR-ABL; epigenetics; FLT3; immunotherapy; mTOR; notch; proteasome; RAS
To identify children with acute lymphoblastic leukemia (ALL) at initial diagnosis who are at risk for inferior response to therapy by using molecular signatures.
Patients and Methods
Gene expression profiles were generated from bone marrow blasts at initial diagnosis from a cohort of 99 children with National Cancer Institute–defined high-risk ALL who were treated uniformly on the Children's Oncology Group (COG) 1961 study. For prediction of early response, genes that correlated to marrow status on day 7 were identified on a training set and were validated on a test set. An additional signature was correlated with long-term outcome, and the predictive models were validated on three large, independent patient cohorts.
We identified a 24–probe set signature that was highly predictive of day 7 marrow status on the test set (P = .0061). Pathways were identified that may play a role in early blast regression. We have also identified a 47–probe set signature (which represents 41 unique genes) that was predictive of long-term outcome in our data set as well as three large independent data sets of patients with childhood ALL who were treated on different protocols. However, we did not find sufficient evidence for the added significance of these genes and the derived predictive models when other known prognostic features, such as age, WBC, and karyotype, were included in a multivariate analysis.
Genes and pathways that play a role in early blast regression may identify patients who may be at risk for inferior responses to treatment. A fully validated predictive gene expression signature was defined for high-risk ALL that provided insight into the biologic mechanisms of treatment failure.
Treatment of childhood relapsed acute lymphoblastic leukemia (ALL) remains a significant challenge. The goal of the Children's Oncology Group (COG) AALL01P2 study was to develop a safe and active chemotherapy reinduction platform, which could be used to evaluate novel agents in future trials.
Patients and Methods
One hundred twenty-four patients with ALL and first marrow relapse received three, 35-day blocks of reinduction chemotherapy: 69 with early relapse (ER; < 36 months from initial diagnosis) and 55 with late relapse (LR). Minimal residual disease (MRD) was measured by flow cytometry after each treatment block.
Second complete remission (CR2) rates at the end of block 1 in 117 assessable patients were 68% ± 6% for ER (n = 63) and 96% ± 3% for LR (n = 54; P < .0001). Five of seven patients with T-cell ALL (T-ALL) failed to achieve CR2. Among patients in CR2, MRD greater than 0.01% was detected at the end of block 1 in 75% ± 7% of ER (n = 36) versus 51% ± 8% of LR (n = 43; P = .0375) and 12-month event-free survival was 80% ± 7% versus 58% ± 7% in MRD-negative versus positive patients (P < .0005). Blocks 2 and 3 of therapy resulted in reduction of MRD burden in 40 of 56 patients who were MRD positive after block 1. Toxicity was acceptable during all three blocks with five deaths (4%) from infections.
The AALL01P2 regimen is a tolerable and active reinduction platform, suitable for testing in combination with novel agents in B-precursor ALL. Alternative strategies are needed for T-ALL. Serial MRD measurements were feasible and prognostic of outcome.
A full-term neonate suffered multifocal cerebral infarctions due to multiple large vessel thrombi. Thrombophilia and cardiovascular assessments were negative, but due to the severity of the lesions and the concern for expansion of the thrombi or future embolic events, treatment with low-molecular-weight heparin (LMWH) was initiated. No complications from treatment were experienced. We present this severe case in order to highlight difficult management decisions for newborns with multifocal perinatal thromboembolic stroke and to stress the need for further practice guidelines and research in this area.
Acute lymphoblastic leukemia (ALL) is curable in over 80% of children and adolescents with high-risk features. However, current therapies are associated with symptomatic osteonecrosis that disproportionately affects adolescents, often requires surgery, and is one of the most common causes of short- and long-term morbidity. A strategy is needed to lessen this risk.
CCG-1961, a multi-cohort randomized cooperative group trial, evaluated components of therapeutic intensification in 2056 eligible, newly diagnosed high-risk patients (white blood cell count ≥50×109/L and/or age ≥10 years). To address osteonecrosis, a novel alternate-week dexamethasone schedule (10 mg/m2/day on days 0-6 and 14-20) was compared to standard continuous dexamethasone (10 mg/m2/day on days 0-20) in randomized regimens with either double or single delayed intensification phases, respectively. Randomization was done based on a randomization schedule generated using permuted blocks within strata. Patients were prospectively monitored clinically for osteonecrosis, with confirmatory imaging of suspected sites. Primary analyses were performed on an intent-to-treat basis and focused on the estimation and comparison of cumulative incidence rates of osteonecrosis both overall and in patient subgroups (age, gender, marrow early response status); final results are herein reported. This study is registered with ClinicalTrials.gov, number NCT00002812.
Symptomatic osteonecrosis was diagnosed in 143 patients at 377 confirmed skeletal sites, resulting in 139 surgeries. The overall cumulative incidence of osteonecrosis was 7·7% (N=2056) at 5 years, correlating with age at ALL diagnosis (1-9 years 1·0% (N=769), 10-15 years 9·9% (N=1025), ≥16 years 20·0% (N=262), p<0·0001) and gender (≥10 years, female 15·7% (N=525) versus male 9·3% (N=762), p=0·0010). For patients ≥10 years old with a rapid response to induction therapy, the use of alternate-week dexamethasone during delayed intensification phases significantly reduced osteonecrosis incidence compared with continuous dexamethasone (8·7±2·1% (N=420) versus 17·0±2·9% (N=403), p=0·0005), especially those ≥16 years (11·3±5·3% (N=84) versus 37·5±11·1% (N=79), p=0·0003; females 17·2±8·1% (N=32) versus 43·9±14·1% (N=23), p=0·050; males 7·7±5·9% (N=53) versus 34·6±11·6% (N=56), p=0·0014).
Alternate-week dexamethasone during delayed intensification phases effectively reduces osteonecrosis risk in children and adolescents receiving intensified therapy for high-risk ALL.
Recent genome-wide screens have identified genetic variations in ARID5B associated with susceptibility to childhood acute lymphoblastic leukemia (ALL). We sought to determine the contribution of ARID5B single nucleotide polymorphisms (SNPs) to racial disparities in ALL susceptibility and treatment outcome.
Patients and Methods
We compared the association between ARID5B SNP genotype and ALL susceptibility in whites (> 95% European genetic ancestry; 978 cases and 1,046 controls) versus in Hispanics (> 10% Native American ancestry; 330 cases and 541 controls). We determined the relationships between ARID5B SNP genotype and ALL relapse risk in 1,605 children treated on the Children's Oncology Group (COG) P9904/9905 clinical trials.
Among 49 ARID5B SNPs interrogated, 10 were significantly associated with ALL susceptibility in both whites and Hispanics (P < .05), with risk alleles consistently more frequent in Hispanics than in whites. rs10821936 exhibited the most significant association in both races (P = 8.4 × 10−20 in whites; P = 1 × 10−6 in Hispanics), and genotype at this SNP was highly correlated with local Native American genetic ancestry (P = 1.8 × 10−8). Multivariate analyses in Hispanics identified an additional SNP associated with ALL susceptibility independent of rs10821936. Eight ARID5B SNPs were associated with both ALL susceptibility and relapse hazard; the alleles related to higher ALL incidence were always linked to poorer treatment outcome and were more frequent in Hispanics.
ARID5B polymorphisms are important determinants of childhood ALL susceptibility and treatment outcome, and they contribute to racial disparities in this disease.