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1.  A Phase I Study of EZN-3042, a Novel Survivin Messenger Ribonucleic Acid (mRNA) Antagonist, Administered in Combination with Chemotherapy in Children with Relapsed Acute Lymphoblastic Leukemia (ALL): A Report from the Therapeutic Advances in Childhood Leukemia and Lymphoma (TACL) Consortium 
To address therapeutic challenges in childhood relapsed ALL, a phase 1 study combining a survivin mRNA antagonist, EZN-3042, with re-induction chemotherapy was developed for pediatric patients with second or greater bone marrow relapses of B lymphoblastic leukemia. EZN-3042 was administered as a single agent on days -5 and -2 and then in combination with a 4-drug re-induction platform on days 8, 15, 22 and 29. Toxicity and the biological activity of EZN-3042 were assessed. Six patients enrolled at dose level 1 (EZN-3042 2.5 mg/kg/dose). Two dose limiting toxicities were observed: one patient developed a grade 3 GGT elevation and another patient developed grade 3 gastrointestinal bleeding. Downmodulation of survivin mRNA and protein was assessed after single agent dosing and decreased expression was observed in 2 of 5 patients with sufficient material for analysis. While some biological activity was observed, the combination of EZN-3042 with intensive re-induction chemotherapy was not tolerated at a dose that led to consistent downregulation of survivin expression. The trial was terminated following the completion of dose level 1, after further clinical development of this agent was halted.
PMCID: PMC4238428  PMID: 24276047
Relapsed ALL; survivin; antisense
2.  Impact on Survival and Toxicity by Duration of Weight Extremes During Treatment for Pediatric Acute Lymphoblastic Leukemia: A Report From the Children's Oncology Group 
Journal of Clinical Oncology  2014;32(13):1331-1337.
Previous studies regarding the influence of weight on event-free survival (EFS) and treatment-related toxicity (TRT) in childhood acute lymphoblastic leukemia (ALL) considered only weight at diagnosis. Inasmuch as weight varies substantially over treatment, we hypothesized its impact on EFS is instead determined by cumulative time spent at an extreme weight during therapy and on TRT by weight at the time of toxicity.
Patients and Methods
In a cohort of 2,008 children treated for high-risk ALL in Children's Oncology Group study CCG-1961, we determined the effect on EFS of cumulative time receiving therapy at an extreme weight (either obese or underweight) between end of induction and start of maintenance therapy. We also evaluated the association between weight category and incidence and patterns of TRT during 13,946 treatment courses.
Being obese or underweight at diagnosis and for ≥ 50% of the time between end of induction and start of maintenance therapy resulted in inferior EFS (hazard ratios, 1.43 and 2.30, respectively; global P < .001). Normalization of weight during that period resulted in mitigation of this risk comparable to never being obese or underweight. Obese or underweight status at start of each treatment course was significantly associated with specific patterns of TRT.
Influence of weight extremes on EFS and TRT is not set at diagnosis as previously reported but is moderated by subsequent weight status during intensive postinduction treatment phases. These observations suggest that weight is a potentially addressable risk factor to improve EFS and morbidity in pediatric ALL.
PMCID: PMC3992723  PMID: 24687836
3.  CD19-antigen specific nanoscale liposomal formulation of a SYK P-site inhibitor causes apoptotic destruction of human B-precursor leukemia cells 
We report the anti-leukemic potency of a unique biotargeted nanoscale liposomal nanoparticle (LNP) formulation of the spleen tyrosine kinase (SYK) P-site inhibitor C61. C61-loaded LNP were decorated with a murine CD19-specific monoclonal antibody directed against radiation-resistant CD19-receptor positive aggressive B-precursor acute lymphoblastic leukemia (ALL) cells. The biotargeted C61-LNP were more potent than untargeted C61-LNP and consistently caused apoptosis in B-precursor ALL cells. The CD19-directed C61-LNP also destroyed B-precursor ALL xenograft cells and their leukemia-initiating in vivo clonogenic fraction. This unique nanostructural therapeutic modality targeting the SYK-dependent anti-apoptotic blast cell survival machinery shows promise for overcoming the clinical radiochemotherapy resistance of B-precursor ALL cells.
PMCID: PMC4158964  PMID: 24910947
4.  High-Resolution Melting Curve Analysis, a Rapid and Affordable Method for Mutation Analysis in Childhood Acute Myeloid Leukemia 
Background: Molecular genetic alterations with prognostic significance have been described in childhood acute myeloid leukemia (AML). The aim of this study was to establish cost-effective techniques to detect mutations of FMS-like tyrosine kinase 3 (FLT3), nucleophosmin 1 (NPM1), and a partial tandem duplication within the mixed-lineage leukemia (MLL-PTD) genes in childhood AML.
Procedure: Ninety-nine children with newly diagnosed AML were included in this study. We developed a fluorescent dye SYTO-82 based high-resolution melting (HRM) curve analysis to detect FLT3 internal tandem duplication (FLT3-ITD), FLT3 tyrosine kinase domain (FLT3-TKD), and NPM1 mutations. MLL-PTD was screened by real-time quantitative PCR.
Results: The HRM methodology correlated well with gold standard Sanger sequencing with less cost. Among the 99 patients studied, the FLT3-ITD mutation was associated with significantly worse event-free survival (EFS). Patients with the NPM1 mutation had significantly better EFS and overall survival. However, HRM was not sensitive enough for minimal residual disease monitoring.
Conclusion: High-resolution melting was a rapid and efficient method for screening of FLT3 and NPM1 gene mutations. It was both affordable and accurate, especially in resource underprivileged regions. Our results indicated that HRM could be a useful clinical tool for rapid and cost-effective screening of the FLT3 and NPM1 mutations in AML patients.
PMCID: PMC4158872  PMID: 25250304
FLT3; NPM1; MLL; high-resolution melting curve analysis; acute myeloid leukemia; childhood
5.  Constitutive Function of the Ikaros Transcription Factor in Primary Leukemia Cells from Pediatric Newly Diagnosed High-Risk and Relapsed B-precursor ALL Patients 
PLoS ONE  2013;8(11):e80732.
We examined the constitutive function of the Ikaros (IK) transcription factor in blast cells from pediatric B-precursor acute lymphoblastic leukemia (BPL) patients using multiple assay platforms and bioinformatics tools. We found no evidence of diminished IK expression or function for primary cells from high-risk BPL patients including a Philadelphia chromosome (Ph)+ subset. Relapse clones as well as very aggressive in vivo clonogenic leukemic B-cell precursors isolated from spleens of xenografted NOD/SCID mice that developed overt leukemia after inoculation with primary leukemic cells of patients with BPL invariably and abundantly expressed intact IK protein. These results demonstrate that a lost or diminished IK function is not a characteristic feature of leukemic cells in Ph+ or Ph- high-risk BPL.
PMCID: PMC3835424  PMID: 24278314
6.  Alternate-Week versus Continuous Dexamethasone Scheduling on the Risk of Osteonecrosis in Acute Lymphoblastic Leukemia: Results from the CCG-1961 Randomized Cohort Trial 
The lancet oncology  2012;13(9):906-915.
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, 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.
PMCID: PMC3448283  PMID: 22901620
7.  Improved Survival for Children and Adolescents With Acute Lymphoblastic Leukemia Between 1990 and 2005: A Report From the Children's Oncology Group 
Journal of Clinical Oncology  2012;30(14):1663-1669.
To examine population-based improvements in survival and the impact of clinical covariates on outcome among children and adolescents with acute lymphoblastic leukemia (ALL) enrolled onto Children's Oncology Group (COG) clinical trials between 1990 and 2005.
Patients and Methods
In total, 21,626 persons age 0 to 22 years were enrolled onto COG ALL clinical trials from 1990 to 2005, representing 55.8% of ALL cases estimated to occur among US persons younger than age 20 years during this period. This period was divided into three eras (1990-1994, 1995-1999, and 2000-2005) that included similar patient numbers to examine changes in 5- and 10-year survival over time and the relationship of those changes in survival to clinical covariates, with additional analyses of cause of death.
Five-year survival rates increased from 83.7% in 1990-1994 to 90.4% in 2000-2005 (P < .001). Survival improved significantly in all subgroups (except for infants age ≤ 1 year), including males and females; those age 1 to 9 years, 10+ years, or 15+ years; in whites, blacks, and other races; in Hispanics, non-Hispanics, and patients of unknown ethnicity; in those with B-cell or T-cell immunophenotype; and in those with National Cancer Institute (NCI) standard- or high-risk clinical features. Survival rates for infants changed little, but death following relapse/disease progression decreased and death related to toxicity increased.
This study documents ongoing survival improvements for children and adolescents with ALL. Thirty-six percent of deaths occurred among children with NCI standard-risk features emphasizing that efforts to further improve survival must be directed at both high-risk subsets and at those children predicted to have an excellent chance for cure.
PMCID: PMC3383113  PMID: 22412151
8.  Outcomes after Induction Failure in Childhood Acute Lymphoblastic Leukemia 
The New England Journal of Medicine  2012;366(15):1371-1381.
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.)
PMCID: PMC3374496  PMID: 22494120
9.  Toxicity Assessment of Molecularly Targeted Drugs Incorporated into Multiagent Chemotherapy Regimens for Pediatric Acute Lymphocytic Leukemia (ALL): Review from an International Consensus Conference 
Pediatric blood & cancer  2010;54(7):872-878.
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 ( 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.
PMCID: PMC2857540  PMID: 20127846
ALL; ALL relapse; developmental therapeutics; dose-limiting toxicity; maximum tolerated dose
10.  Outcome of Patients Treated for Relapsed or Refractory Acute Lymphoblastic Leukemia: A Therapeutic Advances in Childhood Leukemia Consortium Study 
Journal of Clinical Oncology  2009;28(4):648-654.
Despite improvements in treatment, approximately 20% of patients with acute lymphoblastic leukemia (ALL) experience relapse and do poorly. The Therapeutic Advances in Childhood Leukemia (TACL) Consortium was assembled to assess novel drugs for children with resistant leukemia. We hypothesize that novel agents and combinations that fail to improve baseline complete remission rates in comparable populations are unlikely to contribute to better outcomes and should be abandoned. We sought to define response rates and disease-free survival (DFS) rates in patients treated at TACL institutions, which could serve as a comparator for future studies.
Patients and Methods
We performed a retrospective cohort review of patients with relapsed and refractory ALL previously treated at TACL institutions between the years of 1995 and 2004. Data regarding initial and relapsed disease characteristics, disease response, and survival were collected and compared with those of published reports.
Complete remission (CR) rates (mean ± SE) were 83% ± 4% for early first marrow relapse, 93% ± 3% for late first marrow relapse, 44% ± 5% for second marrow relapse, and 27% ± 6% for third marrow relapse. Five-year DFS rates in CR2 and CR3 were 27% ± 4% and 15% ± 7% respectively.
We generally confirm a 40% CR rate for second and subsequent relapse, but our remission rate for early first relapse seems better than that reported in the literature (83% v approximately 70%). Our data may allow useful modeling of an expected remission rate for any population of patients who experience relapse.
PMCID: PMC2815999  PMID: 19841326
11.  Improved Early Event-Free Survival With Imatinib in Philadelphia Chromosome–Positive Acute Lymphoblastic Leukemia: A Children's Oncology Group Study 
Journal of Clinical Oncology  2009;27(31):5175-5181.
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.
PMCID: PMC2773475  PMID: 19805687
12.  Young Adults With Acute Lymphoblastic Leukemia Have an Excellent Outcome With Chemotherapy Alone and Benefit From Intensive Postinduction Treatment: A Report From the Children's Oncology Group 
Journal of Clinical Oncology  2009;27(31):5189-5194.
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.
PMCID: PMC3053149  PMID: 19805689
13.  Phase II Study of Clofarabine in Pediatric Patients With Refractory or Relapsed Acute Myeloid Leukemia 
Journal of Clinical Oncology  2009;27(26):4392-4397.
To determine the efficacy and safety of clofarabine in pediatric patients with refractory or relapsed acute myeloid leukemia (AML).
Patients and Methods
A phase II, open-label, multicenter study was conducted with single-agent clofarabine in pediatric patients with refractory or relapsed AML. Clofarabine was administered intravenously over 2 hours at the pediatric maximum-tolerated dose (MTD) of 52 mg/m2 daily for 5 consecutive days. Cycles were repeated every 2 to 6 weeks. Responses determined by an independent response review panel.
The 42 patients treated on the study had a median age of 13 years (range, 2 to 22 years) and had received a median number of two (range, one to five) prior regimens. The response rate was 26% and included one complete response without platelet recovery and 10 partial responses. The median duration of response was 20 weeks (range, 2 to ≥ 156 weeks). Six of 28 patients who were refractory to the immediately preceding therapy achieved response. Thirteen patients (31%), including seven responders, proceeded to hematopoietic stem-cell transplantation (HSCT) after treatment with clofarabine and survived between 24 to ≥ 160 weeks. Five patients (12%) remain alive post-transplantation at ≥ 63, ≥ 71, ≥ 86, ≥ 114, and ≥ 130 weeks. The most common grade 3 or greater adverse events without regard to causality were febrile neutropenia, catheter-related infection, epistaxis, hypotension, nausea, and fever. Transient elevation of liver enzymes and hypokalemia occurred frequently. Five patients died within 30 days of clofarabine administration secondary to progressive disease, and another five died as a result of an adverse event.
Clofarabine is active in pediatric patients with multiply relapsed or refractory AML. Responses allowed several refractory patients to proceed to HSCT. The toxicity profile was expected in this patient population.
PMCID: PMC2744276  PMID: 19652076
14.  Long Term Results of the Children’s Cancer Group Studies for Childhood Acute Lymphoblastic Leukemia 1983–2002: a Children’s Oncology Group Report 
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.
PMCID: PMC2906139  PMID: 20016531
Acute lymphoblastic leukemia; children; randomized clinical trials
15.  Factors Influencing Survival After Relapse From Acute Lymphoblastic Leukemia: A Children's Oncology Group Study 
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.
PMCID: PMC2872117  PMID: 18818707
relapsed acute lymphoblastic leukemia; Children's Oncology Group; pediatric
16.  Reinduction Platform for Children With First Marrow Relapse of Acute Lymphoblastic Leukemia: A Children's Oncology Group Study 
Journal of Clinical Oncology  2008;26(24):3971-3978.
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.
PMCID: PMC2654313  PMID: 18711187
17.  Treating refractory leukemias in childhood, role of clofarabine 
Approximately 4000 children and adolescents under the age of 20 years develop acute leukemia per year in the US. Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. Despite impressive improvements in outcome, relapsed ALL is the fourth most common pediatric malignancy. Therapy for relapsed ALL remains unsatisfactory, and the majority of relapse patients still succumb to leukemia. Between one-third and one-half of patients with acute myelogenous leukemia (AML) relapse, and no standard therapy is recognized for patients with relapsed and/or refractory AML. Novel therapeutic agents are needed to improve the cure rate for relapsed ALL and AML. Clofarabine is a next-generation nucleoside analog, designed to incorporate the best features and improve the therapeutic index of cladribine and fludarabine. Clofarabine inhibits both DNA polymerase and ribonucleotide reductase, leading to impaired DNA synthesis and repair, and directly induces apoptosis. Phase I and II single-agent trials in children have shown that clofarabine is safe and active in both myeloid and lymphoid relapsed/refractory acute leukemias. Clofarabine has been approved by the FDA for pediatric patients with relapsed/refractory ALL after at least 2 prior therapeutic attempts. Rational combinations of clofarabine with other active agents in refractory leukemias are currently under investigation.
PMCID: PMC2504075  PMID: 18728851
clofarabine; leukemia; refractory; pediatric; childhood

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