Induction failure in acute lymphoblastic leukemia of childhood

CBAP regulates the function of Akt-associated TSC protein complexes to modulate mTORC1 signaling

The Akt-Rheb-mTORC1 pathway plays a crucial role in regulating cell growth, but the mechanisms underlying the activation of Rheb-mTORC1 by Akt remain unclear. In our previous study, we found that CBAP was highly expressed in human T-ALL cells and primary tumors, and its deficiency led to reduced phosphorylation of TSC2/S6K1 signaling proteins as well as impaired cell proliferation and leukemogenicity. We also demonstrated that CBAP was required for Akt-mediated TSC2 phosphorylation in vitro. In response to insulin, CBAP was also necessary for the phosphorylation of TSC2/S6K1 and the dissociation of TSC2 from the lysosomal membrane. Here we report that CBAP interacts with AKT and TSC2, and knockout of CBAP or serum starvation leads to an increase in TSC1 in the Akt/TSC2 immunoprecipitation complexes. Lysosomal-anchored CBAP was found to override serum starvation and promote S6K1 and 4EBP1 phosphorylation and c-Myc expression in a TSC2-dependent manner. Additionally, recombinant CBAP inhibited the GAP activity of TSC2 complexes in vitro, leading to increased Rheb-GTP loading, likely due to the competition between TSC1 and CBAP for binding to the HBD domain of TSC2. Overexpression of the N26 region of CBAP, which is crucial for binding to TSC2, resulted in a decrease in mTORC1 signaling and an increase in TSC1 association with the TSC2/AKT complex, ultimately leading to increased GAP activity toward Rheb and impaired cell proliferation. Thus, we propose that CBAP can modulate the stability of TSC1-TSC2 as well as promote the translocation of TSC1/TSC2 complexes away from lysosomes to regulate Rheb-mTORC1 signaling.

Outcome for Children and Young Adults With T-Cell ALL and Induction Failure in Contemporary Trials

PURPOSE

Historically, patients with T-cell acute lymphoblastic leukemia (T-ALL) who fail to achieve remission at the end of induction (EOI) have had poor long-term survival. The goal of this study was to examine the efficacy of contemporary therapy, including allogeneic hematopoietic stem cell transplantation (HSCT) in first remission (CR1).

METHODS

Induction failure (IF) was defined as the persistence of at least 5% bone marrow (BM) lymphoblasts and/or extramedullary disease after 4-6 weeks of induction chemotherapy. Disease features and clinical outcomes were reported in 325 of 6,167 (5%) patients age 21 years and younger treated in 14 cooperative study groups between 2000 and 2018.

RESULTS

With a median follow-up period of 6.4 years (range, 0.3-17.9 years), the 10-year overall survival (OS) was 54.7% (SE = 2.9), which is significantly higher than the 27.6% (SE = 2.9) observed in the historical cohort from 1985 to 2000. There was no significant impact of sex, age, white blood cell count, central nervous system disease status, T-cell maturity, or BM disease burden at EOI on OS. Postinduction complete remission (CR) was achieved in 93% of patients with 10-year OS of 59.6% (SE = 3.1%) and disease-free survival (DFS) of 56.3% (SE = 3.1%). Among the patients who achieved CR, 72% underwent HSCT and their 10-year DFS (with a 190-day landmark) was significantly better than nontransplanted patients (63.8% [SE = 3.6] v 45.5% [SE = 7.1]; P = .005), with OS of 66.2% (SE = 3.6) versus 50.8% (SE = 6.8); P = .10, respectively.

CONCLUSION

Outcomes for patients age 21 years and younger with T-ALL and IF have improved in the contemporary treatment era with a DFS benefit among those undergoing HSCT in CR1. However, outcomes still lag considerably behind those who achieve remission at EOI, warranting investigation of new treatment approaches.

Outcomes following induction failure in Japanese children with acute lymphoblastic leukemia

The characteristics and prognosis of Japanese children with acute lymphoblastic leukemia (ALL) who fail to achieve complete remission after remission induction chemotherapy (i.e., experience induction failure) are poorly understood. Therefore, we retrospectively analyzed data of patients enrolled in Japanese clinical trials for newly diagnosed ALL between 1996 and 2009. Among 4956 participants, 89 (1.8%) experienced induction failure. With a 6.0-year median follow-up, the 5-year overall survival rate of the entire cohort was 43.0% ± 5.5%. Survival rates did not differ between patients with B-cell precursor ALL (BCP-ALL) and T-cell ALL (T-ALL). In multivariate analysis, day 15 M3 marrow (bone marrow blast count ≥ 25%) was significantly correlated with poorer survival in the whole or BCP-ALL cohorts. In T-ALL, age < 6 years was significantly associated with poor survival. However, due to the small sample size, this correlation must be further investigated. Most T-ALL and BCR-ABL-positive BCP-ALL patients underwent allogeneic stem cell transplantation (allo-SCT). Survival rates did not differ between BCR-ABL-negative BCP-ALL patients who did and did not undergo allo-SCT, possibly due to the inclusion of lower-risk patients in the latter group. In conclusion, the induction failure rate and survival after diagnosis of induction failure in our study were comparable to previously reported figures.

Réponse à un schéma chimiothérapeutique administré à des enfants atteints de LAL à cellules pré-B à risque élevé selon le protocole COG

Objectif

La présente étude a pour but d'examiner la réponse à un schéma chimiothérapeutique administré à des enfants atteints de LAL à cellules pré-B à risque élevé selon le protocole COG.

Méthode

L'étude transversale porte sur 55 enfants traités selon le protocole du groupe d'oncologie pédiatrique (mieux connu sous le nom de Children's Oncology Group ou COG), de septembre 2010 à février 2015, et évalue les résultats du schéma chimiothérapeutique.

Résultats

Durant la première semaine suivant le traitement, le taux de rétablissement complet a été de 76,4 %. Les taux de survie après trois ans et cinq ans étaient respectivement de 85,5 % et de 81 %. Le taux de rechute après le premier épisode de rémission a été de 20 % et le taux de mortalité consécutif à cette rechute a été de 50 %. Trente pour cent de l'ensemble des décès ont eu lieu durant la période d'induction. Dans tous les cas, une septicémie en est la cause.

Conclusion

Les résultats indiquent que le taux de survie a augmenté. Il est donc possible d'améliorer le taux de survie en optant pour le protocole COG et en contrôlant les infections chez les patients, et ce, sans égard au groupe de risque.

The outcome of chemotherapeutic regimen by high-risk pre-B-cell protocol in ALL children

Objective

The aim of this study was to investigate the outcome of chemotherapeutic regimen by high-risk pre-B-cell potocol in ALL children.

Methods

The cross-sectional study was conducted on 55 children who were treated with the Children Oncology Group (COG) protocol from September 2010 to February 2015 to evaluate the chemotherapeutic regimen results.

Results

There was a complete recovery rate of 76.4% during the first week after treatment. Three-year overall survival was 85.5% and five-year overall survival was 81%. Relapse rate after first remission was 20% and death after relapse was 50%. Thirty percent of total deaths were at the induction period. All of the deceased cases died due to sepsis.

Conclusion

Results showed that the survival rate increased. By choosing the COG protocol and by controlling infection in patients without considering the risk group we can improve survival rates.

Replacing cyclophosphamide/cytarabine/mercaptopurine with cyclophosphamide/etoposide during consolidation/delayed intensification does not improve outcome for pediatric B-cell acute lymphoblastic leukemia: a report from the COG

With modern chemotherapy, approximately 90% of patients with pediatric acute lymphoblastic leukemia are now cured. However, subsets of patients can be identified who remain at very high risk of relapse with expected 4-year disease-free survival rates <80%; such patients are appropriate candidates for intensive therapeutic strategies designed to improve survival. The AALL1131 trial was designed to determine, in a randomized fashion, whether substitution with cyclophosphamide/etoposide (experimental arm 1) would improve the 4-year disease-free survival of children, adolescents, and young adults with very high-risk B-cell acute lymphoblastic leukemia compared to a modified Berlin-Frankfurt-Münster regimen (control arm). Patients 1-30 years of age with newly diagnosed very high-risk B-cell acute lymphoblastic leukemia were randomized after induction in a 1:2 fashion to the control arm or experimental arm 1 in which they were given cyclophosphamide (440 mg/m² days 1-5)/etoposide (100 mg/m² days 1-5) during part 2 of consolidation and delayed intensification. Prospective interim monitoring rules for efficacy and futility were included where futility would be determined for a one-sided P-value ≥0.7664. The study was stopped for futility as the interim monitoring boundary was crossed [hazard ratio 0.606 (95% confidence interval: 0.297 - 1.237)] and the very high-risk arm of AALL1131 was closed in February 2017. Using data current as of December 31, 2017, 4-year disease-free survival rates were 85.5±6.8% (control arm) versus 72.3±6.3% (experimental arm 1) (P-value = 0.76). There were no significant differences in grade 3/4 adverse events between the two arms. Substitution of this therapy for very high-risk B-cell acute lymphoblastic leukemia patients on the Children’s Oncology Group AALL1131 trial (NCT02883049) randomized to cyclophosphamide/etoposide during part 2 of consolidation and delayed intensification did not improve disease-free survival.

CBAP modulates Akt-dependent TSC2 phosphorylation to promote Rheb-mTORC1 signaling and growth of T-cell acute lymphoblastic leukemia

High-frequency relapse remains a clinical hurdle for complete remission of T-cell acute lymphoblastic leukemia (T-ALL) patients, with heterogeneous dysregulated signaling profiles—including of Raf-MEK-ERK and Akt-mTORC1-S6K signaling pathways—recently being implicated in disease outcomes. Here we report that GM-CSF/IL-3/IL-5 receptor common β-chain-associated protein (CBAP) is highly expressed in human T-ALL cell lines and many primary tumor tissues and is required to bolster leukemia cell proliferation in tissue culture and for in vivo leukemogenesis in a xenograft mouse model. Downregulation of CBAP markedly restrains expansion of leukemia cells and alleviates disease aggravation of leukemic mice. Transcriptomic profiling and molecular biological analyses suggest that CBAP acts upstream of Ras and Rac1, and functions as a modulator of both Raf-MEK–ERK and Akt-mTORC1 signaling pathways to control leukemia cell growth. Specifically, CBAP facilitated Akt-dependent TSC2 phosphorylation in cell-based assays and in vitro analysis, decreased lysosomal localization of TSC2, and elevated Rheb-GTP loading and subsequent activation of mTORC1 signaling. Taken together, our findings reveal a novel oncogenic contribution of CBAP in T-ALL leukemic cells, in addition to its original pro-apoptotic function in cytokine-dependent cell lines and primary hematopoietic cells, by demonstrating its functional role in the regulation of Akt-TSC2-mTORC1 signaling for leukemia cell proliferation. Thus, CBAP represents a novel therapeutic target for many types of cancers and metabolic diseases linked to PI3K-Akt-mTORC1 signaling.

Factors Determining the Outcome of Hematopoietic Stem Cell Transplantation in Patients With Acute Lymphoblastic Leukemia at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia

Medical records of 82 patients with acute lymphoblastic leukemia (ALL) who underwent hematopoietic cell transplantation (HCT) at our institution from 2005 to 2011 were reviewed. Forty-five patients were male (54.8%). The median age at HCT was 7.46 years (range, 0.98 to 14.31 y), the median time to HCT after diagnosis was 12.56 months. Ten patients were below the age of 1 year (12%). All patients were in complete remission at the time of HCT. In 83 transplants, 64 patients received HCT from human leukocyte antigen-identical-related donors and 19 from other donors. Stem cell source was bone marrow in 65 (78%) and cord blood in 18 (22%). Five-year overall survival was 58.8% and event-free survival was 54.3%. The cumulative incidence of acute graft versus host disease was 4.8%±2.3% and of chronic graft versus host disease was 8.9%±3.2%. The median time to absolute neutrophil count and platelet recovery was 17 days (range, 12 to 43 d) and 28 days (range, 15 to 98 d), respectively. One patient acquired CMV infection after transplant. No one developed venoocclusive disease, hemorrhagic cystitis, or other complication. Patient's age at diagnosis, sex, donor's human leukocyte antigen status and sex, source of transplant and complete remission status at HCT did not affect overall survival and event-free survival. Our results show a favorable outcome to HCT for acute lymphoblastic leukemia patients comparable to published data, and no single factor was associated with superior outcome.

Risk factors for relapse in childhood acute lymphoblastic leukemia: prediction and prevention

With current treatment regimens, survival rates for acute lymphoblastic leukemia (ALL) have improved dramatically since the 1980s, with current 5-year overall survival rates estimated at greater than 85%. This success was achieved, in part, through the implementation of risk-stratified therapy. Nevertheless, for a subgroup of patients (15-20%) with newly diagnosed ALL who will ultimately relapse, traditional risk assessment remains inadequate. The risk of relapse may be estimated on the basis of diagnostic features or early treatment response findings. Further progress in this field may thus come from refinement of predictive factors for relapse and treatment adaptation and from the identification of biological subsets of ALL patients who could benefit from specific target therapies. This article summarizes the aspects associated with the identification of predictive factors for relapse in childhood ALL and options available for prevention of disease recurrence.

Long-term outcome of a pediatric-inspired regimen used for adults aged 18-50 years with newly diagnosed acute lymphoblastic leukemia

On the basis of the data suggesting that adolescents and young adult patients with acute lymphoblastic leukemia (ALL) have improved outcomes when treated on pediatric protocols, we assessed the feasibility of treating adult patients aged 18–50 years with ALL with the DFCI Pediatric ALL Consortium regimen utilizing a 30-week course of pharmacokinetically dose-adjusted E. coli L-asparaginase during consolidation. Between 2002 and 2008, 92 eligible patients aged 18–50 years were enrolled at 13 participating centers. Seventy-eight patients (85%) achieved a complete remission (CR) after 1 month of intensive induction therapy. With a median follow-up of 4.5 years, the 4-year disease-free survival (DFS) for the patients achieving a CR was 69% (95% confidence interval (CI) 56–78%) and the 4-year overall survival (OS) for all eligible patients was 67% (95% CI 56–76%). The 4-year DFS for the 64 patients who achieved a CR and were Philadelphia chromosome negative (Ph−) was 71% (95% CI 58–81%), and for all 74 Ph− patients the 4-year OS was 70% (95% CI 58–79%). We conclude that a pediatric-like treatment strategy for young adults with de novo ALL is feasible, associated with tolerable toxicity, and results in improved outcomes compared with historical regimens in young adult patients with ALL.

Postinduction dexamethasone and individualized dosing of Escherichia Coli L-asparaginase each improve outcome of children and adolescents with newly diagnosed acute lymphoblastic leukemia: results from a randomized study--Dana-Farber Cancer Institute ALL Consortium Protocol 00-01

PURPOSE

We assessed the toxicity and efficacy of dexamethasone and a novel dosing method of Escherichia coli L-asparaginase (EC-Asnase) in children and adolescents with newly diagnosed acute lymphoblastic leukemia (ALL).

PATIENTS AND METHODS

Patients achieving complete remission (CR) on Dana-Farber Cancer Institute ALL Consortium Protocol 00-01 were eligible for random assignment to 1) dexamethasone or prednisone, administered as 5-day pulses, every 3 weeks, and 2) weekly EC-Asnase, administered as a 25,000 IU/m(2) fixed dose (FD) or individualized dose (ID) starting at 12,500-IU/m(2), adjusted every 3 weeks based on nadir serum asparaginase activity (NSAA) determinations.

RESULTS

Between 2000 and 2004, 492 evaluable patients (ages 1 to 18 years) enrolled; 473 patients (96%) achieved CR. Four hundred eight patients (86%) participated in the corticosteroid randomization and 384 patients (81%) in the EC-Asnase randomization. With 4.9 years of median follow-up, dexamethasone was associated with superior 5-year event-free survival (EFS; 90% v 81% for prednisone; P = .01) but higher rates of infection (P = .03) and, in older children, higher cumulative incidence of osteonecrosis (P = .02) and fracture (P = .06). ID EC-Asnase had superior 5-year EFS (90% v 82% for FD; P = .04), but did not reduce the frequency of asparaginase-related toxicity. Multivariable analysis identified both dexamethasone and ID EC-Asnase as independent predictors of favorable EFS.

CONCLUSION

There was no overall difference in skeletal toxicity by corticosteroid type; dexamethasone was associated with more infections and, in older children, increased incidence of osteonecrosis and fracture. There was no difference in asparaginase-related toxicity by EC-Asnase dosing method. Dexamethasone and ID EC-Asnase were each associated with superior EFS. Monitoring NSAA during treatment with EC-Asnase may be an effective strategy to improve outcome in pediatric ALL.

Outcomes after induction failure in childhood acute lymphoblastic leukemia

BACKGROUND

Failure of remission-induction therapy is a rare but highly adverse event in children and adolescents with acute lymphoblastic leukemia (ALL).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.).

Pattern of Acute Lymphoblastic Leukemia Among Kurdish Children in Duhok City, Northern Iraq

Although it is a common malignancy, there is a lack of information about leukemias in Kurdish people. To evaluate the pattern of acute lymphoblastic leukemia among Kurdish children in Duhok city/ North of Iraq, and to compare it with available data from other countries, 83 cases were studied of acute lymphoblastic leukemia diagnosed by bone marrow aspiration cytology, cytochemistry and immune-phenotyping between July 2006 and August 2010.

Data recorded included age, sex, area of residence whether rural or urban, socio-economic status, the presenting features and the initial peripheral blood and bone marrow findings. Ages ranged from 7 months to 14.5 years, the peak occurrence was between one and five years and the male to female ratio was 1.7:1. Most patients were low socio-economic class (86.7%), and 68% were living in rural areas.

The most frequent presenting features were pallor (88%) and bleeding tendency (65%), and 25.2% of patients had a leukocyte count above 50,000 per cubic millimetre. L1 and L2 morphology was approximately equal (51.6% and 46.9%, respectively). The percentage of T-cell ALL was higher than the range reported in other countries. Conclusion: Acute lymphoblastic leukemia is an important health problem in Kurdistan region and its pattern differs in certain respects from that reported from different regions of the world though comparable in other aspects. The study recommends implementation of preventive, diagnostic and therapeutic strategies for leukemias in the Kurdistan region.

Outcome of hematopoietic stem cell transplantation of children with very high risk acute lymphoblastic leukemia in first complete remission

Approximately 10% of children with ALL present at diagnosis with VHR for relapse if treated with chemotherapy alone. They may benefit from allogeneic HSCT in CR1. We have reviewed the outcome of this population in our institution. Forty-three patients (median age: 8.9 yr) with VHR ALL in CR1 underwent HSCT from October 1994 to April 2006. VHR features included Philadelphia chromosome (n = 17), induction failure (n = 9), hypodiploidy (n = 6), MLL gene rearrangement (n = 5), and others (n = 6). All patients received TBI (1200 cGy) with either CY and/or etoposide. Stem cell source was unrelated (n = 24) and related (n = 19). Incidence of grade III-IV acute GVHD and chronic extensive GVHD were 25% and 16%, respectively. Twelve patients relapsed (eight received related HSCT). Eleven patients died due to transplant-related mortality (eight received unrelated HSCT). For a median follow up of 39 months (range 11-110), the event free survival and OS were 0.49 (95% CI: 0.31-0.67) and 0.53 (CI: 0.44-0.71), respectively. Outcomes of children with VHR ALL receiving HSCT in CR1 remain unsatisfactory. Relapse, mainly after related HSCT, and TRM, mainly after unrelated HSCT, continue to be major problems.

Erwinia asparaginase after allergy to E. coli asparaginase in children with acute lymphoblastic leukemia

BACKGROUND

Escherichia coli asparaginase is an important component of treatment for childhood acute lymphoblastic leukemia (ALL); however, hypersensitivity develops in up to 30% of patients. We assessed the nadir enzyme activity and tolerability of Erwinia asparaginase, an alternative preparation, in E. coli asparaginase-allergic patients.

PATIENTS AND METHODS

Between 2000 and 2002, 215 children with newly diagnosed ALL were enrolled on Dana-Farber Cancer Institute ALL Consortium Protocol 00-01 and were to receive 30 weekly doses of intramuscular E. coli asparaginase. If E. coli asparaginase allergy developed, patients were switched to twice-weekly intramuscular Erwinia asparaginase (25,000 IU/m(2)). Nadir serum asparaginase activity (NSAA) was measured every 3 weeks.

RESULTS

Forty-two patients (20%) developed E. coli asparaginase allergy and switched to Erwinia. Of 38 patients with evaluable samples, 34 (89%) Erwinia-treated patients had at least one therapeutic NSAA (> or =0.1 IU/ml). The median NSAA was 0.247 IU/ml 3 days and 0.077 IU/ml 4 days after an Erwinia dose. Associated toxicities included allergy in 14 (33%) and pancreatitis in 3 patients (7%). At a median follow-up of 5.4 years, event-free survival (+/-standard error) of the 42 patients who switched to Erwinia was 86 +/- 5% compared with 81 +/- 3% for the 170 patients without E. coli asparaginase allergy (P = 0.55).

CONCLUSIONS

Twice-weekly Erwinia asparaginase was well tolerated and achieved a therapeutically effective NSAA in most E. coli asparaginase-allergic patients. Development of E. coli allergy and subsequent treatment with twice-weekly Erwinia did not adversely impact event-free survival. Erwinia asparaginase should be considered for E. coli asparaginase-allergic patients.

Outcome of childhood acute lymphoblastic leukemia with induction failure treated by the Japan Association of Childhood Leukemia study (JACLS) ALL F-protocol

BACKGROUND

Children with acute lymphoblastic leukemia (ALL) who fail to achieve complete remission (CR) after induction therapy (induction failure: IF) have a poor prognosis; however, there have been few prospective studies in patients with IF.

PATIENTS AND METHODS

Between April 1997 and March 2005, 27 of 1,237 leukemic patients (2.2%) failed to achieve CR after four- or five-drug induction therapy. Twenty-three of these patients entered the F-protocol study, which mainly consisted of acute-myeloid-leukemia-oriented chemotherapy followed by scheduled hematopoietic cell transplantation (HCT).

RESULTS

Seventeen (73.9%) of the 23 patients responded to re-induction chemotherapy with CR. Of note, 15 (93.8%) of 16 patients with Philadelphia-chromosome-negative (non-Ph(+)) ALL achieved CR; in contrast, only 2 (28.6%) of 7 Ph(+) patients achieved CR. Fourteen (82.4%) of 17 patients remained in CR (CCR) until their scheduled HCT, 12 of the 14 with CCR underwent HCT as scheduled, and 6 patients remain in first CR after a median of 78 months (range, 49-107 months). The 5-year overall survival (OS) rates of 16 patients with non-Ph(+) and 7 patients with Ph(+) were 43.8 +/- 12.4% and 14.3 +/- 13.2%, respectively (P = 0.012). The 5-year OS rate of the 17 patients who obtained CR by re-induction therapy and the 6 who did not were 47.1 +/- 12.1% and 0%, respectively (P < 0.001).

CONCLUSION

Acute-myeloid-leukemia-oriented chemotherapy followed by scheduled HCT is a promising treatment strategy for non-Ph(+) ALL patients with IF.

Childhood acute lymphoblastic leukemia: update on prognostic factors

PURPOSE OF REVIEW

With current treatment regimens, event-free survival rates for childhood acute lymphoblastic leukemia (ALL) approach or exceed 80%. This success was achieved, in part, through the implementation of risk-stratified therapy. However, for the 15-20% of children with newly diagnosed ALL who will ultimately relapse, traditional risk assessment remains inadequate. This review highlights recent advances in our understanding of prognostic factors that may be used to refine risk group classification.

RECENT FINDINGS

An increasingly sophisticated understanding of genetic abnormalities in leukemia cells (including chromosomal abnormalities and patterns of gene expression), response to treatment, and host pharmacogenomics offers the potential to enhance or supplant currently applied prognostic criteria for use in treatment planning for childhood ALL.

SUMMARY

Identification of biologically distinctive subsets of ALL through cytogenetic, molecular, and gene expression studies, as well as investigations of minimal residual disease and host pharmacogenomics, offer promising avenues of research. Integration of molecular tools into clinical practice will ultimately allow for more precise risk stratification and individualized treatment planning.

Risk-adapted stratification and treatment of childhood acute lymphoblastic leukaemia

Systematic enrollment of children and adolescents with acute lymphoblastic leukaemia (ALL) into clinical trials has allowed the establishment of prognostic parameters derived from initial diagnostic findings. More important, these trials have significantly contributed to the reduction of disease recurrence as much as to the reduction of acute and late side effects. Some problems that are related to the specificity of the parameters used for risk assessment were not overcome: high tumour load by white blood cell count (WBC), age and (rare) cytogenetic subtypes (e.g. t9;22) may characterise a significant proportion of children and adolescents with high-risk ALL. Most patients who will eventually relapse do not present with characteristic features at initial diagnosis. It appears feasible through careful response assessment to identify these patients at risk of relapse, who present initially without specific features. Earlier trials of the ALL-BFM (Berlin/Frankfurt/Münster) study group and others have demonstrated that inadequate leukaemic blast reduction in the peripheral blood or bone marrow after the first few days of therapy is highly predictive of treatment failure. Using clone-specific polymerase chain reaction-based detection of minimal residual disease (MRD) as done in trial AIEOP-BFM ALL 2000 allowed a close surveillance of specific treatment elements when applied in MRD positive patients. This may facilitate innovative chemotherapy approaches and a more rational use of allogeneic haematopoetic stem cell transplantation. In addition, genetic signatures of treatment response or failure have been identified.

Prognostic factors for leukemic induction failure in children with acute lymphoblastic leukemia and outcome after salvage therapy: the FRALLE 93 study

PURPOSE

To identify prognostic factors and to evaluate the outcome of children with acute lymphoblastic leukemia (ALL) failure after induction therapy.

PATIENTS AND METHODS

Between June 1993 and December 1999, 1,395 leukemic children were included in the French Acute Lymphoblastic Leukemia 93 study.

RESULTS

Fifty-three patients (3.8%) had a leukemic induction failure (LIF) after three- or four-drug induction therapy. In univariate analysis, high WBC count (P = .001), mediastinal mass (P = .017), T-cell phenotype (T-ALL; P = .001), t(9;22) translocation (P = .001), and a slow early response (at day 8 and/or on day 21, P = .001) were predictive of LIF. The following three prognostic groups for LIF were identified by multivariate analysis: a low-risk group with B-cell progenitor (BCP) ALL without t(9;22) (odds ratio [OR] = 1), an intermediate-risk group with T-ALL and a mediastinal mass (OR = 7.4, P < .0001), and a high-risk group with BCP-ALL and t(9;22) or T-ALL without a mediastinal mass (OR = 28.4, P < .0001). Complete remission (CR) was subsequently obtained in 43 patients (81%). The 5-year overall survival (OS) rate of the 53 patients was 30% +/- 6%. The 5-year OS rate among allogeneic graft recipients, autologous graft recipients, and after chemotherapy were 30.4% +/- 9.6% (50% +/- 26% after genoidentical transplantation), 50% +/- 17.7%, and 41.7% +/- 14.2%, respectively (P = .18). Fourteen patients (26%) were still in first CR after a median of 83 months (range, 53 to 117 months).

CONCLUSION

Three risk categories for LIF in children with ALL were identified. Approximately one third of patients with LIF can be successfully treated with salvage therapy overall. Subsequent CR after LIF is mandatory for cure.

Allogeneic bone marrow transplantation in first remission for children with ultra-high-risk features of acute lymphoblastic leukemia: A children's oncology group study report

The prognosis for childhood acute lymphoblastic leukemia (ALL) has improved dramatically over the past quarter of a century. Despite improvements in the treatment of childhood ALL, relapse still occurs in 20%-30% of patients. Although many of these relapses occur in the "standard-risk" patients, approximately 10% of these patients present at diagnosis with clinical and biological features that identify them as having a very high risk of relapse. Children (2 months to 21 years) with > or =1 ultra-high-risk feature (UHRF) of ALL in first remission treated on a frontline Children's Cancer Group (CCG) ALL study with a matched family allogeneic donor were eligible for study entry onto CCG-1921 and an allogeneic bone marrow transplant (AlloBMT). Each patient received fractionated total body irradiation (1200 cGy) and cyclophosphamide (120 mg/kg) conditioning therapy followed by unmobilized BM from a matched family donor. Graft-versus-host disease (GVHD) prophylaxis consisted of methotrexate and cyclosporin. Twenty-nine patients with a median age of 8.7 years with UHRF ALL in first complete remission (CR1) received an AlloBMT from a family member. The incidence of grade II-IV acute GVHD was 20.7% and the incidence of chronic GVHD was 3.7%. AlloBMT conditioning regimen was well tolerated and only 1 patient (3%) had treatment-related mortality. Ten patients (35%) died due to progressive disease. The 5-year event-free survival (EFS) for all patients was 58.6% and patients without cytogenetic abnormalities had a 5-year EFS of 77.8%. The 5-year EFS rates for infants and non-infants were 20.0% and 66.7% (log-rank test, P = .01), respectively. Patients with Philadelphia chromosome-positive ALL had a 5-year EFS of 66.7%. The children with UHRF of ALL may benefit from AlloBMT in CR1, especially patients with primary induction failure and Philadelphia chromosome-positive ALL. Randomized prospective cooperative group studies are required to establish the role of allogeneic hematopoietic stem cell transplantation versus intensive chemotherapy in children with UHRF ALL in CR1.

Pooled analysis of phase II window studies in children with contemporary high-risk metastatic rhabdomyosarcoma: a report from the Soft Tissue Sarcoma Committee of the Children's Oncology Group

PURPOSE

The Soft Tissue Sarcoma Committee of the Children's Oncology Group has conducted five upfront window trials in patients with newly diagnosed metastatic rhabdomyosarcoma to identify promising new treatment agents.

PATIENTS AND METHODS

This pooled analysis identified a total of 420 patients (115 from Intergroup Rhabdomyosarcoma Study III [IRS-III] and 305 from the five window trials). We assessed window therapy response rate, failure-free survival (FFS), and overall survival (OS).

RESULTS

Response rates (complete + partial response) assessed at week 6 of window therapy ranged from 41% to 55% and did not predict FFS (P = .073) or OS (P = .31). FFS was influenced by trial (P = .048); patients enrolled onto IRS-III and the ifosfamide/etoposide and ifosfamide/doxorubicin trials fared best. When grouped and compared with topoisomerase I poison trials, ifosfamide/topoisomerase II inhibitor trials had superior FFS (P = .013). However, there was no difference in survival.

CONCLUSION

Upfront phase II window trials can efficiently provide robust estimates of activity for new agents and combinations in newly diagnosed patients with high-risk rhabdomyosarcoma. Our data indicate that, for some phase II window trials, the risk of treatment failure may be increased but that the trend towards lower survival for some of the window trials compared with IRS-III is not statistically significant. Window nonresponders did not suffer worse FFS or OS than patients who responded to window therapy. Finally, these results provide a rationale for incorporating ifosfamide, etoposide, doxorubicin, and topoisomerase I poisons in future trials of high-risk metastatic rhabdomyosarcoma.

Myths and Lessons from the Adult/Pediatric Interface in Acute Lymphoblastic Leukemia

The development of effective therapy for children with acute lymphoblastic leukemia (ALL) is one of the great successes of clinical oncology, with long-term survival achieved in over 80% of patients. However, cure rates for adults with ALL remain relatively low, with only 40% of patients cured. With an age-unrestricted, biology-based approach, we anticipate a better understanding about why these outcome differences exist, and think that by extending successful pediatric clinical programs to include adult patients with ALL, we can directly compare uniformly treated adults and children in terms of response to therapy, toxicity and underlying biology.

Childhood T-cell acute lymphoblastic leukemia: the Dana-Farber Cancer Institute acute lymphoblastic leukemia consortium experience

PURPOSE

T-cell acute lymphoblastic leukemia (T-ALL) accounts for 10% to 15% of newly diagnosed cases of childhood acute lymphoblastic leukemia (ALL). Historically, T-ALL patients have had a worse prognosis than other ALL patients.

PATIENTS AND METHODS

We reviewed the outcomes of 125 patients with T-ALL treated on Dana-Farber Cancer Institute (DFCI) ALL Consortium trials between 1981 and 1995. Therapy included four- or five-agent remission induction; consolidation therapy with doxorubicin, vincristine, corticosteroid, mercaptopurine, and weekly high-dose asparaginase; and cranial radiation. T-ALL patients were treated the same as high-risk B-progenitor ALL patients. Fifteen patients with T-cell lymphoblastic lymphoma were also treated with the same high-risk regimen between 1981 and 2000.

RESULTS

The 5-year event-free survival (EFS) rate for T-ALL patients was 75% +/- 4%. Fourteen of 15 patients with T-cell lymphoblastic lymphoma were long-term survivors. There was no significant difference in EFS comparing patients with T-ALL and B-progenitor ALL (P =.56), although T-ALL patients had significantly higher rates of induction failure (P <.0001), and central nervous system (CNS) relapse (P =.02). The median time to relapse in T-ALL patients was 1.2 years versus 2.5 years in B-progenitor ALL patients (P =.001). There were no pretreatment characteristics associated with worse prognosis in patients with T-ALL.

CONCLUSION

T-ALL patients fared as well as B-progenitor patients on DFCI ALL Consortium protocols. Patients with T-ALL remain at increased risk for induction failure, early relapse, and isolated CNS relapse. Future studies should focus on the identification of and treatment for T-ALL patients at high risk for treatment failure.

PCR detection of clonal IgH and TCR gene rearrangements at the end of induction as a non-remission criterion in children with ALL: comparison with standard morphologic analysis and risk group classification

BACKGROUND

The initial response to induction therapy is currently considered one of the most important prognostic factors in acute lymphoblastic leukemias (ALL). A series of methods for the detection of submicroscopic levels of residual disease in patients with ALL mainly based on PCR and immunophenotyping has been developed, demonstrating that the presence of high levels of residual disease at the end of induction therapy is an important, independent prognostic factor. We determined the usefulness of PCR detection of minimal residual disease using consensus primers as a non-remission criterion.

PROCEDURE

Bone marrow samples obtained from 49 children with ALL were analyzed at diagnosis and at the end of induction therapy for the detection of clonal IgH, TCRdelta, and TCRgamma rearrangements by PCR. The results were compared with those obtained by standard morphologic analysis and risk group classification.

RESULTS

Patients who had clonality detected at the end of induction showed a significantly higher recurrence rate and lower event-free survival than those without detected clonality (24.9% vs. 89.7%) (P < 0.0001). Multivariate analysis revealed that detection of clonality at the end of induction was the most important, independent prognostic factor when associated with age, number of white blood cells, and immunophenotyping.

CONCLUSIONS

PCR detection of clonality using consensus primers is a relatively simple technique that is able to identify patients with a high chance of recurrence, and shows a higher sensitivity and a better prognostic value than standard morphologic analysis and risk group classification, defining a new remission criterion. However, further multicentric prospective studies using this technique employing a larger number of cases are necessary to confirm these findings.

Intermediate-dose methotrexate and intravenous 6-mercaptopurine chemotherapy for children with acute lymphoblastic leukemia who did not respond to initial induction therapy

PURPOSE

To determine the complete remission rate of children with acute lymphoblastic leukemia (ALL) who were not induced into remission by initial therapy, when subsequently treated with intermediate-dose methotrexate and intravenous 6-mercaptopurine.

PATIENTS AND METHODS

Children with B-precursor ALL who did not achieve initial remission after 4 or 6 weeks of standard three- or four-drug induction chemotherapy were entered on study. Therapy consisted of three doses at weekly intervals of methotrexate 1,000 mg/m2 over 24 hours followed by 6-mercaptopurine 1,000 mg/m2 over 8 hours 20 minutes. Patients achieving a partial remission could receive two additional weekly courses of methotrexate and 6-mercaptopurine. Initially, patients received weekly intrathecal chemotherapy, but the study was amended to include intrathecal therapy only at week 1.

RESULTS

Nineteen patients were entered on study. All were evaluable for toxicity and response. There were seven complete remissions, four partial remissions, six patients with no response, and two children with progressive disease, for an overall complete remission rate of 37%. One patient was removed from the study after the second course of methotrexate and 6-mercaptopurine because of renal failure. Two patients had neurologic toxicity resulting in a study amendment. No patients subsequently experienced neurologic toxicity.

CONCLUSIONS

Intermediate-dose intravenous methotrexate and intravenous 6-mercaptopurine can induce remission in some patients with ALL who experience initial induction failure. Features predicting complete remission, however, could not be identified.

Treatment of childhood acute lymphoblastic leukemia: results of Dana-Farber ALL Consortium Protocol 87-01

PURPOSE

To improve efficacy and reduce toxicity of treatment for children with acute lymphoblastic leukemia.

PATIENTS AND METHODS

Patients from all risk groups, including infants and those with T-cell disease, were treated between 1987 and 1991. Standard-risk (SR) patients did not receive cranial irradiation, whereas high-risk (HR) and very high-risk (VHR) patients participated in a randomized comparison of 18 Gy of cranial irradiation conventionally fractionated versus two fractions per day (hyperfractionated).

RESULTS

At a median follow-up of 9.2 years, the 9-year event-free survival (EFS +/- SE) was 75% +/- 2% for all 369 patients, 77% +/- 4% for the 142 SR patients, and 73% +/- 3% for the 227 HR/VHR patients (P =.37 comparing SR and HR/VHR). The CNS, with or without concomitant bone marrow involvement, was the first site of relapse in 19 (13%) of the 142 SR patients: 16 (20%) of 79 SR boys and three (5%) of 63 SR girls. This high incidence of relapses necessitated a recall of SR boys for additional therapy. CNS relapse occurred in only two (1%) of 227 HR and VHR patients. There were no outcome differences found among randomized treatment groups. Nine-year overall survival was 84% +/- 2% for the entire population, 93% +/- 2% for SR children, and 79% +/- 3% for HR and VHR children (P <.01 comparing SR and HR/VHR).

CONCLUSION

A high overall survival outcome was obtained for SR patients despite the high risk of CNS relapse for SR boys, which was presumed to be associated with eliminating cranial radiation without intensifying systemic or intrathecal chemotherapy. For HR/VHR patients, inability to salvage after relapse (nearly all of which were in the bone marrow) remains a significant clinical problem.

Excellent therapeutic efficacy and minimal late neurotoxicity in children treated with 18 grays of cranial radiation therapy for high-risk acute lymphoblastic leukemia: a 7-year follow-up study of the Dana-Farber Cancer Institute Consortium Protocol 87-01

BACKGROUND

In the current study, the authors evaluated late neuropsychologic effects 7 years after diagnosis and the long-term survival in a cohort of patients treated for high-risk childhood acute lymphoblastic leukemia (ALL) with cranial radiation therapy. Efficacy and toxicity were evaluated in relation to patient age at diagnosis (age < or > or = 36 months).

METHODS

Two hundred and one patients treated for high-risk ALL on the Dana-Farber Cancer Institute Consortium Protocol 87-01 were included, 147 of whom were in continuous complete disease remission and were eligible for cognitive testing. Sixty-one patients consented to undergo testing. All patients received 18 grays (Gy) of cranial radiation as a component of central nervous system treatment.

RESULTS

For all 201 patients, the 5-year overall survival (% +/- the standard error) was 82% +/- 2 and the 5-year event-free survival (% +/- the standard error) was 75% +/- 3. Only two patients developed a central nervous system recurrence. Intelligence quotient (IQ) and memory were at the expected mean for age, but performance on a complex figure drawing task was found to be reduced. Children who were age < 36 months at the time of diagnosis were found to have an IQ in the average range, but showed verbal deficits.

CONCLUSIONS

The results of the current study demonstrate excellent efficacy of therapy and relatively limited late neurotoxicity on a childhood ALL therapy protocol in which all evaluated patients had received 18 Gy of cranial radiation. Efficacious therapy that includes cranial radiation does not appear to necessarily incur a heightened risk for significant cognitive impairment.

Results of Dana-Farber Cancer Institute Consortium protocols for children with newly diagnosed acute lymphoblastic leukemia (1981-1995)

The Dana-Farber Cancer Institute (DFCI) ALL consortium has been conducting clinical trials in childhood acute lymphoblastic leukemia (ALL) since 1981. The treatment backbone has included intensive, multi-agent remission induction, early intensification with weekly, high-dose asparaginase, cranial radiation for the majority of patients, frequent vincristine/ corticosteroid pulses during post-remission therapy, and for high-risk patients, doxorubicin during intensification. Between 1981 and 1995, 1,255 children with newly diagnosed ALL were evaluated on four consecutive protocols: 81-01 (1981-1985), 85-01 (1985-1987), 87-01 (1987-1991) and 91-01 (1991-1995). The 5-year event-free survival (EFS) rates (+/- standard error) for all patients by protocol were as follows: 74 +/- 3% (81-01), 78 +/- 3% (85-01), 77 +/- 2% (87-01) and 83 +/- 2% (91-01). The 5-year EFS rates ranged from 78 to 85% for patients with B-progenitor phenotype retrospectively classified as NCI standard-risk, 63-82% for NCI high-risk B-progenitor patients, and 70-79% for patients with T cell phenotype. Results of randomized studies revealed that neither high-dose methotrexate during induction (protocol 87-01) nor high-dose 6-mercaptopurine during intensification (protocol 91-01) were associated with improvement in EFS compared with standard doses. Current studies continue to focus on improving efficacy while minimizing acute and late toxicities.

Clinical importance of minimal residual disease in childhood acute lymphoblastic leukemia

By using rapid flow cytometric techniques capable of detecting one leukemic cell in 104 normal cells, we prospectively studied minimal residual disease (MRD) in 195 children with newly diagnosed acute lymphoblastic leukemia (ALL) in clinical remission. Bone marrow aspirates (n = 629) were collected at the end of remission induction therapy and at 3 intervals thereafter. Detectable MRD (ie, ≥0.01% leukemic mononuclear cells) at each time point was associated with a higher relapse rate (P < .001); patients with high levels of MRD at the end of the induction phase (≥1%) or at week 14 of continuation therapy (≥0.1%) had a particularly poor outcome. The predictive strength of MRD remained significant even after adjusting for adverse presenting features, excluding patients at very high or very low risk of relapse from the analysis, and considering levels of peripheral blood lymphoblasts at day 7 and day 10 of induction therapy. The incidence of relapse among patients with MRD at the end of the induction phase was 68% ± 16% (SE) if they remained with MRD through week 14 of continuation therapy, compared with 7% ± 7% if MRD became undetectable (P = .035). The persistence of MRD until week 32 was highly predictive of relapse (all 4 MRD+patients relapsed vs 2 of the 8 who converted to undetectable MRD status; P = .021). Sequential monitoring of MRD by the method described here provides highly significant, independent prognostic information in children with ALL. Recent improvements in this flow cytometric assay have made it applicable to more than 90% of all new patients.

Clinical importance of minimal residual disease in childhood acute lymphoblastic leukemia

By using rapid flow cytometric techniques capable of detecting one leukemic cell in 104 normal cells, we prospectively studied minimal residual disease (MRD) in 195 children with newly diagnosed acute lymphoblastic leukemia (ALL) in clinical remission. Bone marrow aspirates (n = 629) were collected at the end of remission induction therapy and at 3 intervals thereafter. Detectable MRD (ie, ≥0.01% leukemic mononuclear cells) at each time point was associated with a higher relapse rate (P &lt; .001); patients with high levels of MRD at the end of the induction phase (≥1%) or at week 14 of continuation therapy (≥0.1%) had a particularly poor outcome. The predictive strength of MRD remained significant even after adjusting for adverse presenting features, excluding patients at very high or very low risk of relapse from the analysis, and considering levels of peripheral blood lymphoblasts at day 7 and day 10 of induction therapy. The incidence of relapse among patients with MRD at the end of the induction phase was 68% ± 16% (SE) if they remained with MRD through week 14 of continuation therapy, compared with 7% ± 7% if MRD became undetectable (P = .035). The persistence of MRD until week 32 was highly predictive of relapse (all 4 MRD+patients relapsed vs 2 of the 8 who converted to undetectable MRD status; P = .021). Sequential monitoring of MRD by the method described here provides highly significant, independent prognostic information in children with ALL. Recent improvements in this flow cytometric assay have made it applicable to more than 90% of all new patients.

New definition of remission in childhood acute lymphoblastic leukemia

The extent of clearance of leukemic cells from the blood or bone marrow during the early phase of therapy is an independent prognostic factor in acute lymphoblastic leukemia (ALL). Several methods are available to measure the minimal residual disease (MRD) remaining after initial intensive chemotherapy. The most promising are flow cytometric detection of aberrant immunophenotypes and polymerase chain reaction analysis of clonal antigen-receptor gene rearrangements. When applied together, these techniques enable one to monitor MRD in virtually all cases of ALL. Patients who achieve an 'immunologic' or 'molecular' remission (ie leukemic involvement of <0.01% of nucleated bone marrow cells at the end of remission induction therapy) are predicted to have a better clinical outcome than patients whose remission is defined solely by morphologic criteria. In studies to date, patients with MRD at a level of 10(-2) or more at the end of induction have fared almost as poorly as those with > or =5% blast cells in the bone marrow (ie induction failures). Sequential monitoring of MRD can improve the clinical utility of risk assessment still further. Additional studies are needed to determine the critical levels of MRD at various times of treatment and whether therapeutic intervention based on MRD findings can improve clinical outcome.

Outcome of treatment in children with Philadelphia chromosome-positive acute lymphoblastic leukemia

BACKGROUND

Children with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL) have a poor prognosis, and there is no consensus on the optimal treatment for this variant of ALL.

METHODS

We reviewed the medical records of patients with Ph-positive ALL who were treated with intensive chemotherapy, with or without bone marrow transplantation, by 10 study groups or large single institutions from 1986 to 1996. Data on 326 children and young adults, who ranged in age from 0.4 to 19.9 years (median, 8.1), were analyzed to determine the rate of complete remission and the probability of event-free, disease-free and overall survival according to standard prognostic factors and type of treatment.

RESULTS

The 267 patients who achieved a complete remission after induction chemotherapy (82 percent) were stratified into three subgroups according to the age and leukocyte count at the time of diagnosis: those with the best prognosis (a leukocyte count of less than 50,000 per cubic millimeter and an age of less than 10 years; 95 patients); those with an intermediate prognosis (intermediate-risk features; 92 patients); and those with the worst prognosis (a leukocyte count of more than 100,000 per cubic millimeter; 80 patients). The estimates of disease-free survival at five years (+/-SE) were 49+/-5 percent) for patients with the best prognosis), 30+/-5 percent (for those with an intermediate prognosis), and 20+/-5 percent (for those with the worst prognosis) (P<0.001 for the overall comparison). We also found that transplantation of bone marrow from an HLA-matched related donor offered significantly greater benefit than intensive chemotherapy alone in terms of protecting patients from relapse or other adverse events (relative risk, 0.3; 95 percent confidence interval, 0.2 to 0.5; P<0.001). This finding was consistent in all three groups.

CONCLUSIONS

Unlike the usual type of all, Ph-positive ALL is associated with a poor prognosis. Nevertheless, in some patients with favorable prognosis features, the disease can be be controlled by intensive chemotherapy. Transplantation of bone marrow from an HLA-matched related donor is superior to other types of transplantation and to intensive chemotherapy alone in prolonging initial complete remissions.

Acute lymphoblastic leukemia in children

As the overall long-term event-free survival rate in children with acute lymphoblastic leukemia approaches 80%, emphasis is being placed on risk-directed therapy so that patients are neither overtreated nor undertreated. It has become apparent that a risk assignment system based on primary genetic abnormalities is inadequate by itself. For example, leukemias with the MLL-AF4 or BCR-ABL fusion gene are, in fact, heterogeneous diseases. Many require allogeneic hematopoietic stem-cell transplantation; some, if the patient is of favorable age and has a low presenting leukocyte count, can be cured with chemotherapy alone. Measurement of early responses to therapy and extent of minimal residual disease can greatly improve the accuracy of risk assessment. Consideration of the variable effects of therapy on the prognostic significance of specific genetic abnormalities is also important. Therefore, TEL-AML1 fusion confers a favorable prognosis in some protocols of chemotherapy but not in others. Studies to identify genetic polymorphisms with pharmacokinetic and pharmacodynamic significance promise to guide further refinement of treatment strategies. This will allow maximization of anticancer effects without induction of unacceptable toxicity in individual patients.