Treatment of infants with lymphoblastic leukaemia: results of the UK Infant Protocols 1987-1999

Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is a haematological malignancy characterized by the uncontrolled proliferation of immature lymphoid cells. Over past decades, significant progress has been made in understanding the biology of ALL, resulting in remarkable improvements in its diagnosis, treatment and monitoring. Since the advent of chemotherapy, ALL has been the platform to test for innovative approaches applicable to cancer in general. For example, the advent of omics medicine has led to a deeper understanding of the molecular and genetic features that underpin ALL. Innovations in genomic profiling techniques have identified specific genetic alterations and mutations that drive ALL, inspiring new therapies. Targeted agents, such as tyrosine kinase inhibitors and immunotherapies, have shown promising results in subgroups of patients while minimizing adverse effects. Furthermore, the development of chimeric antigen receptor T cell therapy represents a breakthrough in ALL treatment, resulting in remarkable responses and potential long-term remissions. Advances are not limited to treatment modalities alone. Measurable residual disease monitoring and ex vivo drug response profiling screening have provided earlier detection of disease relapse and identification of exceptional responders, enabling clinicians to adjust treatment strategies for individual patients. Decades of supportive and prophylactic care have improved the management of treatment-related complications, enhancing the quality of life for patients with ALL.

Pharmacokinetics of PEGasparaginase in Infants with Acute Lymphoblastic Leukemia

BACKGROUND

PEGasparaginase is known to be a critical drug for treating pediatric acute lymphoblastic leukemia (ALL), however, there is insufficient evidence to determine the optimal dose for infants who are less than one year of age at diagnosis. This international study was conducted to identify the pharmacokinetics of PEGasparaginase in infants with newly diagnosed ALL and gather insight into the clearance and dosing of this population.

METHODS

Infants with ALL who received treatment with PEGasparaginase were included in our population pharmacokinetic assessment employing non-linear mixed effects modelling (NONMEM).

RESULTS

68 infants with ALL, with a total of 388 asparaginase activity samples, were included. PEGasparaginase doses ranging from 400 to 3,663 IU/m2 were administered either intravenously or intramuscularly. A one-compartment model with time-dependent clearance, modeled using a transit model, provided the best fit to the data. Body weight was significantly correlated with clearance and volume of distribution. The final model estimated a half-life of 11.7 days just after administration, which decreased to 1.8 days 14 days after administration. Clearance was 19.5% lower during the post-induction treatment phase compared to induction.

CONCLUSION

The pharmacokinetics of PEGasparaginase in infants diagnosed under one year of age with ALL is comparable to that of older children (1-18 years). We recommend a PEGasparaginase dosing at 1,500 IU/m2 for infants without dose adaptations according to age, and implementing therapeutic drug monitoring as standard practice.

Excess morbidity and mortality among survivors of childhood acute lymphoblastic leukaemia: 25 years of follow-up from the United Kingdom Childhood Cancer Study (UKCCS) population-based matched cohort

OBJECTIVES

To examine morbidity and mortality among teenagers and young adults (TYAs) previously diagnosed with acute lymphoblastic leukaemia (ALL) in childhood, and compare to the general TYA population.

DESIGN

National population-based sex-matched and age-matched case-control study converted into a matched cohort, with follow-up linkage to administrative healthcare databases.

SETTING

The study population comprised all children (0-14 years) registered for primary care with the National Health Service (NHS) in England 1992-1996.

PARTICIPANTS

1082 5-year survivors of ALL diagnosed<15 years of age (1992-1996) and 2018 unaffected individuals; followed up to 15 March 2020.

MAIN OUTCOME MEASURES

Associations with hospital activity, cancer and mortality were assessed using incidence rate ratios (IRR) and differences.

RESULTS

Mortality in the 5-year ALL survivor cohort was 20 times higher than in the comparison cohort (rate ratio 21.3, 95% CI 11.2 to 45.6), and cancer incidence 10 times higher (IRR 9.9 95% CI 4.1 to 29.1). Hospital activity was increased for many clinical specialties, the strongest associations being for endocrinology; outpatient IRR 36.7, 95% CI 17.3 to 93.4 and inpatient 19.7, 95% CI 7.9 to 63.2 for males, and 11.0, 95% CI 6.2 to 21.1 and 6.2 95% CI 3.1 to 13.5, respectively, for females. Notable excesses were also evident for cardiology, neurology, ophthalmology, respiratory medicine and general medicine. Males were also more likely to attend gastroenterology; ear, nose and throat; urology; and dermatology, while females were more likely to be seen in plastic surgery and less likely in midwifery.

CONCLUSIONS

Adding to excess risks of death and cancer, survivors of childhood ALL experience excess outpatient and inpatient activity across their TYA years, which is not related to routine follow-up monitoring. Involving most clinical specialties, associations are striking, showing no signs of diminishing over time. Recognising that all survivors are potentially at risk of late treatment-associated effects, our findings underscore the need to take prior ALL diagnosis into account when interpreting seemingly unrelated symptoms later in life.

Presentation acuity, induction mortality, and resource utilization in infants with acute leukemia

BACKGROUND

Treatment of infants with acute leukemia remains challenging, especially for acute lymphocytic leukemia (ALL). Infants have shown markedly higher rates of induction mortality compared with noninfants. There are limited data on presentation acuity and supportive care utilization in this age group.

METHODS

In retrospective analyses of patients treated for new onset ALL or acute myeloid leukemia (AML) at pediatric hospitals contributing to the Pediatric Health Information System, we compared presentation acuity, induction mortality, and resource utilization in infants relative to noninfants less than 10 years at diagnosis.

RESULTS

Analyses included 10 359 children with ALL (405 infants, 9954 noninfants) and 871 AML (189 infants, 682 noninfants). Infants were more likely to present with multisystem organ failure compared to noninfants for both ALL (12% and 1%, PR = 10.8, 95% CI: 7.4, 15.7) and AML (6% vs. 3%; PR = 2.0, 95% CI: 1.0, 3.7). Infants with ALL had higher induction mortality compared to noninfants, even after accounting for differences in anthracycline exposure and presentation acuity (2.7% vs. 0.5%, HR = 2.1, 95% CI: 1.0, 4.8). Conversely, infants and noninfants with AML had similar rates of induction mortality (3.2% vs. 2.1%, HR = 1.2, 95% CI: 0.3, 3.9), which were comparable to rates among infants with ALL. Infants with ALL and AML had greater requirements for blood products, diuretics, supplemental oxygen, and ventilation during induction relative to noninfants.

CONCLUSIONS

Infants with leukemia present with higher acuity compared with noninfants. Induction mortality and supportive care requirements for infants with ALL were similar to all children with AML, and significantly higher than those for noninfants with ALL.

Acute Leukemia in Infants

PURPOSE OF THE REVIEW

Infant leukemia is a rare, distinct subgroup of pediatric acute leukemias diagnosed in children under 1 year of age and characterized by unique, aggressive biology. Here, we review its clinical presentation, underlying molecular biology, current treatment strategies, and novel therapeutic approaches.

RECENT FINDINGS

Infant leukemias are associated with high-risk molecular features and high rates of chemotherapy resistance. International collaborative clinical trials have led to better understanding of the underlying molecular biology, refined risk-based stratification, and investigated the use of hematopoietic stem cell transplantation. However, intensification of chemotherapy has failed to improve outcomes, and current regimens are associated with significant treatment-related and long-term toxicities. Infants with leukemia remain a challenging group to treat. We must continue collaborative efforts to move beyond traditional cytotoxic chemotherapy, incorporate molecularly targeted strategies and immunotherapy, and increase access to clinical trials to improve outcomes for this high-risk group of patients.

MLL-Rearranged Acute Leukemia with t(4;11)(q21;q23)-Current Treatment Options. Is There a Role for CAR-T Cell Therapy?

The MLL (mixed-lineage leukemia) gene, located on chromosome 11q23, is involved in chromosomal translocations in a subtype of acute leukemia, which represents approximately 10% of acute lymphoblastic leukemia and 2.8% of acute myeloid leukemia cases. These translocations form fusions with various genes, of which more than 80 partner genes for MLL have been identified. The most recurrent fusion partner in MLL rearrangements (MLL-r) is AF4, mapping at chromosome 4q21, accounting for approximately 36% of MLL-r leukemia and particularly prevalent in MLL-r acute lymphoblastic leukemia (ALL) cases (57%). MLL-r leukemia is associated with a sudden onset, aggressive progression, and notoriously poor prognosis in comparison to non-MLL-r leukemias. Despite modern chemotherapeutic interventions and the use of hematopoietic stem cell transplantations, infants, children, and adults with MLL-r leukemia generally have poor prognosis and response to these treatments. Based on the frequency of patients who relapse, do not achieve complete remission, or have brief event-free survival, there is a clear clinical need for a new effective therapy. In this review, we outline the current therapy options for MLL-r patients and the potential application of CAR-T therapy.

MLL-Rearranged Leukemias-An Update on Science and Clinical Approaches

The mixed-lineage leukemia 1 (MLL1) gene (now renamed Lysine [K]-specific MethylTransferase 2A or KMT2A) on chromosome 11q23 is disrupted in a unique group of acute leukemias. More than 80 different partner genes in these fusions have been described, although the majority of leukemias result from MLL1 fusions with one of about six common partner genes. Approximately 10% of all leukemias harbor MLL1 translocations. Of these, two patient populations comprise the majority of cases: patients younger than 1 year of age at diagnosis (primarily acute lymphoblastic leukemias) and young- to-middle-aged adults (primarily acute myeloid leukemias). A much rarer subgroup of patients with MLL1 rearrangements develop leukemia that is attributable to prior treatment with certain chemotherapeutic agents-so-called therapy-related leukemias. In general, outcomes for all of these patients remain poor when compared to patients with non-MLL1 rearranged leukemias. In this review, we will discuss the normal biological roles of MLL1 and its fusion partners, how these roles are hypothesized to be dysregulated in the context of MLL1 rearrangements, and the clinical manifestations of this group of leukemias. We will go on to discuss the progress in clinical management and promising new avenues of research, which may lead to more effective targeted therapies for affected patients.

Orbital mass secondary to infantile acute lymphoblastic leukaemia

An 8-month-old Asian infant girl was referred with a 1-week history of left periorbital swelling on a background of a narrowed left palpebral aperture over the preceding 8 weeks. There was no history of chronic illness, fever or other systemic features. Examination revealed a tender and fluctuant medial canthal swelling with associated periorbital haematoma. There were no other ophthalmic findings and neurological examination was normal. A MRI scan of the brain and orbit demonstrated abnormal soft tissue with features of an aggressive tumour in the left orbital region with no globe invasion. Peripheral blood smear revealed blast cells, confirmed by bone marrow aspirate. A diagnosis of infant acute lymphoblastic leukaemia was made. The patient was started on risk-stratified chemotherapy according to the Interfant-06 Protocol The periorbital swelling resolved by day eight following a course of prednisolone, the patient continues on chemotherapy and is currently in molecular remission.

B-cell acute lymphoblastic leukemia with mature phenotype and MLL rearrangement: report of five new cases and review of the literature

The association between mature-B phenotype and MLL abnormalities in acute lymphoblastic leukemia (ALL) is a very unusual finding; only 14 pediatric cases have been reported so far. We describe the clinical and biological characteristics and outcome of five pediatric cases of newly diagnosed B lineage ALL with MLL abnormalities and mature immunophenotype based on light chain restriction and surface Ig expression. Blasts showed variable expression of CD10/CD34/TdT. MLL abnormalities with no MYC involvement were detected in all patients by G-banding, FISH, and/or RT-PCR. Three patients were treated according to Interfant protocol, one to ALLIC-09, and one received B-NHL-BFM-2004. All patients achieved complete remission and three of them relapsed. Despite the small cohort size, it could be postulated that B lineage ALL with MLL abnormalities and mature phenotype is a distinct entity that differs both from the typical Pro B ALL observed in infants and mature B-ALL with high MYC expression.

[Infant acute leukemia]

If acute leukemia is the most frequent cancer in childhood (33%), it remains a very rare diagnosis in infants less than one year old, e.g. less than 5% of cases. At this age, the frequency of acute lymphoblastic leukemia (ALL) (almost all of B-lineage) is quite similar to the one of myeloblastic forms (AML). Infant leukemia frequently presents with high hyperleucocytosis, major tumoral burden and numerous extra-hematological features, especially in central nervous system and skin. Whatever the lineage, the leukemic cell is often very immature cytologically and immunologically. Rearrangements of the Mixed Lineage Leukemia (MLL) gene, located on band 11q23, are the hallmark of these immature leukemias and confer a particular resistance to conventional approaches, corticosteroids and chemotherapy. The immaturity of infants less than 1-year-old is associated to a decrease of the tolerable dose-intensity of some drugs (anthracyclines, alkylating agents) or asks questions about some procedures like radiotherapy or high dose conditioning regimen, responsible of inacceptable acute and late toxicities. The high level of severe infectious diseases and other high-grade side effects limits also the capacity to cure these infants. The survival of infants less than 1-year-old with AML is only 50% but similar to older children. On the other hand, survival of those with ALL is the same, then quite limited comparing the 80% survival in children over one year. Allogeneic stem cell transplantations are indicated in high-risk subgroups of infant ALL (age below 6 months, high hyperleucocytosis >300.10(9)/L, MLL-rearrangement, initial poor prednisone response). However, morbidity and mortality remain very important and these approaches cannot be extended to all cases. During the neonatal period, the dismal prognosis linked to the high number of primary failures or very early relapses and uncertainties about the late toxicities question physicians about ethics. It is an emergency to propose different strategies (targeted therapies) to these infants with acute leukemia as conventional trials failed to improve outcome.

The evolution of clinical trials for infant acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) in infants has a significantly inferior outcome in comparison with older children. Despite initial improvements in survival of infants with ALL since establishment of the first pediatric cooperative group ALL trials, the poor outcome has plateaued in recent years. Historically, infants were treated on risk-adapted childhood ALL protocols. These studies were pivotal in identifying the need for infant-specific protocols, delineating prognostic categories and the requirement for a more unified approach between study groups to overcome limitations in accrual because of low incidence. This subsequently led to the development of collaborative infant-specific studies. Landmark outcomes have included the elimination of cranial radiotherapy following the discovery of intrathecal and high-dose systemic therapy as a superior and effective treatment strategy for central nervous system disease prophylaxis, with improved neurodevelopmental outcome. Universal prospective identification of independent adverse prognostic factors, including presence of a mixed lineage leukemia rearrangement and young age, has established the basis for risk stratification within current trials. The infant-specific trials have defined limits to which conventional chemotherapeutic agents can be intensified to optimize the balance between treatment efficacy and toxicity. Despite variations in therapeutic intensity, there has been no recent improvement in survival due to the equilibrium between relapse and toxicity. Ultimately, to improve the outcome for infants with ALL, key areas still to be addressed include identification and adaptation of novel prognostic markers and innovative therapies, establishing the role of hematopoietic stem cell transplantation in first complete remission, treatment strategies for relapsed/refractory disease and monitoring and timely intervention of late effects in survivors. This would be best achieved through a single unified international trial.

Acute lymphoblastic leukemia in children with Down syndrome: a retrospective analysis from the Ponte di Legno study group

Children with Down syndrome (DS) have an increased risk of B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). The prognostic factors and outcome of DS-ALL patients treated in contemporary protocols are uncertain. We studied 653 DS-ALL patients enrolled in 16 international trials from 1995 to 2004. Non-DS BCP-ALL patients from the Dutch Child Oncology Group and Berlin-Frankfurt-Münster were reference cohorts. DS-ALL patients had a higher 8-year cumulative incidence of relapse (26% ± 2% vs 15% ± 1%, P < .001) and 2-year treatment-related mortality (TRM) (7% ± 1% vs 2.0% ± <1%, P < .0001) than non-DS patients, resulting in lower 8-year event-free survival (EFS) (64% ± 2% vs 81% ± 2%, P < .0001) and overall survival (74% ± 2% vs 89% ± 1%, P < .0001). Independent favorable prognostic factors include age <6 years (hazard ratio [HR] = 0.58, P = .002), white blood cell (WBC) count <10 × 10(9)/L (HR = 0.60, P = .005), and ETV6-RUNX1 (HR = 0.14, P = .006) for EFS and age (HR = 0.48, P < .001), ETV6-RUNX1 (HR = 0.1, P = .016) and high hyperdiploidy (HeH) (HR = 0.29, P = .04) for relapse-free survival. TRM was the major cause of death in ETV6-RUNX1 and HeH DS-ALLs. Thus, while relapse is the main contributor to poorer survival in DS-ALL, infection-associated TRM was increased in all protocol elements, unrelated to treatment phase or regimen. Future strategies to improve outcome in DS-ALL should include improved supportive care throughout therapy and reduction of therapy in newly identified good-prognosis subgroups.

Does hematopoietic stem cell transplantation benefit infants with acute leukemia?

A 6-month-old girl was diagnosed with acute lymphoblastic leukemia (ALL). She has completed induction therapy and is currently in first complete remission (CR1). You are asked by your resident if hematopoietic stem cell transplantation (HSCT) would benefit infants with acute leukemia.

Population survival from childhood cancer in Britain during 1978-2005 by eras of entry to clinical trials

BACKGROUND

Inclusion in clinical trials is generally viewed as best practice for most newly diagnosed childhood cancers, but the impact on population-based survival has rarely been examined.

PATIENTS AND METHODS

The population-based data were analysed for 25 853 children (66% of all registered childhood cancers) diagnosed in Britain during 1978-2005 with acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML), Hodgkin lymphoma, non-Hodgkin lymphoma, medulloblastoma, neuroblastoma, Wilms tumour, hepatoblastoma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma and germ-cell tumours. The Kaplan-Meier survival curves were compared by log-rank tests. Time trends were analysed by Cox regression. Separate analyses were done for children with ALL, medulloblastoma and neuroblastoma according to clinically relevant age thresholds.

RESULTS

Survival increased significantly during 1978-2005 for every diagnostic category; the annual reduction in risk of death ranged from 2.7% (rhabdomyosarcoma) to 12.0% (gonadal germ-cell tumours). Survival increased steadily between trial eras for ALL (age 1-14 years) and neuroblastoma (age 1-14 years), but changed little since the mid-1980s for medulloblastoma (age 0-2 years), osteosarcoma or Ewing sarcoma.

CONCLUSIONS

Changes in survival between trial eras parallel those reported by the relevant clinical trials. The increasing level of participation in trials, facilitated by the organisation of specialist care, has underpinned the substantial improvements in survival seen at the population level.

Analysis of the role of hematopoietic stem-cell transplantation in infants with acute lymphoblastic leukemia in first remission and MLL gene rearrangements: a report from the Children's Oncology Group

PURPOSE

Although the majority of children with acute lymphoblastic leukemia (ALL) are cured with current therapy, the event-free survival (EFS) of infants with ALL, particularly those with mixed lineage leukemia (MLL) gene rearrangements, is only 30% to 40%. Relapse has been the major source of treatment failure for these patients. The parallel Children's Cancer Group (CCG) 1953 and Pediatric Oncology Group (POG) 9407 studies were designed to test the hypothesis that more intensive therapy, including dose intensification of chemotherapy, and hematopoietic stem-cell transplantation (HSCT) would improve the outcome for this group of patients.

PATIENTS AND METHODS

One hundred eighty-nine infants (CCG 1953, n = 115; POG 9407, n = 74) were enrolled between October 1996 and August 2000. For infants with the MLL gene rearrangement and an appropriate donor, HSCT was the preferred treatment on CCG 1953 and investigator option on POG 9407 after completion of the second phase of therapy. Fifty-three infants underwent HSCT.

RESULTS

The 5-year EFS rate was 48.8% (95% CI, 33.9% to 63.7%) in patients who received HSCT and 48.7% (95% CI, 33.8% to 63.6%) in patients treated with chemotherapy alone (P = .60). Transplantation outcomes were not affected by the preparatory regimen or donor source.

CONCLUSION

Our data suggest that routine use of HSCT for infants with MLL-rearranged ALL is not indicated. However, limited by small numbers, this study should not be considered the definitive answer to this question.

CD22 EXON 12 deletion as a pathogenic mechanism of human B-precursor leukemia

Here, we report that primary leukemic cells from infants with newly diagnosed B-precursor leukemia express a truncated and functionally defective CD22 coreceptor protein that is unable to transmit apoptotic signals because it lacks most of the intracellular domain, including the key regulatory signal transduction elements and all of the cytoplasmic tyrosine residues. Expression of this structurally and functionally abnormal CD22 protein is associated with a very aggressive in vivo growth of patients' primary leukemia cells causing disseminated overt leukemia in SCID mice. The abnormal CD22 coreceptor is encoded by a profoundly aberrant mRNA arising from a splicing defect that causes the deletion of exon 12 (c.2208-c.2327) (CD22ΔE12) and results in a truncating frameshift mutation. The splicing defect is associated with multiple homozygous mutations within a 132-bp segment of the intronic sequence between exons 12 and 13. These mutations cause marked changes in the predicted secondary structures of the mutant CD22 pre-mRNA sequences that affect the target motifs for the splicing factors hnRNP-L, PTB, and PCBP that are up-regulated in infant leukemia cells. Forced expression of the mutant CD22ΔE12 protein in transgenic mice perturbs B-cell development, as evidenced by B-precursor/B-cell hyperplasia, and corrupts the regulation of gene expression, causing reduced expression levels of several genes with a tumor suppressor function. We further show that CD22ΔE12-associated unique gene expression signature is a discriminating feature of newly diagnosed infant leukemia patients. These striking findings implicate CD22ΔE12 as a previously undescribed pathogenic mechanism in human B-precursor leukemia.

Improved outcome with hematopoietic stem cell transplantation in a poor prognostic subgroup of infants with mixed-lineage-leukemia (MLL)-rearranged acute lymphoblastic leukemia: results from the Interfant-99 Study

To define a role for hematopoietic stem cell transplantation (HSCT) in infants with acute lymphoblastic leukemia and rearrangements of the mixed-lineage-leukemia gene (MLL(+)), we compared the outcome of MLL(+) patients from trial Interfant-99 who either received chemotherapy only or HSCT. Of 376 patients with a known MLL status in the trial, 297 (79%) were MLL(+). Among the 277 of 297 MLL(+) patients (93%) in first remission (CR), there appeared to be a significant difference in disease-free survival (adjusted by waiting time to HSCT) between the 37 (13%) who received HSCT and the 240 (87%) who received chemotherapy only (P = .03). However, the advantage was restricted to a subgroup with 2 additional unfavorable prognostic features: age less than 6 months and either poor response to steroids at day 8 or leukocytes more than or equal to 300 g/L. Ninety-seven of 297 MLL(+) patients (33%) had such high-risk criteria, with 87 achieving CR. In this group, HSCT was associated with a 64% reduction in the risk of failure resulting from relapse or death in CR (hazard ratio = 0.36, 95% confidence interval, 0.15-0.86). In the remaining patients, there was no advantage for HSCT over chemotherapy only. In summary, HSCT seems to be a valuable option for a subgroup of infant MLL(+) acute lymphoblastic leukemia carrying further poor prognostic factors. The trial was registered at www.clinicaltrials.gov as #NCT00015873 and at www.controlled-trials.com as #ISRCTN24251487.

Outcome of congenital acute lymphoblastic leukemia treated on the Interfant-99 protocol

Acute lymphoblastic leukemia (ALL) diagnosed in the first month of life (congenital ALL) is very rare. Although congenital ALL is often assumed to be fatal, no studies have been published on outcome except for case reports. The present study reports the outcome of 30 patients with congenital ALL treated with the uniform Interfant-99 protocol, a hybrid regimen combining ALL treatment with elements designed for treatment of acute myeloid leukemia. Congenital ALL was characterized by a higher white blood cell count and a strong trend for higher incidence of MLL rearrangements and CD10-negative B-lineage ALL compared with older infants. Induction failure rate was 13% and not significantly different from that in older infants (7%, P = .14), but relapse rate was significantly higher in congenital ALL patients (2-year cumulative incidence [SE] was 60.0 [9.3] vs 34.2 [2.3], P < .001). Two-year event-free survival and survival of congenital ALL patients treated with this protocol was 20% (SE 9.1%). Early death in complete remission and treatment delays resulting from toxicity were not different. The survival of 17% after last follow-up, combined with a toxicity profile comparable with that in older infants, justifies treating congenital ALL with curative intent. This trial was registered at www.clinicaltrials.gov as no. NCT 00015873, and at www.controlled-trials.com as no. ISRCTN24251487.

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.

Molecular mechanisms involved in chemoresistance in paediatric acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is the most common paediatric cancer. Despite cure rates approaching 80%, resistance to treatment and disease relapse remain a significant clinical problem. Identification of the genes and biological pathways responsible for chemoresistance is therefore crucial for the design of novel therapeutic approaches aiming to improve patient survival. Mutations in the membrane transporter P-glycoprotein genes, genetic variations in drug-metabolising enzymes and defects in apoptotic pathways are mechanisms of chemoresistance common to a wide spectrum of cancers and also play a role in paediatric ALL. In addition, several recent microarray studies have identified transcriptional profiles specifically associated with chemoresistance and pointed to a number of potentially novel therapeutic targets. These microarray studies have shown that genes discriminating between clinically responsive and resistant leukaemias tend to be involved in cellular processes such as regulation of cell cycle, proliferation, and DNA repair. Here we review the outcomes of these microarray studies and also present our own investigations into apoptotic resistance to DNA double strand breaks (DSBs) in paediatric ALL. We present stratification of paediatric ALL by the profile of DNA damage response following ionising radiation (IR) in vitro. This approach allows classification of ALL tumours at presentation into IR-apoptotic sensitive and IR-apoptotic resistant. Furthermore, apoptotic resistant leukaemias exhibit abnormal response of NFkB pathway following irradiation and inhibition of this pathway can sensitise leukaemic cells to IR-induced DSBs.

Fms-like tyrosine kinase 3 ligand stimulation induces MLL-rearranged leukemia cells into quiescence resistant to antileukemic agents

Fms-like tyrosine kinase 3 (FLT3) is highly expressed in acute lymphoblastic leukemia with the mixed-lineage leukemia (MLL) gene rearrangement refractory to chemotherapy. We examined the biological effect of FLT3-ligand (FL) on 18 B-precursor leukemic cell lines with variable karyotypic abnormalities, and found that nine of nine MLL-rearranged cell lines with wild-type FLT3, in contrast to other leukemic cell lines, are significantly inhibited in their proliferation in a dose-dependent manner by FL. This inhibition was due to induction of the G0-G1 arrest. A marked up-regulation of p27 by suppression of its protein degradation and an abrogation of constitutive signal transducers and activators of transcription 5 phosphorylation were revealed in arrested leukemia cells after FL stimulation. Importantly, FL treatment rendered not only cell lines but also primary leukemia cells with MLL rearrangement resistant to chemotherapeutic agents. MLL-rearranged leukemia cells adhering to the bone marrow stromal cell line, which expresses FL as the membrane-bound form, were induced to quiescent state resistant to chemotherapeutic agents, but their chemosensitivity was significantly restored in the presence of neutralizing anti-FL antibody. The FL/FLT3 interaction between leukemia cells and bone marrow stromal cells expressing FL at high levels should contribute, at least in part, to persistent minimal-residual disease of MLL-rearranged leukemia in bone marrow.

Acute lymphoblastic leukemia in infancy

Infant ALL is uncommon, biologically distinctive from the disease in older children, and associated with a relatively poor prognosis. Adverse prognostic factors include the presence of an MLL gene rearrangement (observed in up to 80% of infants with ALL), younger age at diagnosis, high presenting leukocyte counts, and slow early response to therapy. The role of stem cell transplant in first remission remains controversial. Current research efforts to improve the outcome of MLL-rearranged ALL in infants include clinical trials testing cytarabine-intensive regimens and translational investigations of novel, targeted therapies, such as FLT3-inhibitors.

Insights from clinical studies into the role of the MLL gene in infant and childhood leukemia

Translocations involving the Mixed Lineage Leukemia (MLL) gene at 11q23 are found in both acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML), but have different prognostic implications depending on the phenotype of the leukemia in de novo pediatric cases. The majority of MLL gene rearrangements are associated with infant ALL, and their presence predicts a poor prognosis which worsens with earlier age of presentation. Rearrangements of the MLL gene are found in most cases of infant AML and regardless of age confer an intermediate risk. The treatment of MLL-rearranged ALL in children involves increased intensification of chemotherapy, and infants with ALL are treated with an intensive regimen of ALL- and AML-like chemotherapy, with the proportion of MLL-rearranged cases being responsible for the poor outcome in this age group. The use of DNA microarray analysis to distinguish a particular gene signature for MLL-rearranged leukemias is shedding light on the molecular mechanisms and potential therapeutic targets of these leukemias. It may also prove to have a useful role in both diagnosis and prognosis. This review considers recent advances in our understanding of the role of MLL gene rearrangements in pediatric clinical practice.

Outcome of risk-based therapy for infant acute lymphoblastic leukemia with or without an MLL gene rearrangement, with emphasis on late effects: a final report of two consecutive studies, MLL96 and MLL98, of the Japan Infant Leukemia Study Group

We evaluated the efficacy of a treatment strategy in which infants with acute lymphoblastic leukemia (ALL) were stratified by their MLL gene status and then assigned to different risk-based therapies. A total of 102 patients were registered on two consecutive multicenter trials, designated MLL96 and MLL98, between 1995 and 2001. Those with a rearranged MLL gene (MLL-R, n=80) were assigned to receive intensive chemotherapy followed by hematopoietic stem cell transplantation (HSCT), while those with germline MLL (MLL-G, n=22) were treated with chemotherapy alone. The 5-year event-free survival (EFS) rate for all 102 infants was 50.9% (95% confidence interval, 41.0-60.8%). The most prominent late effect was growth impairment, observed in 58.9% of all evaluable patients in the MLL-R group. This plan of risk-based therapy appears to have improved the overall prognosis for infants with ALL, compared with previously reported results. However, over half the events in patients with MLL rearrangement occurred before the instigation of HSCT, and that HSCT-related toxic events comprised 36.3% (8/22) of post-transplantation events, suggesting that further stratification within the MLL-R group and the development of more effective early-phase intensification chemotherapy will be needed before the full potential of this strategy is realized.

A treatment protocol for infants younger than 1 year with acute lymphoblastic leukaemia (Interfant-99): an observational study and a multicentre randomised trial

BACKGROUND

Acute lymphoblastic leukaemia in infants younger than 1 year is rare, and infants with the disease have worse outcomes than do older children. We initiated an international study to investigate the effects of a new hybrid treatment protocol with elements designed to treat both acute lymphoblastic leukaemia and acute myeloid leukaemia, and to identify any prognostic factors for outcome in infants. We also did a randomised trial to establish the value of a late intensification course.

METHODS

Patients aged 0-12 months were enrolled by 17 study groups in 22 countries between 1999 and 2005. Eligible patients were stratified for risk according to their peripheral blood response to a 7-day prednisone prophase, and then given a hybrid regimen based on the standard protocol for acute lymphoblastic leukaemia, with some elements designed for treatment of acute myeloid leukaemia. Before the maintenance phase, a subset of patients in complete remission were randomly assigned to receive either standard treatment or a more intensive chemotherapy course with high-dose cytarabine and methotrexate. The primary outcomes were event-free survival (EFS) for the initial cohort of patients and disease-free survival (DFS) for the patients randomly assigned to a treatment group. Data were analysed on an intention-to-treat basis. This trial was registered with ClinicalTrials.gov, number NCT 00015873, and at controlled-trials.com, number ISRCTN24251487.

FINDINGS

In the 482 enrolled patients who underwent hybrid treatment, 260 (58%) were in complete remission at a median follow-up of 38 (range 1-78) months, and EFS at 4 years was 47.0% (SE 2.6, 95% CI 41.9-52.1). Of 445 patients in complete remission after 5 weeks of induction treatment, 191 were randomised: 95 patients to receive a late intensification course, and 96 to a control group. At a median follow-up of 42 (range 1-73) months, 60 patients in the treatment group and 57 controls were disease-free. DFS at 4 years did not differ between the two groups (60.9% [SE 5.2] for treatment group vs 57.0% [5.5] for controls; p=0.81). During the intensification phase, of 71 patients randomly assigned to the treatment group, and for whom toxicity data were available, 35 (49%) had infections, 21 (30%) patients had mucositis, 22 (31%) patients had toxic effects on the liver, and 2 (3%) had neurotoxicity. All types of rearrangements in the (mixed lineage leukaemia) MLL gene, very high white blood cell count, age of younger than 6 months, and a poor response to the prednisone prophase were independently associated with inferior outcomes.

INTERPRETATION

Patients treated with our hybrid protocol, and especially those who responded poorly to prednisone, had higher EFS than most reported outcomes for treatment of infant ALL. Delayed intensification of chemotherapy did not benefit patients.

Favorable outcome for infant acute lymphoblastic leukemia after hematopoietic stem cell transplantation

Infants with acute lymphoblastic leukemia (ALL) have a poor prognosis when treated with standard chemotherapy. A subset of these infants, particularly those with mixed-lineage leukemia (MLL) rearrangements, has a high likelihood of relapse. Hematopoietic stem cell transplantation (HSCT) performed early in first remission may improve outcome. We present the results of 16 patients with infant ALL who were treated with HSCT in first remission. Six patients were < or =6 months of age at diagnosis, 11 had an initial white blood cell count of >50000/microL, and all patients with determinable cytogenetics had a high-risk karyotype [t(4:11) abnormality or other MLL rearrangement]. All patients received 150 cGy of total body irradiation for 8 doses (1200 cGy). Fifteen of 16 patients received etoposide at 1000 mg/m(2) as a continuous infusion over 24 hours and cyclophosphamide at 60 mg/kg/d for 3 days. Eight patients received HSCT from an HLA-identical sibling, and 8, from unrelated cord blood. Twelve (75%) patients remain long-term survivors (median follow-up, 4.7 years). Two patients, 1 of whom had minimal residual disease at HSCT, died after relapse following HSCT. Two patients died of transplant-related causes. The HSCT was well tolerated; 15 patients achieved neutrophil engraftment at a median of 16 days. Acute and chronic graft-versus-host disease were minimal in these patients. These results support the use of HSCT in the treatment of infant ALL, especially when used as consolidation in first remission. The risk of relapse seems to be decreased with this approach. Further work is being performed to determine the long-term effects from this therapy.

Analysis of prognostic factors of acute lymphoblastic leukemia in infants: report on CCG 1953 from the Children's Oncology Group

Infant acute lymphoblastic leukemia (ALL) has a poor therapeutic outcome despite attempts to treat it based on prognostic factor-guided therapy. This is the first cooperative group trial characterizing all infants at the molecular level for MLL/11q23 rearrangement. All infants enrolled on Children's Cancer Group (CCG) 1953 were tested for MLL rearrangement by Southern blot and the 11q23 translocation partner was identified (4;11, 9;11, 11;19, or "other") by reverse-transcriptase polymerase chain reaction (PCR). One hundred fifteen infants were enrolled; overall event-free survival (EFS) was 41.7% (SD = 9.2%) and overall survival (OS) was 44.8% at 5 years. Five-year EFS for MLL-rearranged cases was 33.6% and for MLL-nonrearranged cases was 60.3%. The difference in EFS between the 3 major MLL rearrangements did not reach statistical significance. Multivariate Cox regression analyses showed a rank order of significance for negative impact on prognosis of CD10 negativity, age younger than 6 months, and MLL rearrangement, in that order. Toxicity was the most frequent cause of death. Relapse as a first event in CCG 1953 was later (median, 295 days) compared with CCG 1883 historic control (median, 207 days). MLL/11q23 rearrangement, CD10 expression, and age are important prognostic factors in infant ALL, but molecular 11q23 translocation partners do not predict outcome.

Towards targeted therapy for infant acute lymphoblastic leukaemia

Despite the greatly improved treatment regimes for childhood acute lymphoblastic leukaemia (ALL) in general, resulting in long-term survival in approximately 80% of cases, current therapies still fail in >50% of ALL cases diagnosed within the first year of life (i.e. in infants). Therefore, more adequate treatment strategies are urgently needed to also improve the prognosis for these very young patients with ALL. Here we review the current acquaintance with the biology of infant ALL and describe how this knowledge may lead to innovative therapeutic approaches.

Comparable Long-Term Survival After Unrelated and HLA-Matched Sibling Donor Hematopoietic Stem Cell Transplantations for Acute Leukemia in Children Younger Than 18 Months

Purpose

To describe outcomes after unrelated donor stem cell transplantation (HCT) in children (< 18 months at diagnosis) with acute leukemia and compare these with outcomes after human leukocyte antigen (HLA)-matched sibling donor HCT.

Patients and Methods

We compared the results of unrelated donor HCT with bone marrow (n = 85) or cord blood grafts (n = 81) and HLA-matched sibling donor HCT with bone marrow grafts (n = 101) for acute myeloid or acute lymphoblastic leukemia using Cox proportional hazards models. Unrelated donor HCT recipients were younger, more likely to have MLL gene rearrangement, to have advanced leukemia, and to receive irradiation before HCT.

Results

Treatment-related mortality rates were 6%, 15%, and 31% after matched sibling, unrelated donor bone marrow, and cord blood HCT, respectively. Risks of relapse, overall and leukemia-free survival were significantly associated with disease status at transplantation. Though leukemia recurrence was lowest after unrelated donor HCT in first clinical remission (CR), overall survival, and leukemia-free survival rates were similar after matched sibling and unrelated donor HCT, after adjustment for disease status. Relapse, overall and leukemia-free survival did not differ by graft type (bone marrow v cord blood) or type of leukemia. Three-year probabilities of leukemia-free survival were 49% and 54% after HLA-matched sibling and unrelated donor transplantation in first CR, respectively. Corresponding rates for those with advanced leukemia were 20% and 30%.

Conclusion

Unrelated donor HCT should be considered for infants with acute leukemia in first CR using the same eligibility criteria as are currently used for those with HLA matched sibling donors.

Individualized therapy for childhood acute lymphoblastic leukemia

In the field of oncology, a growing emphasis is now being placed on individualizing treatment in a way that maximizes chance for cure while minimizing unwanted side effects. In childhood acute lymphoblastic leukemia (ALL), several well-established clinical and biologic prognostic variables have traditionally been used to risk stratify therapy for individual patients. While this approach has been very successful, many relapses still occur unpredictably in patients characterized as having favorable features of their disease at diagnosis. Furthermore, it is likely that other children are overtreated. Therefore, current initiatives in childhood leukemia have focused on identifying new prognostic markers to refine treatment decision-making. Recent advances, which include the sequencing of the human genome, and technical developments in high-throughput genomics and proteomics, have facilitated these efforts. This review will chart the evolution of individualized therapy for ALL, the most common malignancy of children.

The biological and clinical significance of MLL abnormalities in haematological malignancies

The MLL (Mixed Lineage Leukaemia or Myeloid/Lymphoid Leukaemia) gene on chromosome 11q23 is frequently involved in chromosomal translocations associated with human acute leukaemias. These translocations lead to fusion genes generally resulting in novel chimeric proteins containing the amino terminus of MLL fused in-frame to one of about 30 distinct partner proteins. Abnormalities involving the MLL gene are observed in leukaemias of either lymphoid or myeloid lineage derivation, as well as in poorly differentiated or biphenotypic leukaemias. They are frequently seen in infant patients, and patients with therapy-related secondary AML following treatment with inhibitors of topoisomerase II (epipodophyllotoxins). In the majority of cases, abnormalities involving the MLL gene are associated with a very poor prognostic outcome. In this review, we will discuss some of the recent advances in MLL research resulting from biological as well as clinical studies.

Newly diagnosed childhood acute lymphoblastic leukemia: update on prognostic factors and treatment

The development of effective therapy for children with acute lymphoblastic leukemia is one of the great successes of clinical hematology andoncology. Fifty years ago, childhood acute lymphoblastic leukemia was universally fatal, but current long-term event-free survival rates are nearly 80%. Despite this improved outcome, there are still many challenges facing investigators today. In some recent clinical trials, the outcome of "high-risk" patients has approached that of "lower risk" patients, suggesting that currently applied clinical factors, such as age and presenting leukocyte count, no longer identify the 20% of newly diagnosed patients who ultimately will relapse. Additionally, therapy remains nonspecific, toxic, and sometimes lethal. As more children with acute lymphoblastic leukemia survive into adolescence and adulthood, there is a need to address the late sequelae of current therapy and to develop more leukemia-specific treatments. Promising avenues of research, which may identify biologically distinctive subsets of acute lymphoblastic leukemia and potential targets for novel therapies, include studies of minimal residual disease, lymphoblast genetics (including genetic profiling studies), and host-related pharmacogenomics.

Clinical heterogeneity in childhood acute lymphoblastic leukemia with 11q23 rearrangements

To assess the clinical heterogeneity among patients with acute lymphoblastic leukemia (ALL) and various 11q23 abnormalities, we analyzed data on 497 infants, children and young adults treated between 1983 and 1995 by 11 cooperative groups and single institutions. The substantial sample size allowed separate analyses according to age younger or older than 12 months for the various cytogenetic subsets. Infants with t(4;11) ALL had an especially dismal prognosis when their disease was characterized by a poor early response to prednisone (P=0.0005 for overall comparison; 5-year event-free survival (EFS), 0 vs 23+/-+/-12% s.e. for those with good response), or age less than 3 months (P=0.0003, 5-year EFS, 5+/-+/-5% vs 23.4+/-+/-4% for those over 3 months). A poor prednisone response also appeared to confer a worse outcome for older children with t(4;11) ALL. Hematopoietic stem cell transplantation failed to improve outcome in either age group. Among patients with t(11;19) ALL, those with a T-lineage immunophenotype, who were all over 1 year of age, had a better outcome than patients over 1 year of age with B-lineage ALL (overall comparison, P=0.065; 5-year EFS, 88+/-+/-13 vs 46+/-14%). In the heterogeneous subgroup with del(11)(q23), National Cancer Institute-Rome risk criteria based on age and leukocyte count had prognostic significance (P=0.04 for overall comparison; 5-year EFS, 64+/-+/-8% (high risk) vs 83+/-+/-6% (standard risk)). This study illustrates the marked clinical heterogeneity among and within subgroups of infants or older children with ALL and specific 11q23 abnormalities, and identifies patients at particularly high risk of failure who may benefit from innovative therapy.

Clinical features, cytogenetics and outcome in acute lymphoblastic and myeloid leukaemia of infancy: report from the MRC Childhood Leukaemia working party

The clinical features, cytogenetics and response to treatment have been examined in 180 infants (aged <1 year) with acute leukaemia; 118 with acute lymphoblastic leukaemia (ALL) and 62 with acute myeloid leukaemia (AML). Comparison of clinical features showed no difference in age or sex distribution between infants with ALL and AML but infants with ALL tended to have higher leucocyte counts at presentation. Cytogenetic abnormalities involving 11q23 were found in 66% of ALL and 35% of AML cases, the commonest, t(4;11) being found only in ALL. The other recognised 11q23 translocations were found in both types of leukaemia. Few patients had the common cytogenetic abnormalities associated with ALL in older children and few with AML had good risk abnormalities. Four year event-free survival 60% cf 30% (P = 0.001) and survival 65% cf 41% (P = 0.007) were significantly better in AML than ALL. These results were due to a lower risk of relapse 27% cf 62% at four years. Superior event-free survival was also seen in the subgroup of patients with 11q23 abnormalities and AML (55% cf 23%). The reasons for superior response in AML are unknown but may be related to the intensity of treatment, lineage of the leukaemia or other as yet unidentified factors.