Minimal residual disease-directed risk stratification using real-time quantitative PCR analysis of immunoglobulin and T-cell receptor gene rearrangements in the international multicenter trial AIEOP-BFM ALL 2000 for childhood acute lymphoblastic leukemia

Flow-cytometric minimal residual disease monitoring in blood predicts relapse risk in pediatric B-cell precursor acute lymphoblastic leukemia in trial AIEOP-BFM-ALL 2000

BACKGROUND

Flow-cytometric monitoring of minimal residual disease (MRD) in bone marrow (BM) during induction of pediatric patients with acute lymphoblastic leukemia (ALL) is widely used for outcome prognostication and treatment stratification. Utilizing peripheral blood (PB) instead of BM might be favorable, but data on its usefulness are scarce.

PROCEDURE

We investigated 1303 PB samples (days 0, 8, 15, 33, and 52) and 285 BMs (day 15) from 288 pediatric ALL patients treated in trial AIEOP-BFM ALL 2000. MRD was assessed by four-color flow cytometry and evaluated as relative, absolute, and kinetic result.

RESULTS

In B-ALL only, PB measures from early time points correlated with relapse incidence (CIR). Best separation occurred at threshold <1 blast/μL at day 8 (5-year CIR 0.02 ± 0.02 vs 0.12 ± 0.03; P = 0.044). Patients with highest relapse risk were not distinguishable, but PB-MRD at days 33 and 52 correlated with prednisone response and postinduction BM-MRD by PCR (P < 0.001). Kinetic assessment did not convey any advantage. In multivariate analysis including day 15 BM-MRD, PB-MRD measures lost statistical power.

CONCLUSIONS

In summary, PB-MRD in pediatric B-ALL correlates with outcome and risk parameters, but its prognostic significance is not strong enough to substitute for BM assessment in AIEOP-BFM trials. It might, however, be valuable in treatment environments not using multifaceted risk stratification with other MRD measures.

T-Cell Receptor Rearrangements Determined Using Fragment Analysis in Patients With T-Acute Lymphoblastic Leukemia

Background

Chromosomal abnormalities and common genetic rearrangements related to T-acute lymphoblastic leukemia (T-ALL) are not clear. We investigated T-cell receptor (TCR) rearrangement in Korean T-ALL patients by fragment analysis, examining frequency, association between clinicopathologic characteristics and TCR clonality, and feasibility for detecting minimal residual disease (MRD).

Methods

In 51 Korean patients diagnosed as having T-ALL, TCR rearrangement was analyzed using the IdentiClone TCR gene clonality assay (InVivoScribe Technologies, San Diego, CA, USA) from archived bone marrow specimens. Limit of detection (LOD) and clonal stability at relapse were evaluated. The association between clinical prognosis and TCR clonality was examind by age and immunophenotypic classification.

Results

Thirty-eight patients (74.5%) had 62 clonal products of TCRβ, TCRγ, and/or TCRδ rearrangements at diagnosis. Children with T-ALL (<12 years) showed a higher frequency of clonality (93.8%) than adolescents/adults (65.7%; ≥12 years). Patients with a mature immunophenotype (84.4%) showed a relatively higher frequency of clonality than those with the immature immunophenotype (57.9%). Survival and event-free survival were not influenced by immunophenotype or TCR clonality. The LOD was 1%. Clonal evolution at the relapse period was noted.

Conclusions

The overall detection rate of TCR clonality was 74.5%. Survival did not differ by TCR clonality or immunophenotype and age group. Fragment analysis of TCR rearrangement cannot be used to assess MRD due to low sensitivity. Further research on the relationship between prognosis and frequency of TCR rearrangements is needed, using more sensitive methods to detect clonality and monitor MRD.

Methods and role of minimal residual disease after stem cell transplantation

Relapse is the major cause of treatment failure after stem cell transplantation. Despite the fact that relapses occurred even if transplantation was performed in complete remission, it is obvious that minimal residual disease is present though not morphologically evident. Since adaptive immunotherapy by donor lymphocyte infusion or other novel cell therapies as well as less toxic drugs, which can be used after transplantation, the detection of minimal residual disease (MRD) has become a clinical important variable for outcome. Besides the increasing options to treat MRD, the most advanced technologies currently allow to detect residual malignant cells with a sensitivity of 10^-5 to 10^-6.Under the patronage of the European Society for Blood and Marrow Transplantation (EBMT) and the American Society for Blood and Marrow Transplantation (ASBMT) the 3rd workshop was held on 4/5 November 2016 in Hamburg/Germany, with the aim to present an up-to-date status of epidemiology and biology of relapse and to summarize the currently available options to prevent and treat post-transplant relapse. Here the current methods and role of minimal residual disease for myeloid and lymphoid malignancies are summarized.

Genome-wide association study identifies susceptibility loci for B-cell childhood acute lymphoblastic leukemia

Genome-wide association studies (GWAS) have advanced our understanding of susceptibility to B-cell precursor acute lymphoblastic leukemia (BCP-ALL); however, much of the heritable risk remains unidentified. Here, we perform a GWAS and conduct a meta-analysis with two existing GWAS, totaling 2442 cases and 14,609 controls. We identify risk loci for BCP-ALL at 8q24.21 (rs28665337, P = 3.86 × 10-9, odds ratio (OR) = 1.34) and for ETV6-RUNX1 fusion-positive BCP-ALL at 2q22.3 (rs17481869, P = 3.20 × 10-8, OR = 2.14). Our findings provide further insights into genetic susceptibility to ALL and its biology.

A study on the predictability of acute lymphoblastic leukaemia response to treatment using a hybrid oncosimulator

Efficient use of Virtual Physiological Human (VPH)-type models for personalized treatment response prediction purposes requires a precise model parameterization. In the case where the available personalized data are not sufficient to fully determine the parameter values, an appropriate prediction task may be followed. This study, a hybrid combination of computational optimization and machine learning methods with an already developed mechanistic model called the acute lymphoblastic leukaemia (ALL) Oncosimulator which simulates ALL progression and treatment response is presented. These methods are used in order for the parameters of the model to be estimated for retrospective cases and to be predicted for prospective ones. The parameter value prediction is based on a regression model trained on retrospective cases. The proposed Hybrid ALL Oncosimulator system has been evaluated when predicting the pre-phase treatment outcome in ALL. This has been correctly achieved for a significant percentage of patient cases tested (approx. 70% of patients). Moreover, the system is capable of denying the classification of cases for which the results are not trustworthy enough. In that case, potentially misleading predictions for a number of patients are avoided, while the classification accuracy for the remaining patient cases further increases. The results obtained are particularly encouraging regarding the soundness of the proposed methodologies and their relevance to the process of achieving clinical applicability of the proposed Hybrid ALL Oncosimulator system and VPH models in general.

Influence of IL15 gene variations on the clinical features, treatment response and risk of developing childhood acute lymphoblastic leukemia in Latvian population

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Modern treatment protocols allow achievement of long-term event-free survival rates in up to 85% of cases, although the treatment response varies among different patient groups. It is hypothesized that treatment response is influenced by the IL15 gene variations, although research results are conflicting. To analyze IL15 gene variations influence treatment response, clinical course and the risk of developing ALL we performed a case-control and family-based study. The study included 81 patients with childhood ALL. DNA samples of both or one biological parent were available for 62 of ALL patients and 130 age and gender adjusted healthy samples were used as a control group. Analyzed IL15 gene variations: rs10519612, rs10519613 and rs17007695 were genotyped using PCR-RFLP assay. Our results shows that IL15 gene variations haplotypes are associated with the risk of developing childhood ALL (p < 0.05), although there is no such association for the variations separately. The variations rs10519612 and rs1059613 in a recessive pattern of inheritance were associated with hyperdiploidy (p = 0.048). Analyzed genetic variations had no impact on other clinical features and treatment response (assessed by the minimal residual disease) in our study.

Absolute lymphocyte counts at end of induction correlate with distinct immune cell compartments in pediatric B cell precursor acute lymphoblastic leukemia

Several retrospective studies in children with B cell precursor (BCP) acute lymphoblastic leukemia (ALL) provided clinical evidence that higher absolute lymphocyte counts (ALC) early into treatment significantly correlated with improved relapse-free and overall survival. It still remains unknown, however, whether the predictive role of higher ALCs reflects general bone marrow recovery or a more specific attribute of immune function. To investigate this question, we implemented a prospective observational cohort study in 20 children with BCP ALL on day 29 (D29) of induction chemotherapy and immunophenotyped their lymphoid (T, B and natural killer cells) and myeloid (neutrophils, monocytes, dendritic cells) compartments. In a first evaluation of a cohort treated with Children's Oncology Group-based induction chemotherapy, the immune cell compartments were differentially depleted at D29. Neither gender, risk status, minimal residual disease, nor bone marrow recovery markers correlated with D29 ALC. In contrast, both CD3+ T cell and dendritic cell compartments, which did not correlate with age, significantly correlated with D29 ALC (p < 0.0001). In addition, subset complexity of cellular immune compartments was preserved at D29. This study reveals that D29 ALC significantly correlates with distinct immune cell compartments but not with bone marrow recovery markers, suggesting that higher D29 ALCs may contribute to leukemia control by inducing specific host immune activity.

Minimal residual disease (MRD) detection using rearrangement of immunoglobulin/T cell receptor genes in adult patients with acute lymphoblastic leukemia (ALL)

MRD detection with allele-specific oligonucleotide-quantitative polymerase chain reaction (ASO-qPCR) and using clone-specific immunoglobulin/T cell receptor rearrangements is considered as a powerful prognostic factor in acute lymphoblastic leukemia (ALL). In the present study, we evaluated an ASO-qPCR assay for MRD quantification in peripheral blood (PB) samples of adult patients with ALL. DNA was isolated from PB samples of patients with newly diagnosed ALL. They were first investigated by multiplex-PCR assay to identify V/J usage. An ASO-qPCR technique was then applied for 2.5-year monthly MRD quantification for detection of patient-specific Ig/TCR receptor rearrangements as a molecular target. From 98 patients who were diagnosed as ALL, 72 (73.5%) were enrolled in the present study for MRD detection. MRD was successfully quantified in patients with 1-month interval time. MRD level at the end of induction therapy up to day 88 was the only significant prognostic factor. Regarding MRD level, patients were categorized into two groups of low and high-risk. 2.5-year OS in all three time points (days 28, 58 and 88) were significantly lower in high-risk group (P < 0.008). The results of the 2.5-year MRD detection indicate that MRD level at the end of induction up to about 6 months after the first diagnosis was associated with clinical outcome. This study may highlight the usefulness of PB and the definitions of cut-off level for early prediction of relapse and for stratifying ALL patients. Short-interval time points and frequent PB sampling to monitor MRD level is suggested for early clinical relapse prediction and clinical management of the disease.

Reduced-Intensity Delayed Intensification in Standard-Risk Pediatric Acute Lymphoblastic Leukemia Defined by Undetectable Minimal Residual Disease: Results of an International Randomized Trial (AIEOP-BFM ALL 2000)

Purpose Delayed intensification (DI) is an integral part of treatment of childhood acute lymphoblastic leukemia (ALL), but it is associated with relevant toxicity. Therefore, standard-risk patients of trial AIEOP-BFM ALL 2000 (Combination Chemotherapy Based on Risk of Relapse in Treating Young Patients With ALL) were investigated with the specific aim to reduce treatment intensity. Patients and Methods Between July 2000 and July 2006, 1,164 patients (1 to 17 years of age) with standard-risk ALL (defined as the absence of high-risk cytogenetics and undetectable minimal residual disease on days 33 and 78) were randomly assigned to either experimental reduced-intensity DI (protocol III; P-III) or standard DI (protocol II; P-II). Cumulative drug doses of P-III were reduced by 30% for dexamethasone and 50% for vincristine, doxorubicin, and cyclophosphamide, which shortened the treatment duration from 49 to 29 days. The study aimed at noninferiority of reduced-intensity P-III; analyses were performed according to treatment given. Results For P-III and P-II, respectively, the 8-year rate of disease-free survival (± SE) was 89.2 ± 1.3% and 92.3 ± 1.2% ( P = .04); cumulative incidence of relapse, 8.7 ± 1.2% and 6.4 ± 1.1% ( P = .09); and overall survival, 96.1 ± 0.8% and 98.0 ± 0.6% ( P = .06). Patients with ETV6-RUNX1-positive ALL and patients 1 to 6 years of age performed equally well in both arms. The incidence of death during remission was comparable, which indicates equivalent toxicity. The 8-year cumulative incidence rate of secondary malignancies was 1.3 ± 0.5% and 0.6 ± 0.4% for P-III and P-II, respectively ( P = .37). Conclusion Although the criteria used for the standard-risk definition in this trial identified patients with exceptionally good prognosis, reduction of chemotherapy was not successful mainly because of an increased rate of relapse. The data suggest that treatment reduction is feasible in specific subgroups, which underlines the biologic heterogeneity of this cohort selected according to treatment response.

Predictive value of minimal residual disease in Philadelphia-chromosome-positive acute lymphoblastic leukemia treated with imatinib in the European intergroup study of post-induction treatment of Philadelphia-chromosome-positive acute lymphoblastic leukemia, based on immunoglobulin/T-cell receptor and BCR/ABL1 methodologies

The prognostic value of minimal residual disease (MRD) in Philadelphia-chromosome-positive (Ph+) childhood acute lymphoblastic leukemia (ALL) treated with tyrosine kinase inhibitors is not fully established. We detected MRD by real-time quantitative polymerase chain reaction (RQ-PCR) of rearranged immunoglobulin/T-cell receptor genes (IG/TR) and/or BCR/ABL1 fusion transcript to investigate its predictive value in patients receiving Berlin-Frankfurt-Münster (BFM) high-risk (HR) therapy and post-induction intermittent imatinib (the European intergroup study of post-induction treatment of Philadelphia-chromosome-positive acute lymphoblastic leukemia (EsPhALL) study). MRD was monitored after induction (time point (TP)1), consolidation Phase IB (TP2), HR Blocks, reinductions, and at the end of therapy. MRD negativity progressively increased over time, both by IG/TR and BCR/ABL1. Of 90 patients with IG/TR MRD at TP1, nine were negative and none relapsed, while 11 with MRD<5×10⁻⁴ and 70 with MRD≥5×10⁻⁴ had a comparable 5-year cumulative incidence of relapse of 36.4 (15.4) and 35.2 (5.9), respectively. Patients who achieved MRD negativity at TP2 had a low relapse risk (5-yr cumulative incidence of relapse (CIR)=14.3[9.8]), whereas those who attained MRD negativity at a later date showed higher CIR, comparable to patients with positive MRD at any level. BCR/ABL1 MRD negative patients at TP1 had a relapse risk similar to those who were IG/TR MRD negative (1/8 relapses). The overall concordance between the two methods is 69%, with significantly higher positivity by BCR/ABL1. In conclusion, MRD monitoring by both methods may be functional not only for measuring response but also for guiding biological studies aimed at investigating causes for discrepancies, although from our data IG/TR MRD monitoring appears to be more reliable. Early MRD negativity is highly predictive of favorable outcome. The earlier MRD negativity is achieved, the better the prognosis.

Oncogenetic mutations combined with MRD improve outcome prediction in pediatric T-cell acute lymphoblastic leukemia

Risk stratification in childhood T-cell acute lymphoblastic leukemia (T-ALL) is mainly based on minimal residual disease (MRD) quantification. Whether oncogenetic mutation profiles can improve the discrimination of MRD-defined risk categories was unknown. Two hundred and twenty FRALLE2000T-treated patients were tested retrospectively for NOTCH1/FBXW7/RAS and PTEN alterations. Patients with NOTCH1/FBXW7 (N/F) mutations and RAS/PTEN (R/P) germ line (GL) were classified as oncogenetic low risk (gLoR; n = 111), whereas those with N/F GL and R/P GL mutations or N/F and R/P mutations were classified as high risk (gHiR; n = 109). Day 35 MRD status was available for 191 patients. Five-year cumulative incidence of relapse (CIR) and disease-free survival were 36% and 60% for gHiR patients and 11% and 89% for gLoR patients, respectively. Importantly, among the 60% of patients with MRD <10^-4, 5-year CIR was 29% for gHiR patients and 4% for gLoR patients. Based on multivariable Cox models and stepwise selection, the 3 most discriminating variables were the oncogenetic classifier, MRD, and white blood cell (WBC) count. Patients harboring a WBC count ≥200 × 10⁹/L, gHiR classifier, and MRD ≥10^-4 demonstrated a 5-year CIR of 46%, whereas the 58 patients (30%) with a WBC count <200 × 10⁹/L, gLoR classifier, and MRD <10^-4 had a very low risk of relapse, with a 5-year CIR of only 2%. In childhood T-ALL, the N/F/R/P mutation profile is an independent predictor of relapse. When combined with MRD and a WBC count ≥200 × 10⁹/L, it identifies a significant subgroup of patients with a low risk of relapse.

EgoNet identifies differential ego-modules and pathways related to prednisolone resistance in childhood acute lymphoblastic leukemia

PURPOSE

To extract feature ego-modules and pathways in childhood acute lymphoblastic leukemia (ALL) resistant to prednisolone treatment, and further to explore the mechanisms behind prednisolone resistance.

MATERIALS AND METHODS

EgoNet algorithm was used to identify candidate ego-network modules, mainly via constructing differential co-expression network (DCN); selecting ego genes; collecting ego-network modules; refining candidate modules. Afterwards, statistical significance was calculated for these candidate modules. Biological functions of differential ego-network modules were identified using Reactome database. To verify this proposed method can lead to truly positive findings in clinical settings, support vector machine (SVM) was utilized to compute the AUC values for each significant pathway using 3-fold cross-validation method. To predict the reliability of our findings, another established method (attract) was used to identify the differential attractor modules using the same microarray profile.

RESULTS

After eliminating the modules with classification accuracy < 0.9 and node number < 15, only ego-network module 30 was eligible. After significance calculation, module 30 was significant. Module 30 was enriched in APC/C-mediated degradation of cell cycle proteins. The AUC for the significant pathway of APC/C-mediated degradation of cell cycle proteins was 0.915. Although the attract method obtained more modules, the module identified by our proposed method owned more gene nodes, and had more classification ability (AUC = 0.915).

CONCLUSION

One differential ego-network module identified in childhood ALL resistance to prednisolone based on DCN and EgoNet, might be helpful to reveal the mechanisms underlying prednisolone resistance in childhood ALL.

Molecular characterization of acute lymphoblastic leukemia with high CRLF2 gene expression in childhood

BACKGROUND

A high-level expression of the CRLF2 gene is frequent in precursor B-cell acute lymphoblastic leukemia (pB-ALL) and can be caused by different genetic aberrations. The presence of the most frequent alteration, the P2RY8/CRLF2 fusion, was shown to be associated with a high relapse incidence in children treated according to ALL-Berlin-Frankfurt-Münster (BFM) protocols, which is poorly understood. Moreover, the frequency of other alterations has not been systematically analyzed yet.

PROCEDURE

CRLF2 mRNA expression and potential genetic aberrations causing a CRLF2 high expression were prospectively assessed in 1,105 patients treated according to the Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP)-BFM ALL 2009 protocol. Additionally, we determined copy number alterations in selected B-cell differentiation genes for all CRLF2 high-expressing pB-ALL cases, as well as JAK2 and CRLF2 mutations.

RESULTS

A CRLF2 high expression was detected in 26/178 (15%) T-cell acute lymphoblastic leukemia (T-ALL) cases, 21 of them (81%) had been stratified as high-risk patients by treatment response. In pB-ALL, a CRLF2 high expression was determined in 91/927 (10%) cases; the P2RY8/CRLF2 rearrangement in 44/91 (48%) of them, supernumerary copies of CRLF2 in 18/91 (20%), and, notably, the IGH/CRLF2 translocation was detected in 16/91 (18%). Remarkably, 7 of 16 (44%) patients with IGH/CRLF2 translocation had already relapsed. P2RY8/CRLF2- and IGH/CRLF2-positive samples (70 and 94%, respectively) were characterized by a high frequency of additional deletions in B-cell differentiation genes such as IKZF1 or PAX5.

CONCLUSION

Our data suggest that this high frequency of genetic aberrations in the context of a high CRLF2 expression could contribute to the high risk of relapse in P2RY8/CRLF2- and IGH/CRLF2-positive ALL.

Association of Minimal Residual Disease With Clinical Outcome in Pediatric and Adult Acute Lymphoblastic Leukemia: A Meta-analysis

Importance

Minimal residual disease (MRD) refers to the presence of disease in cases deemed to be in complete remission by conventional pathologic analysis. Assessing the association of MRD status following induction therapy in patients with acute lymphoblastic leukemia (ALL) with relapse and mortality may improve the efficiency of clinical trials and accelerate drug development.

Objective

To quantify the relationships between event-free survival (EFS) and overall survival (OS) with MRD status in pediatric and adult ALL using publications of clinical trials and other databases.

Data Sources

Clinical studies in ALL identified via searches of PubMed, MEDLINE, and clinicaltrials.gov.

Study Selection

Our search and study screening process adhered to the PRISMA Guidelines. Studies that addressed EFS or OS by MRD status in patients with ALL were included; reviews, abstracts, and studies with fewer than 30 patients or insufficient MRD description were excluded.

Data Extraction and Synthesis

Study sample size, patient age, follow-up time, timing of MRD assessment (postinduction or consolidation), MRD detection method, phenotype/genotype (B cell, T cell, Philadelphia chromosome), and EFS and OS. Searches of PubMed and MEDLINE identified 566 articles. A parallel search on clinicaltrials.gov found 67 closed trials and 62 open trials as of 2014. Merging results of 2 independent searches and applying exclusions gave 39 publications in 3 arms of patient populations (adult, pediatric, and mixed). We performed separate meta-analyses for each of these 3 subpopulations.

Results

The 39 publications comprised 13 637 patients: 16 adult studies (2076 patients), 20 pediatric (11 249 patients), and 3 mixed (312 patients). The EFS hazard ratio (HR) for achieving MRD negativity is 0.23 (95% Bayesian credible interval [BCI] 0.18-0.28) for pediatric patients and 0.28 (95% BCI, 0.24-0.33) for adults. The respective HRs in OS are 0.28 (95% BCI, 0.19-0.41) and 0.28 (95% BCI, 0.20-0.39). The effect was similar across all subgroups and covariates.

Conclusions and Relevance

The value of having achieved MRD negativity is substantial in both pediatric and adult patients with ALL. These results are consistent across therapies, methods of and times of MRD assessment, cutoff levels, and disease subtypes. Minimal residual disease status warrants consideration as an early measure of disease response for evaluating new therapies, improving the efficiency of clinical trials, accelerating drug development, and for regulatory approval. A caveat is that an accelerated approval of a particular new drug using an intermediate end point, such as MRD, would require confirmation using traditional efficacy end points.

An Fc-engineered CD19 antibody eradicates MRD in patient-derived MLL-rearranged acute lymphoblastic leukemia xenografts

Antibody therapy constitutes a major advance in the treatment of B-cell precursor acute lymphoblastic leukemia (BCP-ALL). To evaluate the efficacy and the mechanisms of action of CD19 monoclonal antibody therapy in pediatric BCP-ALL, we tested an Fc-engineered CD19 antibody carrying the S239D/I332E mutation for improved effector cell recruitment (CD19-DE). Patient-derived xenografts (PDX) of pediatric mixed-lineage leukemia gene (MLL)-rearranged ALL were established in NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) mice. Antibody CD19-DE was efficient in prolonging the survival of NSG mice in a minimal residual disease (MRD) model. The majority of surviving mice remained polymerase chain reaction (PCR)-MRD negative after treatment. When antibody therapy was initiated in overt leukemia, antibody CD19-DE was still efficient in prolonging survival of xenografted mice in comparison with nontreated control animals, but the effects were less pronounced than in the MRD setting. Importantly, the combination of antibody CD19-DE and cytoreduction by chemotherapy (dexamethasone, vincristine, PEG-asparaginase) resulted in significantly improved survival rates in xenografted mice. Antibody CD19-DE treatment was also efficient in a randomized phase 2-like PDX trial using 13 MLL-rearranged BCP-ALL samples. Macrophage depletion by liposomal clodronate resulted in a reversal of the beneficial effects of CD19-DE, suggesting an important role for macrophages as effector cells. In support of this finding, CD19-DE was found to enhance phagocytosis of patient-derived ALL blasts by human macrophages in vitro. Thus, Fc-engineered CD19 antibodies may represent a promising treatment option for infants and children with MLL-rearranged BCP-ALL who have a poor outcome when treated with chemotherapy only.

TP53 in adult acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is characterized by a great biological and clinical heterogeneity. Despite most adult patients enter complete hematologic remission after induction therapy only 40% survive five or more years. Over the last 20 years, the definition of an accurate biologic leukemia profile and the minimal residual disease evaluation in addition to conventional risk criteria led to a significant improvement for the risk stratification. The alterations of the oncosuppressor gene TP53, including deletions, sequence mutations and defect in its expression due to regulatory defects, define a new important predictor of adverse outcome. More recently, new drugs have been developed with the aim of targeting p53 protein itself or its regulatory molecules, such as Mdm2, and restoring the pathway functionality. Therefore, TP53 alterations should be considered in the diagnostic work-up to identify high risk ALL patients in need of intensive treatment strategies or eligible for new innovative targeted therapies.

Central nervous system involvement in acute lymphoblastic leukemia is mediated by vascular endothelial growth factor

In acute lymphoblastic leukemia (ALL), central nervous system (CNS) involvement is a major clinical concern. Despite nondetectable CNS leukemia in many cases, prophylactic CNS-directed conventional intrathecal chemotherapy is required for relapse-free survival, indicating subclinical CNS manifestation in most patients. However, CNS-directed therapy is associated with long-term sequelae, including neurocognitive deficits and secondary neoplasms. Therefore, molecular mechanisms and pathways mediating leukemia-cell entry into the CNS need to be understood to identify targets for prophylactic and therapeutic interventions and develop alternative CNS-directed treatment strategies. In this study, we analyzed leukemia-cell entry into the CNS using a primograft ALL mouse model. We found that primary ALL cells transplanted onto nonobese diabetic/severe combined immunodeficiency mice faithfully recapitulated clinical and pathological features of meningeal infiltration seen in patients with ALL. ALL cells that had entered the CNS and were infiltrating the meninges were characterized by high expression of vascular endothelial growth factor A (VEGF). Although cellular viability, growth, proliferation, and survival of ALL cells were found to be independent of VEGF, transendothelial migration through CNS microvascular endothelial cells was regulated by VEGF. The importance of VEGF produced by ALL cells in mediating leukemia-cell entry into the CNS and leptomeningeal infiltration was further demonstrated by specific reduction of CNS leukemia on in vivo VEGF capture by the anti-VEGF antibody bevacizumab. Thus, we identified a mechanism of ALL-cell entry into the CNS, which by targeting VEGF signaling may serve as a novel strategy to control CNS leukemia in patients, replacing conventional CNS-toxic treatment.

Ordinary differential equations and Boolean networks in application to modelling of 6-mercaptopurine metabolism

We consider two approaches to modelling the cell metabolism of 6-mercaptopurine, one of the important chemotherapy drugs used for treating acute lymphocytic leukaemia: kinetic ordinary differential equations, and Boolean networks supplied with one controlling node, which takes continual values. We analyse their interplay with respect to taking into account ATP concentration as a key parameter of switching between different pathways. It is shown that the Boolean networks, which allow avoiding the complexity of general kinetic modelling, preserve the possibility of reproducing the principal switching mechanism.

Flow cytometric detection of minimal residual disease in B-lineage acute lymphoblastic leukemia by using "MRD lite" panel

BACKGROUND

Normal B lymphoid precursors that express CD19, CD10, and/or CD34 are highly sensitive to corticosteroids and after two weeks of remission-induction therapy, they form less than 0.01% of the bone marrow population. More than 0.01% of such cells indicate minimal residual disease (MRD). MRD "lite" panel uses only three antibodies, namely CD19, CD10, and CD34 for MRD detection in cases of B-lineage acute lymphoblastic leukemia (B-ALL) expressing CD19, CD10, and/or CD34 by flow cytometry.

METHODS

Fifteen cases of B-ALL were studied for MRD at Day 19 of remission-induction therapy by employing a simplified MRD detection protocol using a 3-color fluorochrome conjugated antibody panel (CD19, CD10, and CD34) on bone marrow aspirate samples.

RESULTS

All cases at diagnosis expressed CD19, CD10, and CD34. Of fifteen patients, five (33.33%) were MRD negative with less than 0.01% of mononuclear cells and remaining ten cases (66.66%) were MRD positive, with the level of 0.01% to less than 0.1% cells.

CONCLUSION

The MRD assay used in this study is a simplified method for detecting MRD at Day 19 of remission-induction therapy for B-lineage ALL. This MRD assay is an effective and useful methodology in cases of B-ALL expressing CD19, CD10, and/or CD34 by flow cytometry.

Bioluminescence Imaging Enhances Analysis of Drug Responses in a Patient-Derived Xenograft Model of Pediatric ALL

Purpose: Robust preclinical models of pediatric acute lymphoblastic leukemia (ALL) are essential in prioritizing promising therapies for clinical assessment in high-risk patients. Patient-derived xenograft (PDX) models of ALL provide a clinically relevant platform for assessing novel drugs, with efficacy generally assessed by enumerating circulating human lymphoblasts in mouse peripheral blood (PB) as an indicator of disease burden. While allowing indirect measurement of disease burden in real time, this technique cannot assess treatment effects on internal reservoirs of disease. We explore benefits of bioluminescence imaging (BLI) to evaluate drug responses in ALL PDXs, compared with PB monitoring. BLI-based thresholds of drug response are also explored.Experimental Design: ALL PDXs were lentivirally transduced to stably express luciferase and green fluorescent protein. In vivo PDX responses to an induction-type regimen of vincristine, dexamethasone, and L-asparaginase were assessed by BLI and PB. Residual disease at day 28 after treatment initiation was assessed by flow cytometric analysis of major organs. BLI and PB were subsequently used to evaluate efficacy of the Bcl-2 inhibitor venetoclax.Results: BLI considerably accelerated and enhanced detection of leukemia burden compared with PB and identified sites of residual disease during treatment in a quantitative manner, highlighting limitations in current PB-based scoring criteria. Using BLI alongside enumeration of human lymphoblasts in PB and bone marrow, we were able to redefine response criteria analogous to the clinical setting.Conclusions: BLI substantially improves the stringency of preclinical drug testing in pediatric ALL PDXs, which will likely be important in prioritizing effective agents for clinical assessment. Clin Cancer Res; 23(14); 3744-55. ©2017 AACR.

Standardized flow cytometry for highly sensitive MRD measurements in B-cell acute lymphoblastic leukemia

A fully-standardized EuroFlow 8-color antibody panel and laboratory procedure was stepwise designed to measure minimal residual disease (MRD) in B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) patients with a sensitivity of ≤10^-5, comparable to real-time quantitative polymerase chain reaction (RQ-PCR)-based MRD detection via antigen-receptor rearrangements. Leukocyte markers and the corresponding antibodies and fluorochromes were selected based on their contribution in separating BCP-ALL cells from normal/regenerating BCP cells in multidimensional principal component analyses. After 5 multicenter design-test-evaluate-redesign phases with a total of 319 BCP-ALL patients at diagnosis, two 8-color antibody tubes were selected, which allowed separation between normal and malignant BCP cells in 99% of studied patients. These 2 tubes were tested with a new erythrocyte bulk-lysis protocol allowing acquisition of high cell numbers in 377 bone marrow follow-up samples of 178 BCP-ALL patients. Comparison with RQ-PCR-based MRD data showed a clear positive relation between the percentage concordant cases and the number of cells acquired. For those samples with >4 million cells acquired, concordant results were obtained in 93% of samples. Most discordances were clarified upon high-throughput sequencing of antigen-receptor rearrangements and blind multicenter reanalysis of flow cytometric data, resulting in an unprecedented concordance of 98% (97% for samples with MRD < 0.01%). In conclusion, the fully standardized EuroFlow BCP-ALL MRD strategy is applicable in >98% of patients with sensitivities at least similar to RQ-PCR (≤10^-5), if sufficient cells (>4 × 10⁶, preferably more) are evaluated.

Recent advances in the management of pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common malignancy in childhood. Despite enormous improvement of prognosis during the last half century, ALL remains a major cause of childhood cancer-related mortality. During the past decade, whole genomic methods have enhanced our knowledge of disease biology. Stratification of therapy according to early treatment response measured by minimal residual disease allows risk group assignment into different treatment arms, ranging from reduction to intensification of treatment. Progress has been achieved in academic clinical trials by optimization of combined chemotherapy, which continues to be the mainstay of contemporary treatment. The availability of suitable volunteer main histocompatibility antigen-matched unrelated donors has increased the rates of hematopoietic stem cell transplantation (HSCT) over the past two decades. Allogeneic HSCT has become an alternative treatment for selected, very-high-risk patients. However, intensive treatment burdens children with severe acute toxic effects that can cause permanent organ damage and even toxic death. Immunotherapeutic approaches have recently come to the forefront in ALL therapy. Monoclonal antibodies blinatumomab and inotuzumab ozogamicin as well as gene-modified T cells directed to specific target antigens have shown efficacy against resistant/relapsed leukemia in phase I/II studies. Integration of these newer modalities into combined regimens with chemotherapy may rescue a subset of children not curable by contemporary therapy. Another major challenge will be to incorporate less toxic regimens into the therapy of patients with low-risk disease who have a nearly 100% chance of being cured, and the ultimate goal is to improve their quality of life while maintaining a high cure rate.

Pre-Emptive Immunotherapy for Clearance of Molecular Disease in Childhood Acute Lymphoblastic Leukemia after Transplantation

Monitoring of minimal residual disease (MRD) or chimerism may help guide pre-emptive immunotherapy (IT) with a view to preventing relapse in childhood acute lymphoblastic leukemia (ALL) after transplantation. Patients with ALL who consecutively underwent transplantation in Frankfurt/Main, Germany between January 1, 2005 and July 1, 2014 were included in this retrospective study. Chimerism monitoring was performed in all, and MRD assessment was performed in 58 of 89 patients. IT was guided in 19 of 24 patients with mixed chimerism (MC) and MRD and by MRD only in another 4 patients with complete chimerism (CC). The 3-year probabilities of event-free survival (EFS) were .69 ± .06 for the cohort without IT and .69 ± .10 for IT patients. Incidences of relapse (CIR) and treatment-related mortality (CITRM) were equally distributed between both cohorts (without IT: 3-year CIR, .21 ± .05, 3-year CITRM, .10 ± .04; IT patients: 3-year CIR, .18 ± .09, 3-year CITRM .13 ± .07). Accordingly, 3-year EFS and 3-year CIR were similar in CC and MC patients with IT, whereas MC patients without IT experienced relapse. IT was neither associated with an enhanced immune recovery nor an increased risk for acute graft-versus-host disease. Relapse prevention by IT in patients at risk may lead to the same favorable outcome as found in CC and MRD-negative-patients. This underlines the importance of excellent MRD and chimerism monitoring after transplantation as the basis for IT to improve survival in childhood ALL.

Minimal Residual Disease Detection and Evolved IGH Clones Analysis in Acute B Lymphoblastic Leukemia Using IGH Deep Sequencing

Acute B lymphoblastic leukemia (B-ALL) is one of the most common types of childhood cancer worldwide and chemotherapy is the main treatment approach. Despite good response rates to chemotherapy regiments, many patients eventually relapse and minimal residual disease (MRD) is the leading risk factor for relapse. The evolution of leukemic clones during disease development and treatment may have clinical significance. In this study, we performed immunoglobulin heavy chain (IGH) repertoire high throughput sequencing (HTS) on the diagnostic and post-treatment samples of 51 pediatric B-ALL patients. We identified leukemic IGH clones in 92.2% of the diagnostic samples and nearly half of the patients were polyclonal. About one-third of the leukemic clones have correct open reading frame in the complementarity determining region 3 (CDR3) of IGH, which demonstrates that the leukemic B cells were in the early developmental stage. We also demonstrated the higher sensitivity of HTS in MRD detection and investigated the clinical value of using peripheral blood in MRD detection and monitoring the clonal IGH evolution. In addition, we found leukemic clones were extensively undergoing continuous clonal IGH evolution by variable gene replacement. Dynamic frequency change and newly emerged evolved IGH clones were identified upon the pressure of chemotherapy. In summary, we confirmed the high sensitivity and universal applicability of HTS in MRD detection. We also reported the ubiquitous evolved IGH clones in B-ALL samples and their response to chemotherapy during treatment.

Development-associated immunophenotypes reveal the heterogeneous and individualized early responses of adult B-acute lymphoblastic leukemia

B cell acute lymphoblastic leukemia (B-ALL) exhibits phenotypes reminiscent of normal stages of B-cell development. As demonstrated by flow cytometry, the immunophenotypes are able to determine the stages of B cell development. Multicolor flow cytometry (MFC) is more accurate at identifying cell populations. In this study, 9-color panels, including CD10, CD19, CD20, CD22, CD34, CD79a, CD179a, and IgM, which are sequentially expressed during B cell development, were designed to detect the leukemia cell subpopulations in adult B-ALL patients. In 23 patients at diagnosis, 192 heterogeneous subpopulations of leukemia cells were detected. Compared with their counterparts at diagnosis and after the 1st course of induction therapy, the responses of the subpopulations were also heterogeneous. In the CD10 population, the residual B cell subpopulations in the BCR/ABL patients were obviously reduced compared to those in the BCR/ABL patients. New subpopulations were detected in 22 of 23 patients and were primarily located in the CD34CD10 populations. Subpopulations of clonal evolution were heterogeneous after induction therapy. Our results suggest that the subpopulations in B-ALL patients should be dynamically monitored by development-associated immunophenotyping before, during, and after induction therapy and to predict the prognosis of the disease.

Successful Therapy Reduction and Intensification for Childhood Acute Lymphoblastic Leukemia Based on Minimal Residual Disease Monitoring: Study ALL10 From the Dutch Childhood Oncology Group

PURPOSE

Outcome of childhood acute lymphoblastic leukemia (ALL) improved greatly by intensifying chemotherapy for all patients. Minimal residual disease (MRD) levels during the first months predict outcome and may select patients for therapy reduction or intensification.

METHODS

Patients 1 to 18 years old with ALL were stratified on the basis of MRD levels after the first and second course of chemotherapy. Thereafter, therapy was substantially reduced in patients with undetectable MRD (standard risk) and intensified in patients with intermediate (medium risk) and high (high risk) levels of MRD. Seven hundred seventy-eight consecutive patients were enrolled. The method of analysis was intention-to-treat. Outcome was compared with historical controls.

RESULTS

In MRD-based standard-risk patients, the 5-year event-free survival (EFS) rate was 93% (SE 2%), the 5-year survival rate was 99% (SE 1%), and the 5-year cumulative incidence of relapse rate was 6% (SE 2%). The safety upper limit of number of observation years was reached and therapy reduction was declared safe.MRD-based medium-risk patients had a significantly higher 5-year EFS rate (88%, SE 2%) with therapy intensification (including 30 weeks of asparaginase exposure and dexamethasone/vincristine pulses) compared with historical controls (76%, SE 6%). Intensive chemotherapy and stem cell transplantation in MRD-based high-risk patients resulted in a significantly better 5-year EFS rate (78%, SE 8% v 16%, SE 8% in controls). Overall outcome improved significantly (5-year EFS rate 87%, 5-year survival rate 92%, and 5-year cumulative incidence of relapse rate 8%) compared with preceding Dutch Childhood Oncology Group protocols.

CONCLUSION

Chemotherapy was substantially reduced safely in one-quarter of children with ALL who were selected on the basis of undetectable MRD levels, without jeopardizing the survival rate. Outcomes of patients with intermediate and high levels of MRD improved with therapy intensification.

Current Strategies for the Detection of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. Current treatment strategies for childhood ALL result in long-term remission for approximately 90% of patients. However, the therapeutic response is worse among those who relapse. Several risk stratification approaches based on clinical and biological aspects have been proposed to intensify treatment in patients with high risk of relapse and reduce toxicity on those with a greater probability of cure.

The detection of residual leukemic cells (minimal residual disease, MRD) is the most important prognostic factor to identify high-risk patients, allowing redefinition of chemotherapy. In the last decades, several standardized research protocols evaluated MRD using immunophenotyping by flow cytometry and/or real-time quantitative polymerase chain reaction at different time points during treatment. Both methods are highly sensitive (10⁻³ a 10⁻⁵), but expensive, complex, and, because of that, require qualified staff and frequently are restricted to reference centers.

The aim of this article was to review technical aspects of immunophenotyping by flow cytometry and real-time quantitative polymerase chain reaction to evaluate MRD in ALL.

Minimal residual disease detection using flow cytometry: Applications in acute leukemia

Minimal residual disease (MRD) describes disease that can be diagnosed by methodologies other than conventional morphology, and includes molecular methods (like polymerase chain reaction (PCR)) or flow cytometry (FCM). Detection and monitoring of MRD is becoming the standard of care, considering its importance in predicting the treatment outcome. MRD aids in identifying high-risk patients and hence therapy can be intensified in them while deintensification of therapy can prevent long-term sequelae of chemotherapy in low-risk category. FCM is considered as a less labor-intensive and faster MRD technique as compared to PCR although it has its own share of disadvantages. Current immune-based methodologies for detection of MRD depend on establishing leukemia-associated aberrant immunophenotype (LAIP), at diagnosis or relapse and use this information at specified time points for detection of MRD, or apply a standardized panel of antibody combinations for all MRD cases, in a different-from-normal approach. This review highlights MRD detection by FCM and its application in acute leukemia.

Angiopoietins in the bone marrow microenvironment of acute lymphoblastic leukemia

OBJECTIVE

Angiogenesis have implications in leukemia biology. Angiopoietin 1 (Ang 1) is an angiogenic cytokine which is essential in survival and proliferation of endothelial cells. Angiopoietin 2 (Ang 2) promotes dissociation of pericytes and increases vascular permeability and stromal derived factor 1 alpha (SDF 1α) which is a key player in stem cell traffic in the bone marrow (BM), has stimulating effects on angiogenesis as well. Here, we investigated the role of the leukemic BM microenvironment and specifically, the role of SDF 1α-CXCR4 and Ang 1/Ang 2-Tie 2 axes.

METHODS

Here, Ang 1, Ang 2, and SDF 1α levels were measured in the BM plasma and in supernatants of mesenchymal stem/stromal cells (MSCs) of patients with ALL and compared with those of healthy controls.

RESULTS

The results showed that at diagnosis, BM plasma levels of Ang 1 and SDF 1α were significantly low and Ang 2 was high when compared to control values. Remission induction was associated with an increase in Ang 1/Ang 2 ratio and SDF levels in BM plasma.

DISCUSSION

The results suggest that BM microenvironment and leukemic cell-stroma interaction influences the secretion of Ang 1, 2 and SDF 1α, thus, may affect both angiogenesis, homing and mobilization of leukemic blasts.

Minimal Residual Disease Monitoring in Adult ALL to Determine Therapy

Almost 90 % of children and 50 % of adults with acute lymphoblastic leukemia (ALL) are cured by modern treatment regimens, with significant variations due to several disease- and host-related characteristics. The attainment of an early remission and the avoidance of relapse and treatment-related mortality are the fundamental therapeutic steps. In remission patients, the assessment of the disease response to early intensive therapy through the detection and monitoring of minimal residual disease (MRD) can accurately refine the individual prognosis and is increasingly used to support a risk-oriented treatment strategy. In this way, only the patients with an unfavorable MRD response are preferably selected for allogeneic stem cell transplantation, irrespective of their clinical risk class. This choice spares transplant-related toxicities to MRD responsive cases. Further advancement is expected by integrating the MRD analysis with improved pediatric-type regimens and novel targeting agents for ALL subsets at higher risk of relapse.

Incidence and outcome of osteonecrosis in children and adolescents after intensive therapy for acute lymphoblastic leukemia (ALL)

Osteonecrosis (ON), a significant complication following treatment of acute lymphoblastic leukemia (ALL), has a profound impact on quality of life of ALL survivors. We studied incidence and outcome of ON in patients treated on or according to Australian and New Zealand Children's Haematology/ Oncology Group (ANZCHOG) study 8 at The Children's Hospital at Westmead. The study involved retrospective chart review of the patients. ON was defined by development of symptoms and confirmed by magnetic resonance imaging. From 2002-2011, 251 patients (143M, 108F, 59 Standard Risk (SR), 159 Medium Risk (MR) 5 High Risk (HR), and 28 Very high risk (VHR)) were treated according to study 8. Eighteen (7M, 11F, 2 SR, 12 MR, 4 VHR) patients developed ON (7.2%). Median age at diagnosis was 13.05 years(4.3-16.7). Incidence of ON in patients > 10 years at diagnosis was 29%. Six out of 18 patients developed ON after allogeneic stem cell transplantation. Median time from diagnosis to the development of ON following chemotherapy for ALL was 1.15 years (range 0.25-2.12). Most patients were treated with intravenous Zoledronic acid. At last follow-up, three patients had undergone arthroplasty, two patients were symptom free, and the remaining 13 patients reported persistent pain with activity. A majority of patients with ON of the hips had radiological progression. Overall, 7% of patients with ALL developed ON. Age >10 years was the most important risk factor. At last follow-up, 70% of patients had persistent symptoms. Although Zoledronic acid improved pain, most patients with ON of the hips had radiological progression.

Detection and role of minimal disseminated disease in children with lymphoblastic lymphoma: The AIEOP experience

BACKGROUND

The use of intensive chemotherapy regimens in children with lymphoblastic lymphoma (LBL) has significantly improved outcome, but the salvage rate for these patients is still poor. The aim of this study was to evaluate the prognostic value of minimal disseminated disease (MDD), studied by multiparametric flow cytometry (MFC), in pediatric patients with T- and B-lineage LBL.

PROCEDURE

We examined bone marrow (BM) and peripheral blood (PB) samples from a series of 65 children affected by T- (52) and B-lineage (13) LBL using an MFC method; 10 of them were also analyzed for clonality of T-cell receptor gene rearrangements.

RESULTS

MDD was detected in 49% (32/65) of BM samples, whereas only 21% (14/65) were positive at standard morphological evaluation. Findings from MFC analyses of paired BM and PB samples were highly concordant. We analyzed the prognostic significance of MDD results detected at diagnosis in morphologically negative patients, as almost all relapsed cases (10/11) did not have any morphological involvement of BM at diagnosis. Using an MDD cut-off level of 3% by FCM (75th percentile), 5-year event-free survival (EFS) was 60% (SE ± 22) for patients with MDD >3% LBL cells versus 83% (SE ± 6) for the remaining patients (P = 0.04). No statistically significant difference in EFS was observed between LBL patients considering all the other clinical characteristics.

CONCLUSIONS

Our data demonstrated that MDD studied at diagnosis by MFC could represent a useful prognostic tool in childhood LBL and further application for better stratification is warranted.

Genetic alterations in glucocorticoid signaling pathway components are associated with adverse prognosis in children with relapsed ETV6/RUNX1-positive acute lymphoblastic leukemia

The ETV6/RUNX1 gene fusion defines the largest genetic subgroup of childhood ALL with overall rapid treatment response. However, up to 15% of cases relapse. Because an impaired glucocorticoid pathway is implicated in disease recurrence we studied the impact of genetic alterations by SNP array analysis in 31 relapsed cases. In 58% of samples, we found deletions in various glucocorticoid signaling pathway-associated genes, but only NR3C1 and ETV6 deletions prevailed in minimal residual disease poor responding and subsequently relapsing cases (p<0.05). To prove the necessity of a functional glucocorticoid receptor, we reconstituted wild-type NR3C1 expression in mutant, glucocorticoid-resistant REH cells and studied the glucocorticoid response in vitro and in a xenograft mouse model. While these results prove that glucocorticoid receptor defects are crucial for glucocorticoid resistance in an experimental setting, they do not address the essential clinical situation where glucocorticoid resistance at relapse is rather part of a global drug resistance.

Proposal for the standardization of flow cytometry protocols to detect minimal residual disease in acute lymphoblastic leukemia

Minimal residual disease is the most powerful predictor of outcome in acute leukemia and is useful in therapeutic stratification for acute lymphoblastic leukemia protocols. Nowadays, the most reliable methods for studying minimal residual disease in acute lymphoblastic leukemia are multiparametric flow cytometry and polymerase chain reaction. Both provide similar results at a minimal residual disease level of 0.01% of normal cells, that is, detection of one leukemic cell in up to 10,000 normal nucleated cells. Currently, therapeutic protocols establish the minimal residual disease threshold value at the most informative time points according to the appropriate methodology employed. The expertise of the laboratory in a cancer center or a cooperative group could be the most important factor in determining which method should be used. In Brazil, multiparametric flow cytometry laboratories are available in most leukemia treatment centers, but multiparametric flow cytometry processes must be standardized for minimal residual disease investigations in order to offer reliable and reproducible results that ensure quality in the clinical application of the method. The Minimal Residual Disease Working Group of the Brazilian Society of Bone Marrow Transplantation (SBTMO) was created with that aim. This paper presents recommendations for the detection of minimal residual disease in acute lymphoblastic leukemia based on the literature and expertise of the laboratories who participated in this consensus, including pre-analytical and analytical methods. This paper also recommends that both multiparametric flow cytometry and polymerase chain reaction are complementary methods, and so more laboratories with expertise in immunoglobulin/T cell receptor (Ig/TCR) gene assays are necessary in Brazil.

Comparison between qualitative and real-time polymerase chain reaction to evaluate minimal residual disease in children with acute lymphoblastic leukemia

INTRODUCTION

Minimal residual disease is an important independent prognostic factor that can identify poor responders among patients with acute lymphoblastic leukemia.

OBJECTIVE

The aim of this study was to analyze minimal residual disease using immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements by conventional polymerase chain reaction followed by homo-heteroduplex analysis and to compare this with real-time polymerase chain reaction at the end of the induction period in children with acute lymphoblastic leukemia.

METHODS

Seventy-four patients diagnosed with acute lymphoblastic leukemia were enrolled. Minimal residual disease was evaluated by qualitative polymerase chain reaction in 57 and by both tests in 44. The Kaplan-Meier and multivariate Cox methods and the log-rank test were used for statistical analysis.

RESULTS

Nine patients (15.8%) were positive for minimal residual disease by qualitative polymerase chain reaction and 11 (25%) by real-time polymerase chain reaction considering a cut-off point of 1×10(-3) for precursor B-cell acute lymphoblastic leukemia and 1×10(-2) for T-cell acute lymphoblastic leukemia. Using the qualitative method, the 3.5-year leukemia-free survival was significantly higher in children negative for minimal residual disease compared to those with positive results (84.1%±5.6% versus 41.7%±17.3%, respectively; p-value=0.004). There was no significant association between leukemia-free survival and minimal residual disease by real-time polymerase chain reaction. Minimal residual disease by qualitative polymerase chain reaction was the only variable significantly correlated to leukemia-free survival.

CONCLUSION

Given the difficulties in the implementation of minimal residual disease monitoring by real-time polymerase chain reaction in most treatment centers in Brazil, the qualitative polymerase chain reaction strategy may be a cost-effective alternative.

Secondary histiocytic sarcoma may cause apparent persistence or recurrence of minimal residual disease in childhood acute lymphoblastic leukemia

Histiocytic sarcoma (HS) is a rare disease with poor prognosis which may develop subsequent to acute lymphoblastic leukemia (ALL). Here we report two children treated within the AIEOP-BFM ALL 2009 trial: one patient succumbed to fulminant hemophagocytic lymphohistiocytosis triggered by HS during ALL maintenance therapy, the other patient had a smoldering course of HS for over 2 years, and subsequently died after allogeneic stem cell transplantation. In both cases, HS and ALL were clonally related and apparent return of minimal residual disease (MRD) was detected by qPCR in bone marrow. Thus, HS should be considered in ALL when MRD appears to persist or reappear.

Minimal residual disease analysis by eight-color flow cytometry in relapsed childhood acute lymphoblastic leukemia

Multiparametric flow cytometry is an alternative approach to the polymerase chain reaction method for evaluating minimal residual disease in treatment protocols for primary acute lymphoblastic leukemia. Given considerable differences between primary and relapsed acute lymphoblastic leukemia treatment regimens, flow cytometric assessment of minimal residual disease in relapsed leukemia requires an independent comprehensive investigation. In the present study we addressed evaluation of minimal residual disease by flow cytometry in the clinical trial for childhood relapsed acute lymphoblastic leukemia using eight-color flow cytometry. The major challenge of the study was to reliably identify low amounts of residual leukemic cells against the complex background of regeneration, characteristic of follow-up samples during relapse treatment. In a prospective study of 263 follow-up bone marrow samples from 122 patients with B-cell precursor acute lymphoblastic leukemia, we tested various B-cell markers, adapted the antibody panel to the treatment protocol, and evaluated its performance by a blinded parallel comparison with the polymerase chain reaction data. The resulting eight-color single-tube panel showed a consistently high overall concordance (P<0.001) and, under optimal conditions, sensitivity similar to that of the reference polymerase chain reaction method. Overall, evaluation of minimal residual disease by flow cytometry can be successfully integrated into the clinical management of relapsed childhood acute lymphoblastic leukemia either as complementary to the polymerase chain reaction or as an independent risk stratification tool. ALL-REZ BFM 2002 clinical trial information: NCT00114348.

Minimal residual disease diagnostics in acute lymphoblastic leukemia: need for sensitive, fast, and standardized technologies

Monitoring of minimal residual disease (MRD) has become routine clinical practice in frontline treatment of virtually all childhood acute lymphoblastic leukemia (ALL) and in many adult ALL patients. MRD diagnostics has proven to be the strongest prognostic factor, allowing for risk group assignment into different treatment arms, ranging from significant treatment reduction to mild or strong intensification. Also in relapsed ALL patients and patients undergoing stem cell transplantation, MRD diagnostics is guiding treatment decisions. This is also why the efficacy of innovative drugs, such as antibodies and small molecules, are currently being evaluated with MRD diagnostics within clinical trials. In fact, MRD measurements might well be used as a surrogate end point, thereby significantly shortening the follow-up. The MRD techniques need to be sensitive (≤10(-4)), broadly applicable, accurate, reliable, fast, and affordable. Thus far, flow cytometry and polymerase chain reaction (PCR) analysis of rearranged immunoglobulin and T-cell receptor genes (allele-specific oligonucleotide [ASO]-PCR) are claimed to meet these criteria, but classical flow cytometry does not reach a solid 10(-4), whereas classical ASO-PCR is time-consuming and labor intensive. Therefore, 2 high-throughput technologies are being explored, ie, high-throughput sequencing and next-generation (multidimensional) flow cytometry, both evaluating millions of sequences or cells, respectively. Each of them has specific advantages and disadvantages.

Thiopurine methyltransferase and treatment outcome in the UK acute lymphoblastic leukaemia trial ALL2003

The influence of thiopurine methyltransferase (TPMT) genotype on treatment outcome was investigated in the United Kingdom childhood acute lymphoblastic leukaemia trial ALL2003, a trial in which treatment intensity was adjusted based on minimal residual disease (MRD). TPMT genotype was measured in 2387 patients (76% of trial entrants): 2190 were homozygous wild-type, 189 were heterozygous for low activity TPMT alleles (166 TPMT*1/*3A, 19 TPMT*1/*3C, 3 TPMT*1/*2 and 1 TPMT*1/*9) and 8 were TPMT deficient. In contrast to the preceding trial ALL97, there was no difference in event-free survival (EFS) between the TPMT genotypes. The 5-year EFS for heterozygous TPMT*1/*3A patients was the same in both trials (88%), but for the homozygous wild-type TPMT*1/*1 patients, EFS improved from 80% in ALL97% to 88% in ALL2003. Importantly, the unexplained worse outcome for heterozygous TPMT*1/*3C patients observed in ALL97 (5-year EFS 53%) was not seen in ALL2003 (5-year EFS 94%). In a multivariate Cox regression analysis the only significant factor affecting EFS was MRD status (hazard ratio for high-risk MRD patients 4·22, 95% confidence interval 2·97–5·99, P < 0·0001). In conclusion, refinements in risk stratification and treatment have reduced the influence of TPMT genotype on treatment outcome in a contemporary protocol.

Survival of Mexican Children with Acute Lymphoblastic Leukaemia under Treatment with the Protocol from the Dana-Farber Cancer Institute 00-01

Our aim in this paper is to describe the results of treatment of acute lymphoblastic leukaemia (ALL) in Mexican children treated from 2006 to 2010 under the protocol from the Dana-Farber Cancer Institute (DFCI) 00-01. The children were younger than 16 years of age and had a diagnosis of ALL de novo. The patients were classified as standard risk if they were 1–9.9 years old and had a leucocyte count <50 × 10⁹/L, precursor B cell immunophenotype, no mediastinal mass, CSF free of blasts, and a good response to prednisone. The rest of the patients were defined as high risk. Of a total of 302 children, 51.7% were at high risk. The global survival rate was 63.9%, and the event-free survival rate was 52.3% after an average follow-up of 3.9 years. The percentages of patients who died were 7% on induction and 14.2% in complete remission; death was associated mainly with infection (21.5%). The relapse rate was 26.2%. The main factor associated with the occurrence of an event was a leucocyte count >100 × 10⁹/L. The poor outcomes were associated with toxic death during induction, complete remission, and relapse. These factors remain the main obstacles to the success of this treatment in our population.

Serum galactomannan screening for diagnosis of invasive pulmonary aspergillosis in children after stem cell transplantation or with high-risk leukemia

Both transplanted and leukemia patients are at high risk (HR) for invasive pulmonary aspergillosis (IPA). Methods for rapid diagnosis are crucial. Our objective was to investigate the impact of serial serum galactomannan assay (GMA) screening on IPA diagnosis in children. Between January 2010 and December 2011, all children following stem cell transplantation (SCT) or with HR leukemia were prospectively included. Serum samples for GMA were taken once-twice weekly. Results >.5 were considered positive. Patients suspected of having IPA were stratified as possible, probable, and definite. Forty-six children (median age, 8 years) were included, 38 after SCT (32 allogeneic), 8 with HR leukemia. A total of 510 samples were taken; screening period was 1-6 months for 34 patients. GMA was negative in 28 patients, all but one without suspicion of IPA. Eighteen patients had positive GMA: while four (22%) were upgraded to probable IPA, fourteen (78%) were considered as false positives (FP), some associated with piperacillin-tazobactam treatment. GMA sensitivity and specificity were 0.8 and 0.66, respectively; positive- and negative-predictive values (PPV, NPV) were 0.22 and 0.96, respectively. GMA may have a role in evaluating HR children for IPA. Both NPV and FP rates are high. The cost benefit of early detection versus over-diagnosis should be further studied.