Precise quantification of minimal residual disease at day 29 allows identification of children with acute lymphoblastic leukemia and an excellent outcome

Post-Induction Minimal Residual Disease in Pediatric Pre-B-Cell Acute Lymphoblastic Leukemia: A Step Towards Precision Medicine?

Background

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy with an incidence of 30% of pediatric cancers across the world and 34% amongst Saudi children with cancers. Minimal residual disease (MRD) is considered the most important independent predictor in determining the risk of relapse and long-term outcomes in ALL patients and plays a pivotal role in guiding risk-adapted therapies. The aim of this research was to study the role of MRD on survival benefits in our patient population.

Methods

We reviewed medical records of 108 pediatric (age ≤ 14 years) ALL patients treated between January 2016 and December 2018 at our center to assess if MRD and other associated risk factors affect the outcome of patients at post-induction and post-consolidation phases of the treatment protocols.

Results

The median follow-up time in our cohort of patients was 75.6 months (95% confidence interval: 71.3 - 79.8 months). With a mortality rate of 10.2% (11 deaths out of 108 cases), overall survival (OS) of the whole cohort was 89.2±3.1%. OS was significantly lower in post-induction MRD-positive cases than in MRD-negative cases (74.2±8.6% vs. 94.7±2.6%, P = 0.006). It was worse among those patients who underwent consolidation therapy and had positive post-consolidation MRD. Event-free survival (EFS) was also significantly poor in post-induction MRD-positive cases (61.1±10.2% vs. 92.1±3.1%, P = 0.001). Twenty-seven patients who received consolidation therapy had the poorest EFS (P = 0.031). Amongst all the factors, including age at diagnosis, gender, white blood cell count, central nervous system status, risk group or cytogenetics, only post-induction MRD positivity was found to be significantly associated with OS.

Conclusion

Post-induction MRD is one of the most important factors affecting the patient's outcome. Post-induction MRD-positive patients fared better after receiving consolidation therapy. No significant association was found between post-induction MRD and other risk factors.

Single-cell DNA and surface protein characterization of high hyperdiploid acute lymphoblastic leukemia at diagnosis and during treatment

High hyperdiploid (HeH) B-cell acute lymphoblastic leukemia (B-ALL) is the most prevalent subtype of childhood ALL. This leukemia is characterized by trisomies and tetrasomies of specific chromosomes and additional point mutations. Here, we used single-cell targeted DNA and antibody sequencing to determine the clonal evolution of HeH B-ALL during development and chemotherapy treatment. Chromosomal copy number changes were mostly stable over all the leukemia cells, while mutations were typically subclonal. Within all 13 cases, at least one RAS mutant (KRAS or NRAS) subclone was detected (range: 1 to 4 subclones with RAS mutations), indicating the importance of RAS signaling in HeH B-ALL development. NSD2 mutations were detected in 4 out of 13 cases and always in a subclone with RAS signaling mutations. Single-cell DNA sequencing detected residual leukemia cells during chemotherapy treatment, and analysis of chromosomal copy number changes aided in the accurate detection of these cells. Our single-cell data demonstrate that chromosomal changes are acquired prior to additional mutations and that RAS signaling mutations are present in all HeH cases, often as subclonal mutations. This single-cell multi-omics study enabled us to extensively characterize the genetic and surface protein heterogeneity in patients with HeH B-ALL.

Lymphocyte subsets in pediatric acute lymphoblastic leukemia and their prognostic value

To study the changes of lymphocyte subsets in children with acute lymphoblastic leukemia (ALL) at initial diagnosis and compare them with those of healthy children and patients who have achieved complete remission (CR). Furthermore, we aim to analyze the prognostic significance of lymphocyte subsets in these patients. From May 2011 to December 2015, 405 children with ALL were enrolled in this study. Peripheral blood was collected at the time of diagnosis, and lymphocyte subsets were detected by flow cytometry. Then, the percentages of lymphocyte subsets in each group were compared. In addition, survival and prognostic factor analyses were performed to determine the prognostic value of lymphocyte subsets. Lymphocyte subsets in children with ALL were dramatically different from those in healthy children and patients achieving CR. Additionally, lymphocyte subsets were correlated with different minimal residual disease and risk parameters. Furthermore, percentages of CD3+ T cells and CD4+ T cells and the ratio of CD4/CD8 were associated with different clinical outcomes. Multivariate analysis demonstrated the percentage of CD4+ T cell as an independent predictor for clinical prognosis. Lymphocyte subsets in pediatric ALL undergo dramatic changes and were related to prognosis, especially CD4+ T cells.

Remission, treatment failure, and relapse in pediatric ALL: an international consensus of the Ponte-di-Legno Consortium

Comparison of treatment strategies in de novo pediatric acute lymphoblastic leukemia (ALL) requires standardized measures of efficacy. Key parameters that define disease-related events, including complete remission (CR), treatment failure (TF; not achieving CR), and relapse (loss of CR) require an updated consensus incorporating modern diagnostics. We collected the definitions of CR, TF, and relapse from recent and current pediatric clinical trials for the treatment of ALL, including the key components of response evaluation (timing, anatomic sites, detection methods, and thresholds) and found significant heterogeneity, most notably in the definition of TF. Representatives of the major international ALL clinical trial groups convened to establish consensus definitions. CR should be defined at a time point no earlier than at the end of induction and should include the reduction of blasts below a specific threshold in bone marrow and extramedullary sites, incorporating minimal residual disease (MRD) techniques for marrow evaluations. TF should be defined as failure to achieve CR by a prespecified time point in therapy. Relapse can only be defined in patients who have achieved CR and must include a specific threshold of leukemic cells in the bone marrow confirmed by MRD, the detection of central nervous system leukemia, or documentation of extramedullary disease. Definitions of TF and relapse should harmonize with eligibility criteria for clinical trials in relapsed/refractory ALL. These consensus definitions will enhance the ability to compare outcomes across pediatric ALL trials and facilitate development of future international collaborative trials.

Clofarabine added to intensive treatment in adult patients with newly diagnosed ALL: the HOVON-100 trial

Clofarabine (CLO) is a nucleoside analogue with efficacy in relapsed/refractory acute lymphoblastic leukemia (ALL). This randomized phase III study aimed to evaluate whether CLO added to induction and consolidation would improve outcome in adults with newly diagnosed ALL. Treatment for younger (18-40 years) patients consisted of a pediatric inspired protocol and for older patients (41-70 years) of a semi-intensive protocol was used. 340 patients were randomized. After a median follow up of 70 months, 5-year EFS was 50% and 53% for arm A and B (CLO arm). For patients ≤40 years, EFS was 58% vs 65% in arm A vs B, while in patients >40 years EFS was 43% in both arms. CR rate was 89% in both arms and similar in younger and older patients. Minimal residual disease (MRD) was assessed in 200 patients (60%). Fifty-four of 76 evaluable patients (71%) were MRD negative after consolidation 1 in arm A vs 75/81 (93%) in arm B (p=0.001). Seventy (42%) patients proceeded to allogeneic hematopoietic stem cell transplantation in both arms. Five years OS was similar in both arms, 60% vs 61%. Among patients achieving CR, relapse rates were 28% and 24%, and non-relapse mortality was 16% vs 17% after CR. CLO treated patients experienced more serious adverse events, more infections, and more often went off-protocol. This was most pronounced in older patients. We conclude that, despite a higher rate of MRD-negativity, addition of CLO does not improve outcome in adults with ALL, which might be due to increased toxicity. The trial is registered at www.trialregister.nl as NTR2004.

Late adverse effects of childhood acute lymphoblastic leukemia treatment on developing dentition

BACKGROUND

Childhood cancer survivors show a variety of late adverse effects on dental health. The purpose of this study was to examine the prevalence and severity of dental abnormalities in permanent dentition in childhood leukemia survivors.

MATERIALS AND METHODS

Retrospective analysis of panoramic radiographs was performed for 178 childhood leukemia survivors aged below 17 years at the time of diagnosis. Sex, age at diagnosis, interval between ALL diagnosis and the follow-up radiograph, treatment protocol, and risk grouping were recorded. Abnormalities of tooth development and defect index were used to assess the frequency and severity of dental abnormalities.

RESULTS

One hundred eight (61%) patients had no dental abnormalities at follow-up examination at a median of 6.1 years after diagnosis. Microdontia was more frequent in children under 6 years of age at the time of diagnosis (5.7% vs. 0.6%, p < .001). Significant differences were noted between distinct ALL treatment protocols with more common microdontia in patients treated according to the NOPHO ALL2008 protocol. Tooth agenesis was more frequent in patients that underwent therapy according to high-risk arms compared to intermediate- or standard-risk arms (3.8% vs. 1.4%, p = .01). Patients under 6 years of age at diagnosis had a significantly higher average defect index score than older patients (7.0 vs. 2.8, p = .01).

CONCLUSIONS

Children and adolescents who received ALL treatment were at risk for dental damage. Young age and high-intensity therapy were associated with the severity of dental abnormalities.

Clinical features and outcome of pediatric acute lymphoblastic leukemia with low peripheral blood blast cell count at diagnosis

Peripheral blood (PB) blast cell count on day 8 of prednisone therapy has been considered one of the strongest predictors of outcome in children with acute lymphoblastic leukemia (ALL). However, little is known about the clinical features and prognostic impact of PB blast cell count at diagnosis in these patients. The aim of this study was to evaluate the relationship between initial PB blast cell count and clinical prognosis of pediatric ALL.The study comprised 367 patients with ALL, aged 0 to 14 years, enrolled and treated using the Chinese Children's Leukemia Group-ALL 2008 protocol between 2011 and 2015. The majority (91.6%) of patients were B-cell precursor ALL (BCP ALL), and 8.4% were T-cell ALL (T-ALL).Patients with BCP ALL in the low PB blast cell count group (<1 × 109/L) had significantly superior survival rates to those in the high count group (≥30 × 109/L). In T-ALL, the low count group showed significantly inferior survival rates compared to both the intermediate count group (1-29.9 × 109/L) and high count group. Multivariate analysis revealed that the initial white blood cell count and minimal residual disease at the end of induction therapy were independently predictive of BCP ALL outcome, while risk stratification was shown to be an independent prognostic factor for T-ALL outcome.These results indicated that low blast cell count in PB at diagnosis was associated with different clinical outcomes in patients with BCP ALL and T-ALL, although it was not an independent outcome predictor by multivariate analysis.

Prognostic Nomogram for Childhood Acute Lymphoblastic Leukemia: A Comprehensive Analysis of 673 Patients

OBJECTIVE

Despite that the survival rate in childhood acute lymphoblastic leukemia (cALL) is excellent, subsets of high-risk patients with cALL still have high relapse rates, and the cure rate is well below that for which we should aim. The present study aims to construct a prognostic nomogram to better inform clinical practitioners and improve risk stratification for clinical trials.

METHODS

The developed nomogram was based on the therapeutically applicable research to generate effective treatment (TARGET) database. With this database, we obtained 673 cALL patients with complete clinical information. We identified and integrated significant prognostic factors to build the nomogram model by univariate and multivariate Cox analysis. The predictive accuracy and discriminative ability of the nomogram were determined by the concordance index (C-index), calibration curve, and area under the receiver operating characteristic (ROC) curve (AUC) of ROC analysis. Internal validations were assessed by the bootstrapping validation.

RESULTS

In the multivariate analysis of the primary cohort, the independent factors for survival were ETV6 RUNX1 fusion status, karyotype, minimal residual disease (MRD) at day 29, and DNA index, which were all integrated into the nomogram. The calibration curve for the probability of survival showed good agreement between the prediction by the nomogram and the actual observation. The C-index of the nomogram for predicting survival was 0.754 (95% CI, 0.715-0.793), and the AUCs for 3-, 5-, and 7-year survival were 0.775, 0.776, and 0.772, respectively.

CONCLUSION

We comprehensively evaluated the risk of clinical factors associated with prognosis and carried out risk stratification. The nomogram proposed in this study objectively and accurately predicted the prognosis of children with ALL.

Bortezomib reinduction chemotherapy in high-risk ALL in first relapse: a report from the Children's Oncology Group

While survival in paediatric acute lymphoblastic leukaemia (ALL) is excellent, survival following relapse is poor. Previous studies suggest proteasome inhibition with chemotherapy improves relapse ALL response rates. This phase 2 Children's Oncology Group study tested the hypothesis that adding the proteasome inhibitor bortezomib to chemotherapy increases complete response rates (CR2). Evaluable patients (n = 135, 103 B-ALL, 22 T-ALL, 10 T-lymphoblastic lymphoma) were treated with reinduction chemotherapy plus bortezomib. Overall CR2 rates were 68 ± 5% for precursor B-ALL patients (<21 years of age), 63 ± 7% for very early relapse (<18 months from diagnosis) and 72 ± 6% for early relapse (18-36 months from diagnosis). Relapsed T-ALL patients had an encouraging CR2 rate of 68 ± 10%. End of induction minimal residual disease (MRD) significantly predicted survival. MRD negative (MRDneg; MRD <0·01%) rates increased from 29% (post-cycle 1) to 64% following cycle 3. Very early relapse, end-of-induction MRDneg precursor B-ALL patients had 70 ± 14% 3-year event-free (EFS) and overall survival (OS) rates, vs. 3-year EFS/OS of 0-3% (P = 0·0001) for MRDpos (MRD ≥0·01) patients. Early relapse patients had similar outcomes (MRDneg 3-year EFS/OS 58-65% vs. MRDpos 10-19%, EFS P = 0·0014). These data suggest that adding bortezomib to chemotherapy in certain ALL subgroups, such as T-cell ALL, is worthy of further investigation. This study is registered at http://www.clinical.trials.gov as NCT00873093.

Excellent outcome of minimal residual disease-defined low-risk patients is sustained with more than 10 years follow-up: results of UK paediatric acute lymphoblastic leukaemia trials 1997-2003

BACKGROUND

Minimal residual disease (MRD) is defined as the presence of sub-microscopic levels of leukaemia. Measurement of MRD from bone marrow at the end of induction chemotherapy (day 28) for childhood acute lymphoblastic leukaemia (ALL) can highlight a large group of patients (>40%) with an excellent (>90%) short-term event-free survival (EFS). However, follow-up in recent published trials is relatively short, raising concerns about using this result to infer the safety of further therapy reduction in the future.

METHODS

We examined MRD data on 225 patients treated on one of three UKALL trials between 1997 and 2003 to assess the long-term (>10 years follow-up) outcome of those patients who had low-risk MRD (<0.01%) at day 28.

RESULTS

Our pilot data define a cohort of 53% of children with MRD <0.01% at day 28 who have an EFS of 91% and long-term overall survival of 97%. Of 120 patients with day-28 MRD <0.01% and extended follow-up, there was one death due to treatment-related toxicity, one infectious death while in complete remission, and four relapse deaths.

CONCLUSIONS

The excellent outcome for childhood ALL in patients with MRD <0.01% after induction chemotherapy is sustained for more than 10 years from diagnosis. This supports the potential exploration of further reduction of therapy in this group, in an attempt to reduce treatment-related mortality and late effects.

Blinatumomab

Objective: To review the clinical pharmacology, efficacy, and safety of blinatumomab for the treatment of pediatric and adult precursor B-cell acute lymphoblastic leukemia (B-ALL). Data Sources: A literature search of EMBASE (1947 to April 2015), Medline (1946 to April 2015), PubMed (1996 to April 2015), the U.S. National Institutes of Health Clinicaltrials.gov, the Food and Drug Administration, and relevant meeting abstracts was conducted using the terms blinatumomab, BiTE, bispecific T-cell engager, MT103, MEDI-538, and Blincyto. Study Selection/Data Extraction: Human and animal studies describing the pharmacology, pharmacokinetics and pharmacodynamics, efficacy, and safety of blinatumomab for precursor B-ALL were identified. Data Synthesis: Blinatumomab is a first-in-class bispecific T-cell engager (BiTE) antibody derived from a B-lineage specific antitumor mouse monoclonal antibody that binds to both CD19 of B-cells and CD3 of T-cells. A pivotal phase II trial demonstrated that response rates were high in a refractory or relapsed patient population, with 43% achieving complete remission (CR). Median relapse-free survival was 5.9 months for those with CR or CR with incomplete hematological recovery. Median overall survival was 6.1 months, and 60% of patients achieved minimal residual disease (MRD) negativity. The most common adverse events included pyrexia, neurological events, headache, febrile neutropenia, peripheral edema, nausea, hypokalemia, constipation, and anemia. Conclusions: Blinatumomab is a novel BiTE therapeutic monoclonal antibody that has shown promising results in patients with relapsed or refractory ALL or those achieving a CR with persistent MRD. Phase III clinical trials should define the optimal place in therapy of blinatumomab.

Reprint of: Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

Minimal residual disease in acute lymphoblastic leukemia: optimal methods and clinical relevance, pitfalls and recent approaches

After advances in experimental and clinical testing, minimal residual disease (MRD) assay results are considered a determining factor in treatment of acute lymphoblastic leukemia patients. According to MRD assay results, bone marrow (BM) leukemic burden and the rate of its decline after treatment can be directly evaluated. Detailed knowledge of the leukemic burden in BM can minimize toxicity and treatment complications in patients by tailoring the therapeutic dose based on patients' conditions. In addition, reduction of MRD before allo-HSCT is an important prerequisite for reception of transplant by the patient. In direct examination of MRD by morphological methods (even by a professional hematologist), leukemic cells can be under- or over-estimated due to similarity with hematopoietic precursor cells. As a result, considering the importance of MRD, it is necessary to use other methods including flow cytometry, polymerase chain reaction (PCR) amplification and RQ-PCR to detect MRD. Each of these methods has its own advantages and disadvantages in terms of accuracy and sensitivity. In this review article, different MRD assay methods and their sensitivity, correlation of MRD assay results with clinical symptoms of the patient as well as pitfalls in results of these methods are evaluated. In the final section, recent advances in MRD have been addressed.

Mercaptopurine/Methotrexate maintenance therapy of childhood acute lymphoblastic leukemia: clinical facts and fiction

The antileukemic mechanisms of 6-mercaptopurine (6MP) and methotrexate (MTX) maintenance therapy are poorly understood, but the benefits of several years of myelosuppressive maintenance therapy for acute lymphoblastic leukemia are well proven. Currently, there is no international consensus on drug dosing. Because of significant interindividual and intraindividual variations in drug disposition and pharmacodynamics, vigorous dose adjustments are needed to obtain a target degree of myelosuppression. As the normal white blood cell counts vary by patients' ages and ethnicity, and also within age groups, identical white blood cell levels for 2 patients may not reflect the same treatment intensity. Measurements of intracellular levels of cytotoxic metabolites of 6MP and MTX can identify nonadherent patients, but therapeutic target levels remains to be established. A rise in serum aminotransferase levels during maintenance therapy is common and often related to high levels of methylated 6MP metabolites. However, except for episodes of hypoglycemia, serious liver dysfunction is rare, the risk of permanent liver damage is low, and aminotransferase levels usually normalize within a few weeks after discontinuation of therapy. 6MP and MTX dose increments should lead to either leukopenia or a rise in aminotransferases, and if neither is experienced, poor treatment adherence should be considered. The many genetic polymorphisms that determine 6MP and MTX disposition, efficacy, and toxicity have precluded implementation of pharmacogenomics into treatment, the sole exception being dramatic 6MP dose reductions in patients who are homozygous deficient for thiopurine methyltransferase, the enzyme that methylates 6MP and several of its metabolites. In conclusion, maintenance therapy is as important as the more intensive and toxic earlier treatment phases, and often more challenging. Ongoing research address the applicability of drug metabolite measurements for dose adjustments, extensive host genome profiling to understand diversity in treatment efficacy and toxicity, and alternative thiopurine dosing regimens to improve therapy for the individual patient.

Clinical features and early treatment response of central nervous system involvement in childhood acute lymphoblastic leukemia

BACKGROUND

Central nervous system (CNS) involvement in childhood acute lymphoblastic leukemia (ALL) remains a therapeutic challenge.

PROCEDURE

To explore leukemia characteristics of patients with CNS involvement at ALL diagnosis, we analyzed clinical features and early treatment response of 744 patients on Nordic-Baltic trials. CNS status was classified as CNS1 (no CSF blasts), CNS2 (<5 leukocytes/µl CSF with blasts), CNS3 (≥5 leukocytes/µl with blasts or signs of CNS involvement), TLP+ (traumatic lumbar puncture with blasts), and TLP- (TLP with no blasts).

RESULTS

Patients with CNS involvement had higher leukocyte count compared with patients with CNS1 (P < 0.002). Patients with CNS3 more often had T-ALL (P < 0.001) and t(9;22)(q34;q11)[BCR-ABL1] (P < 0.004) compared with patients with CNS1. Among patients with CNS involvement headache (17%) and vomiting (14%) were most common symptoms. Symptoms or clinical findings were present among 27 of 54 patients with CNS3 versus only 7 of 39 patients with CNS2 and 15 of 75 patients with TLP+ (P < 0.001). The majority of patients with CNS involvement received additional induction therapy. The post induction bone marrow residual disease level did not differ between patients with CNS involvement and patients with CNS1 (P > 0.15). The 12-year event-free survival for patients with leukemic mass on neuroimaging did not differ from patients with negative or no scan (0.50 vs. 0.60; P = 0.7) or between patients with symptoms or signs suggestive of CNS leukemia and patients without such characteristics (0.50 vs. 0.61; P = 0.2).

CONCLUSION

CNS involvement at diagnosis is associated with adverse prognostic features but does not indicate a less chemosensitive leukemia.

Validation of DNA methylation biomarkers for diagnosis of acute lymphoblastic leukemia

BACKGROUND

DNA methylation biomarkers capable of diagnosis and subtyping have been found for many cancers. Fifteen such markers have previously been identified for pediatric acute lymphoblastic leukemia (ALL). Validation of these markers is necessary to assess their clinical utility for molecular diagnostics. Substantial efficiencies could be achieved with these DNA methylation markers for disease tracking with potential to replace patient-specific genetic testing.

METHODS

We evaluated DNA methylation of promoter regions of TLX3 (T-cell leukemia homeobox) and FOXE3 (forkhead box E3) in bone marrow biopsies from 197 patients classified as leukemic (n = 95) or clear of the disease (n = 102) by MALDI-TOF. Using a single nucleotide extension assay (methylSABER), we tested 10 bone marrow biopsies collected throughout the course of patient chemotherapy. Using reference materials, diagnostic thresholds and limits of detection were characterized for both methods.

RESULTS

Reliable detection of DNA methylation of TLX3 and FOXE3 segregated ALL from those clear of disease with minimal false-negative and false-positive results. The limit of detection with MALDI-TOF was 1000-5000 copies of methylated allele. For methylSABER, the limit of detection was 10 copies of methylated TLX3, which enabled monitoring of minimal residual disease in ALL patients.

CONCLUSIONS

Mass spectrometry procedures can be used to regionally multiplex and detect rare DNA methylation events, establish DNA methylation loci as clinically applicable biomarkers for disease diagnosis, and track pediatric ALL.

Clinical significance of minimal residual disease in young adults with standard-risk/Ph-negative precursor B-acute lymphoblastic leukemia: results of prospective study

Clinical risk classification is inaccurate in predicting outcome in adult patients with acute lymphoblastic leukemia (ALL), sometimes resulting in patients receiving inappropriate chemotherapy or stem cell transplantation. To identify complementary markers suitable for further treatment stratification in patients with standard-risk (SR)/philadelphia-negative (Ph-negative) precursor B-ALL, we evaluated the predictive value of minimal residual disease (MRD) after induction and consolidation chemotherapy in strictly defined SR/Ph-negative precursor B-ALL patients who were treated with a standard protocol using quantitative real-time polymerase chain reaction with the rearranged immunoglobulin heavy chain gene as a molecular marker. The cytologic complete response (CR) rate was 92.3 % after induction. At this time point, the molecular CR rate was 73.9%. Patients with molecular CR (MolCR) after induction had a significantly higher probability of disease-free survival (DFS; 78.8 vs 30.8%; P = .001) and of overall survival (OS; 82.4 vs 41.7%; P < .0001) compared to patients with molecular failure (MolFail). MRD at end consolidation had the same significance. Quantitative MRD assessment identified patients with MolFail after induction and/or consolidation as a high-risk group, with 3-year DFS and OS rates of 28.6 and 35.7%, respectively. Patients with MolCR after induction and consolidation were classified as low-risk and had 3-year DFS rate of 89.7% and OS rate of 93.3%. Thus, MRD quantification during treatment identified prognostic subgroups within the otherwise homogeneous SR/Ph-negative precursor B-ALL population who may benefit from individualized treatment.

Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

Detection of MRD may predict the outcome of patients with Philadelphia chromosome-positive ALL treated with tyrosine kinase inhibitors plus chemotherapy

From 2001 to 2011, 122 patients with newly diagnosed Philadelphia chromosome-positive acute lymphoblastic leukemia were treated with chemotherapy + imatinib (n = 54) or + dasatinib (n = 68). One hundred fifteen (94%) achieved complete remission (CR) including 101 patients who achieved it with only 1 induction course and had at least 1 minimal residual disease (MRD) assessment; 25 patients underwent an allogeneic stem cell transplant in first CR and were excluded, leaving 76 patients as the subject of this report. MRD monitoring by multiparameter flow cytometry (MFC) and real-time quantitative polymerase chain reaction (PCR) was performed at the end of induction and at ~3-month intervals thereafter. Median age was 54 years (range, 21-84 years). There was no difference in survival by achievement of at least a major molecular response (MMR; BCR-ABL/ABL < 0.1%) at CR (P = .22). Patients achieving MMR at 3, 6, 9, and 12 months had a better survival (P = .02, .04, .05, and .01, respectively). Negative MFC at CR did not predict for improved survival (P = .2). At 3 and 12 months, negative MRD by MFC was associated with improved survival (P = .04 and .001). MRD monitoring by PCR and MFC identifies patients who benefit from treatment intensification in first CR.

Leukemia surfaceome analysis reveals new disease-associated features

A better description of the leukemia cell surface proteome (surfaceome) is a prerequisite for the development of diagnostic and therapeutic tools. Insights into the complexity of the surfaceome have been limited by the lack of suitable methodologies. We combined a leukemia xenograft model with the discovery-driven chemoproteomic Cell Surface Capture technology to explore the B-cell precursor acute lymphoblastic leukemia (BCP-ALL) surfaceome; 713 cell surface proteins, including 181 CD proteins, were detected through combined analysis of 19 BCP-ALL cases. Diagnostic immunophenotypes were recapitulated in each case, and subtype specific markers were detected. To identify new leukemia-associated markers, we filtered the surfaceome data set against gene expression information from sorted, normal hematopoietic cells. Nine candidate markers (CD18, CD63, CD31, CD97, CD102, CD157, CD217, CD305, and CD317) were validated by flow cytometry in patient samples at diagnosis and during chemotherapy. CD97, CD157, CD63, and CD305 accounted for the most informative differences between normal and malignant cells. The ALL surfaceome constitutes a valuable resource to assist the functional exploration of surface markers in normal and malignant lymphopoiesis. This unbiased approach will also contribute to the development of strategies that rely on complex information for multidimensional flow cytometry data analysis to improve its diagnostic applications.

Retrospective monitoring of minimal residual disease using hairpin-shaped clone specific primers in B-cell lymphoma affected dogs

Lymphoma is one of the most common forms of cancer in dogs as it is in humans but, unlike humans, the cure rates in canines are still very low. Despite the fact that high grade B-cell lymphomas are considered to be chemotherapy responsive, almost all treated dogs ultimately relapse and die due to the residual malignant lymphocytes, namely minimal residual disease (MRD). It would be extremely valuable for clinicians to detect, monitor and quantify MRD for risk group stratification, effective treatment intervention and outcome prediction. The PCRs targeting the Ig gene rearrangements constitute one of the most reliable tools to this end. We have recently validated a method which exploits hairpin-shaped primers for quantifying MRD. In the present study, that method is conveniently used for retrospectively monitoring MRD in the peripheral blood of 8 dogs diagnosed with B-cell lymphoma who underwent chemotherapy. All dogs attained complete remission. The median disease-free interval was 254.5 days (range 63-774) while the median survival time was 313.5 days (range 143-817 days). At admission, all dogs, except one which had already been treated with prednisone, had circulating neoplastic cells. All dogs attained complete remission (CR) which was almost always matched with a complete MRD response. The persistence of MRD despite apparent CR indicated a worse prognosis and a short duration of CR. Finally, the relapse is consistently anticipated by the reappearance of MRD in the peripheral blood. The study confirmed the suitability of an MRD monitoring assay as a clinical decision-making tool.

Measurements of treatment response in childhood acute leukemia

Measuring response to chemotherapy is a backbone of the clinical management of patients with acute leukemia. This task has historically relied on the ability to identify leukemic cells among normal bone marrow cells by their morphology. However, more accurate ways to identify leukemic cells have been developed, which allow their detection even when they are present in small numbers that would be impossible to be recognized by microscopic inspection. The levels of such minimal residual disease (MRD) are now widely used as parameters for risk assignment in acute lymphoblastic leukemia (ALL) and increasingly so in acute myeloid leukemia (AML). However, different MRD monitoring methods may produce discrepant results. Moreover, results of morphologic examination may be in stark contradiction to MRD measurements, thus creating confusion and complicating treatment decisions. This review focusses on the relation between results of different approaches to measure response to treatment and define relapse in childhood acute leukemia.

The myth of the second remission of acute leukemia in the adult

Although the majority of adult patients with both acute lymphoblastic leukemia and acute myelogenous leukemia achieve remission with upfront chemotherapy, many patients still suffer relapse. Often, the strategy is proposed of treating patients with relapsed leukemia into a second remission (CR2) and then proceeding to allogeneic transplantation as the definitive curative approach. However, the long-term outcomes of such a strategy are poor: the 5-year overall survival from first relapse for patients with acute leukemia is only approximately 10%. This Perspective highlights the fact that most patients do not achieve CR2 and therefore never really have an opportunity for a potential curative therapy. Although patients who undergo transplantation after relapse may be cured, those who do not achieve CR2 are rarely candidates for transplantation; therefore, the overall outcome for patients who relapse is dismal. There is therefore an urgent need not only for more effective upfront therapy to prevent relapse, but also for the development of therapies that can serve as effective bridging treatments between relapse and transplantation. We suggest that more optimal use of minimal residual disease detection during first remission may also improve the chances for successful transplantation therapy via earlier reinduction therapy, allowing transplantation before overt relapse.

Minimal residual disease: optimal methods, timing, and clinical relevance for an individual patient

After approximately 20 years of development and after several prospective clinical trials, the detection of minimal residual disease (MRD) has emerged as part of state-of-the-art diagnostics to guide the majority of contemporary treatment programs both in pediatric and adult acute lymphoblastic leukemia (ALL). For ALL, several methods of MRD analysis are available, but 2 are widely applicable. One is based on the detection of aberrant expression of leukemia specific antigens by flow cytometry and the other one uses the specific rearrangements of the TCR or Ig genes, which can be detected by quantitative PCR in the DNA of leukemic cells. In some cases with known fusion genes such as BCR/ABL, RT-PCR can be used as a third method of identifying leukemic cells by analyzing RNA in patient samples. Clinical application of such sophisticated tools in the stratification and treatment of ALL requires reliable, reproducible, and quality-assured methods to ensure patient safety.

A highly sensitive and specific qPCR assay for quantification of the biomarker SOX11 in mantle cell lymphoma

OBJECTIVES

Mantle cell lymphoma (MCL) is one of the most heterogeneous lymphoid neoplasms with a variable course of disease. Although t(11;14)(q13;q32) is the hallmark of MCL resulting in cyclin D1 (CCND1) overexpression in 90% of patients, this is difficult to validate by immunohistochemistry. We hypothesised that SOX11 could be a robust molecular biomarker for MCL.

METHODS

We have developed very sensitive and specific RT-qPCR assay employing a poly-A specific RT primer to circumvent contamination from gDNA caused by the intron-less nature of SOX11.

RESULTS

We found a significant difference between the expression levels of SOX11 in patients with MCL at diagnosis (n = 21) and in healthy donors (n = 18) (blood: P < 0.0001; marrow: P = 0.0001). SOX11 expression of very low levels close to the assay sensitivity was detected in only 2 of 18 healthy donors, while low levels of CCND1 expression was observed in all blood and 12 of 13 marrow samples within the defined detection limit of Cq = 40. In spiking experiments of the GRANTA-519 MCL cell line into mononuclear cells from normal donor, the sensitivity of the SOX11 assay was found to be 2 × 10(-4) , while the sensitivity of the CCND1 assay was estimated to 2 × 10(-3) because of the normal background expression. In longitudinal sampling from patients with MCL the minimal residual disease (MRD) values based on the SOX11 expression mirrored the clinical disease development.

CONCLUSION

This SOX11 RT-qPCR assay could be a useful tool for MRD monitoring in patients with MCL.

Adult patients with acute lymphoblastic leukemia and molecular failure display a poor prognosis and are candidates for stem cell transplantation and targeted therapies

Quantification of minimal residual disease (MRD) by real-time PCR directed to TCR and Ig gene rearrangements allows a refined evaluation of response in acute lymphoblastic leukemia (ALL). The German Multicenter Study Group for Adult ALL prospectively evaluated molecular response after induction/consolidation chemotherapy according to standardized methods and terminology in patients with Philadelphia chromosome-negative ALL. The cytologic complete response (CR) rate was 89% after induction phases 1 and 2. At this time point the molecular CR rate was 70% in 580 patients with cytologic CR and evaluable MRD. Patients with molecular CR after consolidation had a significantly higher probability of continuous complete remission (CCR; 74% vs 35%; P < .0001) and of overall survival (80% vs 42%; P = .0001) compared with patients with molecular failure. Patients with molecular failure without stem cell transplantation (SCT) in first CR relapsed after a median time of 7.6 months; CCR and survival at 5 years only reached 12% and 33%, respectively. Quantitative MRD assessment identified patients with molecular failure as a new high-risk group. These patients display resistance to conventional drugs and are candidates for treatment with targeted, experimental drugs and allogeneic SCT. Molecular response was shown to be highly predictive for outcome and therefore constitutes a relevant study end point. The studies are registered at www.clinicaltrials.gov as NCT00199056 and NCT00198991.

Low platelet counts after induction therapy for childhood acute lymphoblastic leukemia are strongly associated with poor early response to treatment as measured by minimal residual disease and are prognostic for treatment outcome

BACKGROUND

Numerous reports have been published on the association between kinetics of leukemic cells during early treatment of childhood acute lymphoblastic leukemia and therapeutic outcome. In contrast, little is known about the prognostic relevance of normal blood counts in this setting.

DESIGN AND METHODS

Normal hematopoiesis during and after induction treatment (days 8, 15 and 33) was correlated with therapeutic outcome in a cohort of 256 children with acute lymphoblastic leukemia treated in one of three consecutive ALL-BFM trials at a single institute. Replication analysis of positive findings was performed in an independent cohort of 475 patients from the ALL-BFM 2000 multicenter trial.

RESULTS

A platelet count in the first quartile on treatment day 33 and a neutrophil count above the median on day 8 were significantly associated with treatment outcome, conferring multivariate risk ratios for an event of 3.27 (95% confidence interval 1.60-6.69) and 2.26 (95% confidence interval 1.23-4.29), respectively. Replication analysis confirmed the prognostic effect of platelet count on treatment day 33 and demonstrated a strong association with minimal residual disease-based risk group distribution (P<0.00001).

CONCLUSIONS

Platelet counts after induction treatment may improve treatment stratification for patients with childhood acute lymphoblastic leukemia and be of particular interest in non-minimal residual disease-based trials. (ALL-BFM 2000 is registered at: ClinicalTrials.gov: NCT00430118. National Cancer Institute: Protocol ID 68529).

Augmented therapy improves outcome for pediatric high risk acute lymphocytic leukemia: results of Children's Oncology Group trial P9906

BACKGROUND

The augmented BFM regimen improves outcome for children with NCI high acute lymphoblastic leukemia (ALL). Patient age, sex, and presenting white blood cell count (WBC) can be used to identify a subset of approximately 12% of children with B-precursor ALL that had a 5-year continuous complete remission (CCR) rate of only about 50% on earlier Pediatric Oncology Group (POG) trials.

PROCEDURES

Children's Oncology Group trial P9906 evaluated a modified augmented BFM regimen in 267 patients with particularly high risk B-precursor ALL. Minimal residual disease (MRD) was assessed in blood at day 8 and in marrow at day 29 of induction and correlated with outcome.

RESULTS

The 5-year CCR probability for patients in P9906 was significantly better than that observed for similar patients on POG trials 8602/9006 (62.2 ± 3.7% vs. 50.6 ± 2.4%; P = 0.0007) but similar to POG 9406 (63.5 ± 2.4%; P = 0.81). Interim analysis showed poor central nervous system (CNS) control, especially in patients with initial WBC ≥ 100,000/microliter. Day 29 marrow MRD positive (≥ 0.01%) vs. negative patients had 5 year CCR rates of 37.1 ± 7.4% vs. 72.6 ± 4.3%; day 8 blood MRD positive vs. negative patients had 5 year CCR rates of 57.1 ± 4.6% vs.83.6 ± 6.3%. End induction marrow MRD predicted marrow but not CNS relapse. In multivariate analysis, day 29 MRD > 0.01%, initial WBC ≥ 100,000/µl, male gender, and day 8 blood MRD > 0.01% were significant prognostic factors.

CONCLUSIONS

Augmented BFM therapy improved outcome for children with higher risk ALL. Day 8 blood and day 29 marrow MRD were strong prognostic factors in these patients.

Promotional etiology for common childhood acute lymphoblastic leukemia: the infective lymphoid recovery hypothesis

This paper speculates on the role of infection in modifying a young child's risk of promoting precursor B-cell acute lymphoblastic leukemia (ALL). It is suggested that the heat shock instigated by infections, particularly in infancy, stimulates Th1 pro-inflammatory cytokines and an apoptosis-inhibitory environment. This infective stress also increases the number of cooperating oncogenic mutations in pre-leukemic cells, especially if the primary adaptive immune response is delayed. The glucocorticoid release that follows leads to acute thymic involution, a decline in antitumor immunity, and maturation arrest of B-lymphocytes. The infective lymphoid recovery hypothesis addresses an apparent contradiction-that a non-hygienic environment primes the adaptive immune response and is protective against childhood ALL, while multiple infections occurring later increase the risk of childhood ALL. In affluent (compared to less-affluent) societies, the characteristic ALL incidence peak in early childhood, and the shortened time to diagnosis, arise from surviving recurrent infections and the accumulated loss and recovery of lymphoid tissue. Evidence supporting the hypothesis, such as the role of lymphoid tissue reconstitution cytokines that stimulate proliferation stress on B-cell progenitors, comes from the study of children with congenital syndromes that are susceptible to leukemia.

Prognostic value of MRD-dynamics in childhood acute lymphoblastic leukemia treated according to the MB-2002/2008 protocols

Detection of minimal residual disease (MRD) during the treatment of acute lymphoblastic leukemia (ALL) by RQ-PCR analysis of clonal Ig/TCR rearrangements is used for risk group stratification in European treatment protocols. In Belarus patients with childhood ALL are treated according to ALL-MB protocols, which do not use MRD-based risk stratification. To evaluate the prognostic significance of MRD for ALL-MB-2002/2008 protocols, MRD was quantified by RQ-PCR in 68 ALL patients at four time points: on day 15, on day 36, before and after maintenance therapy (MT). MRD positivity, as well as quantitative level of MRD were analyzed and compared between patients who stayed in remission and relapsed. Relapse-free survival revealed to be significantly associated with MRD levels at different time points. Unfavorable prognosis was shown for MRD≥10(-3) on day 36 (p<0.001), and any positive MRD before (p<0.001) and after (p=0.001) MT. Multivariate Cox regression analysis proved MRD as independent significant prognosis factor at day 36 (p=0.005) and before MT (p=0.001). We conclude, that MRD quantified by RQ-PCR in children with ALL treated with ALL-MB protocols is feasible and independently associated with outcome. MRD may be a suitable parameter for treatment stratification in MB protocols in future.

New markers for minimal residual disease detection in acute lymphoblastic leukemia

To identify new markers for minimal residual disease (MRD) detection in acute lymphoblastic leukemia (ALL), we compared genome-wide gene expression of lymphoblasts from 270 patients with newly diagnosed childhood ALL to that of normal CD19⁺CD10⁺ B-cell progenitors (n = 4). Expression of 30 genes differentially expressed by ≥ 3-fold in at least 25% of cases of ALL (or 40% of ALL subtypes) was tested by flow cytometry in 200 B-lineage ALL and 61 nonleukemic BM samples, including samples containing hematogones. Of the 30 markers, 22 (CD44, BCL2, HSPB1, CD73, CD24, CD123, CD72, CD86, CD200, CD79b, CD164, CD304, CD97, CD102, CD99, CD300a, CD130, PBX1, CTNNA1, ITGB7, CD69, CD49f) were differentially expressed in up to 81.4% of ALL cases; expression of some markers was associated with the presence of genetic abnormalities. Results of MRD detection by flow cytometry with these markers correlated well with those of molecular testing (52 follow-up samples from 18 patients); sequential studies during treatment and diagnosis-relapse comparisons documented their stability. When incorporated in 6-marker combinations, the new markers afforded the detection of 1 leukemic cell among 10(5) BM cells. These new markers should allow MRD studies in all B-lineage ALL patients, and substantially improve their sensitivity.

Noninvasive identification of subcellular organization and nuclear morphology features associated with leukemic cells using light-scattering spectroscopy

Leukemia is the most common and deadly cancer among children and one of the most prevalent cancers among adults. Improvements in its diagnosis and monitoring of leukemic patients could have a significant impact in their long-term treatment. We demonstrate that light-scattering spectroscopy (LSS)-based approaches could serve as a tool to achieve this goal. Specifically, we characterize the light scattering properties of leukemic (NALM-6) cells and compare them to those of normal lymphocytes and granulocytes in the 440-710 nm range, over ±4 deg about the exact backscattering direction. We find that the LSS spectra are well described by an inverse power-law wavelength dependence, with a power exponent insensitive to the scattering angle but significantly higher for leukemic cells than for normal leukocytes. This is consistent with differences in the subcellular morphology of these cells, detected in differential interference contrast images. Furthermore, the residual light-scattering signal, extracted after subtracting the inverse power-law fit from the data, can be analyzed assuming a Gaussian distribution of spherical scatterers using Mie theory. This analysis yields scatterer sizes that are consistent with the diameters of cell nuclei and allows the detection of the larger nuclei of NALM-6 cells compared to those of lymphocytes and granulocytes.

Minimal residual disease assessment in childhood acute lymphoblastic leukaemia: a Swedish multi-centre study comparing real-time polymerase chain reaction and multicolour flow cytometry

Minimal residual disease (MRD) assessment is a powerful prognostic factor for determining the risk of relapse in childhood acute lymphoblastic leukaemia (ALL). In this Swedish multi-centre study of childhood ALL diagnosed between 2002 and 2006, the MRD levels were analysed in 726 follow-up samples in 228 children using real-time quantitative polymerase chain reaction (RQ-PCR) of rearranged immunoglobulin/T-cell receptor genes and multicolour flow cytometry (FCM). Using an MRD threshold of 0·1%, which was the sensitivity level reached in all analyses, the concordance between RQ-PCR and FCM MRD values at day 29 was 84%. In B-cell precursor ALL, an MRD level of ≥0·1% at day 29 predicted a higher risk of bone marrow relapse (BMR) with both methods, although FCM was a better discriminator. However, considering the higher median MRD values achieved with RQ-PCR, a higher MRD cut-off (≥0·2%) improved the predictive capacity of RQ-PCR. In T-ALL, RQ-PCR was notably superior to FCM in predicting risk of BMR. That notwithstanding, MRD levels of ≥0·1%, detected by either method at day 29, could not predict isolated extramedullary relapse. In conclusion, the concordance between RQ-PCR and FCM was high and hence both methods are valuable clinical tools for identifying childhood ALL cases with increased risk of BMR.

Minimal residual disease-based augmented therapy in childhood acute lymphoblastic leukemia: a report from the Japanese Childhood Cancer and Leukemia Study Group

BACKGROUND

The majority of minimal residual disease (MRD)-positive patients with acute lymphoblastic leukemia (ALL) have poor outcomes. The ALL2000 study was performed to evaluate the efficacy of augmented chemotherapy based on MRD-restratification in childhood ALL.

PROCEDURE

Between 2000 and 2004, 305 eligible patients with precursor B or T-cell ALL were enrolled in the ALL2000 study. The ALL941-based therapy protocol utilized PCR MRD assays using Immunoglobulin and T-cell receptor gene rearrangements. They were initially stratified into three risk-groups according to leukocyte count and age, and MRD levels were measured at weeks 5 (TP1) and 12 (TP2) for a second stratification. From week 14, patients with MRD levels ≥ 10(-3) received an increase in therapy (one risk group higher), while the remainder continued to receive the initial risk-adapted therapy.

RESULTS

The overall 5-year event-free survival (EFS) rate for ALL2000 was 79.7 ± 2.4%. MRD stratification was feasible for 234 of 301 patients (77%) who achieved complete remission. The EFS rate of the MRD stratifiable (MRD) group was 82.5 ± 2.6%, considerably superior to the 74.7 ± 5.7% of MRD non-stratifiable (Non-MRD) group (P = 0.084) and the 74.4 ± 2.1% for ALL 941 (P = 0.012). MRD-positive patients at TP2 showed inferior outcomes as compared with MRD-negative cases, but the difference did not reach a statistically significant level in any risk groups or immunophenotypes.

CONCLUSIONS

These results suggest that augmented therapy for MRD-positive patients at TP2 contributed to better outcomes of the ALL2000 study.

A unique complex translocation involving six different chromosomes in a case of childhood acute lymphoblastic leukemia with the Philadelphia chromosome and adverse prognosis

Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Approximately 84% of cases of ALL are classified as B-precursor ALL, 14% of cases are T-cell and 2% of cases are B-cell (B-)ALL. About one third of B-ALL cases show an abnormal karyotype. Combining data obtained by immunophenotyping, karyotyping and molecular cytogenetic analyses allows for a better understanding of this heterogeneous disease. This study reports an exceptional B-ALL case with a poor prognosis and unique complex chromosomal aberrations not previously observed, i.e., a translocation involving the six chromosomal regions 1q42, 4q21, 4q24, 4q35 (twice), 8q22 and 10p15.3 besides 9q34 and 22q11.2.

Where can biology of childhood ALL be attacked by new compounds?

Although the majority of children with acute lymphoblastic leukemia (ALL) can be cured with combination chemotherapy, the challenge remains to salvage patients with resistant disease and to reduce treatment related toxicity. To meet this challenge, it will be essential to incorporate new agents targeting the biological Achilles Heels of this cancer more rapidly into currently available treatment regimen. Here we review the principles of current ALL therapy, recent advances in understanding ALL biology and discuss a selection of promising areas for drug development that may take advantage of the underlying leukemia biology. We focus particularly on strategies to interfere with common effector mechanisms that can be trigged by different individual oncogenic lesions and on new agents from drug development programs in adult oncology, as such agents will come with better chances for sustainable commercial development.

Molecular response to treatment redefines all prognostic factors in children and adolescents with B-cell precursor acute lymphoblastic leukemia: results in 3184 patients of the AIEOP-BFM ALL 2000 study

The Associazione Italiana di Ematologia Oncologia Pediatrica and the Berlin-Frankfurt-Münster Acute Lymphoblastic Leukemia (AIEOP-BFM ALL 2000) study has for the first time introduced standardized quantitative assessment of minimal residual disease (MRD) based on immunoglobulin and T-cell receptor gene rearrangements as polymerase chain reaction targets (PCR-MRD), at 2 time points (TPs), to stratify patients in a large prospective study. Patients with precursor B (pB) ALL (n = 3184) were considered MRD standard risk (MRD-SR) if MRD was already negative at day 33 (analyzed by 2 markers, with a sensitivity of at least 10(-4)); MRD high risk (MRD-HR) if 10(-3) or more at day 78 and MRD intermediate risk (MRD-IR): others. MRD-SR patients were 42% (1348): 5-year event-free survival (EFS, standard error) is 92.3% (0.9). Fifty-two percent (1647) were MRD-IR: EFS 77.6% (1.3). Six percent of patients (189) were MRD-HR: EFS 50.1% (4.1; P < .001). PCR-MRD discriminated prognosis even on top of white blood cell count, age, early response to prednisone, and genotype. MRD response detected by sensitive quantitative PCR at 2 predefined TPs is highly predictive for relapse in childhood pB-ALL. The study is registered at http://clinicaltrials.gov: NCT00430118 for BFM and NCT00613457 for AIEOP.

Standardized MRD quantification in European ALL trials: proceedings of the Second International Symposium on MRD assessment in Kiel, Germany, 18-20 September 2008

Assessment of minimal residual disease (MRD) has acquired a prominent position in European treatment protocols for patients with acute lymphoblastic leukemia (ALL), on the basis of its high prognostic value for predicting outcome and the possibilities for implementation of MRD diagnostics in treatment stratification. Therefore, there is an increasing need for standardization of methodologies and harmonization of terminology. For this purpose, a panel of representatives of all major European study groups on childhood and adult ALL and of international experts on PCR- and flow cytometry-based MRD assessment was built in the context of the Second International Symposium on MRD assessment in Kiel, Germany, 18-20 September 2008. The panel summarized the current state of MRD diagnostics in ALL and developed recommendations on the minimal technical requirements that should be fulfilled before implementation of MRD diagnostics into clinical trials. Finally, a common terminology for a standard description of MRD response and monitoring was established defining the terms 'complete MRD response', 'MRD persistence' and 'MRD reappearance'. The proposed MRD terminology may allow a refined and standardized assessment of response to treatment in adult and childhood ALL, and provides a sound basis for the comparison of MRD results between different treatment protocols.