Search

Purpose Minimal residual disease (MRD) and genetic abnormalities are important risk factors for outcome in acute lymphoblastic leukemia. Current risk algorithms dichotomize MRD data and do not assimilate genetics when assigning MRD risk, which reduces predictive accuracy. The aim of our study was to exploit the full power of MRD by examining it as a continuous variable and to integrate it with genetics. Patients and Methods We used a population-based cohort of 3,113 patients who were treated in UKALL2003, with a median follow-up of 7 years. MRD was evaluated by polymerase chain reaction analysis of Ig/TCR gene rearrangements, and patients were assigned to a genetic subtype on the basis of immunophenotype, cytogenetics, and fluorescence in situ hybridization. To examine response kinetics at the end of induction, we log-transformed the absolute MRD value and examined its distribution across subgroups. Results MRD was log normally distributed at the end of induction. MRD distributions of patients with distinct genetic subtypes were different ( P < .001). Patients with good-risk cytogenetics demonstrated the fastest disease clearance, whereas patients with high-risk genetics and T-cell acute lymphoblastic leukemia responded more slowly. The risk of relapse was correlated with MRD kinetics, and each log reduction in disease level reduced the risk by 20% (hazard ratio, 0.80; 95% CI, 0.77 to 0.83; P < .001). Although the risk of relapse was directly proportional to the MRD level within each genetic risk group, absolute relapse rate that was associated with a specific MRD value or category varied significantly by genetic subtype. Integration of genetic subtype-specific MRD values allowed more refined risk group stratification. Conclusion A single threshold for assigning patients to an MRD risk group does not reflect the response kinetics of the different genetic subtypes. Future risk algorithms should integrate genetics with MRD to accurately identify patients with the lowest and highest risk of relapse.

High-throughput sequencing (HTS) (next-generation sequencing) of the rearranged Ig and T-cell receptor genes promises to be less expensive and more sensitive than current methods of monitoring minimal residual disease (MRD) in patients with acute lymphoblastic leukemia. However, the adoption of new approaches by clinical laboratories requires careful evaluation of all potential sources of error and the development of strategies to ensure the highest accuracy. Timely and efficient clinical use of HTS platforms will depend on combining multiple samples (multiplexing) in each sequencing run. Here we examine the Ig heavy-chain gene HTS on the Illumina MiSeq platform for MRD. We identify errors associated with multiplexing that could potentially impact the accuracy of MRD analysis. We optimize a strategy that combines high-purity, sequence-optimized oligonucleotides, dual indexing, and an error-aware demultiplexing approach to minimize errors and maximize sensitivity. We present a probability-based, demultiplexing pipeline Error-Aware Demultiplexer that is suitable for all MiSeq strategies and accurately assigns samples to the correct identifier without excessive loss of data. Finally, using controls quantified by digital PCR, we show that HTS-MRD can accurately detect as few as 1 in 10(6) copies of specific leukemic MRD., (Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.)

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., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Background: Minimal residual disease (MRD) is the most sensitive and specific predictor of relapse risk in children with acute lymphoblastic leukaemia (ALL) during remission. We assessed whether treatment intensity could be adjusted for children and young adults according to MRD risk stratification., Methods: Between Oct 1, 2003 and June 30, 2011, consecutive children and young adults (aged 1-25 years) with ALL from the UK and Ireland were recruited. Eligible patients were categorised into clinical standard, intermediate, and high risk groups on the basis of a combination of National Cancer Institute (NCI) criteria, cytogenetics, and early response to induction therapy, which was assessed by bone marrow blast counts taken at days 8 (NCI high-risk patients) and 15 (NCI standard-risk patients) after induction began. Clinical standard-risk and intermediate-risk patients were assessed for MRD. Those classified as MRD low risk (undetectable MRD at the end of induction [day 29] or detectable MRD at day 29 that became undetectable by week 11) were randomly assigned to receive one or two delayed intensification courses. Patients had received induction, consolidation, and interim maintenance therapy before they began delayed intensification. Delayed intensification consisted of pegylated asparaginase on day 4; vincristine, dexamethasone (alternate weeks), and doxorubicin for 3 weeks; and 4 weeks of cyclophosphamide and cytarabine. Computer randomisation was done with stratification by MRD result and balancing for sex, age, and white blood cell count at diagnosis by method of minimisation. Patients, clinicians, and data analysts were not masked to treatment allocation. The primary outcome was event-free survival (EFS), which was defined as time to relapse, secondary tumour, or death. Our aim was to rule out a 7% reduction in EFS in the group given one delayed intensification course relative to that given two delayed intensification courses. Analyses were by intention to treat. This trial is registered, number ISRCTN07355119., Findings: Of 3207 patients registered in the trial overall, 521 MRD low-risk patients were randomly assigned to receive one (n=260) or two (n=261) delayed intensification courses. Median follow-up of these patients was 57 months (IQR 42-72). We recorded no significant difference in EFS between the group given one delayed intensification (94·4% at 5 years, 95% CI 91·1-97·7) and that given two delayed intensifications (95·5%, 92·8-98·2; unadjusted odds ratio 1·00, 95% CI 0·43-2·31; two-sided p=0·99). The difference in 5-year EFS between the two groups was 1·1% (95% CI -5·6 to 2·5). 11 patients (actuarial relapse at 5 years 5·6%, 95% CI 2·3-8·9) given one delayed intensification and six (2·4%, 0·2-4·6) given two delayed intensifications relapsed (p=0·23). Three patients (1·2%, 0-2·6) given two delayed intensifications died of treatment-related causes compared with none in the group given one delayed intensification (p=0·08). We recorded no significant difference between groups for serious adverse events and grade 3 or 4 toxic effects; however, the second delayed intensification course was associated with one (<1%) treatment-related death, and 74 episodes of grade 3 or 4 toxic effects in 45 patients (17%)., Interpretation: Treatment reduction is feasible for children and young adults with ALL who are predicted to have a low risk of relapse on the basis of rapid clearance of MRD by the end of induction therapy., Funding: Medical Research Council and Leukaemia and Lymphoma Research., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Minimal residual disease detection, used for clinical management of children with acute lymphoblastic leukemia, can be performed by molecular analysis of antigen-receptor gene rearrangements or by flow cytometric analysis of aberrant immunophenotypes. For flow minimal residual disease to be incorporated into larger national and international trials, a quality assured, standardized method is needed which can be performed in a multi-center setting. We report a four color, flow cytometric protocol established and validated by the UK acute lymphoblastic leukemia Flow minimal residual disease group. Quality assurance testing gave high inter-laboratory agreement with no values differing from a median consensus value by more than one point on a logarithmic scale. Prospective screening of B-ALL patients (n=206) showed the method was applicable to 88.3% of patients. The minimal residual disease in bone marrow aspirates was quantified and compared to molecular data. The combined risk category concordance (minimal residual disease levels above or below 0.01%) was 86% (n=134). Thus, this standardized protocol is highly reproducible between laboratories, sensitive, applicable, and shows good concordance with molecular-based analysis.

The continued improvement in the prognosis of childhood acute myeloid leukaemia (AML) has been paralleled by the use of increasingly intensive therapy. This has led to attempts to develop risk-directed strategies in which the most intensive treatment is reserved for those at highest risk of relapse. Unfortunately, current approaches, which rely on cytogenetic sub-grouping and morphological assessment of response to therapy, are inaccurate. New prognostic factors are needed. This annotation proposes that the introduction of protocols based on the measurement of minimal residual disease (MRD) holds the key to progression from an era of 'cure at all costs' to a more individualised approach. However, the full potential of MRD technologies will only be realised through properly designed studies with scrupulous attention to logistics and quality assurance. The article illustrates which children may benefit most from MRD analysis in AML and explores practical issues that should be addressed in the design of clinical trials.