Minimal residual disease detection in childhood acute lymphoblastic leukaemia patients at multiple time‐points reveals high levels of concordance between molecular and immunophenotypic approaches

Abstract

SummaryIn this single centre study of childhood acute lymphoblastic leukaemia (ALL) patients treated on the Medical Research Council UKALL 97/99 protocols, it was determined that minimal residual disease (MRD) detected by real time quantitative polymerase chain reaction (RQ-PCR) and 3-colour flow cytometry (FC) displayed high levels of qualitative concordance when evaluated at multiple time-points during treatment (93AE38%), and a combined use of both approaches allowed a multi timepoint evaluation of MRD kinetics for 90% (53/59) of the initial cohort. At diagnosis, MRD markers with sensitivity of at least 0AE01% were identified by RQ-PCR detection of fusion gene transcripts, IGH/TRG rearrangements, and FC. Using a combined RQ-PCR and FC approach, the evaluation of 367 follow-up BM samples revealed that the detection of MRD >1% at Day 15 (P = 0AE04), >0AE01% at the end of induction (P = 0AE02), >0AE01% at the end of consolidation (P = 0AE01), >0AE01% prior to the first delayed intensification (P = 0AE01), and >0AE1% prior to the second delayed intensification and continued maintenance (P = 0AE001) were all associated with relapse and, based on early time-points (end of induction and consolidation) a significant log-rank trend (P = 0AE0091) was noted between survival curves for patients stratified into high, intermediate and low-risk MRD groups.

Time point-dependent concordance of flow cytometry and real-time quantitative polymerase chain reaction for minimal residual disease detection in childhood acute lymphoblastic leukemia

“…Our results concur with those reported by Malec et al, 28 but contradict others of studies indicating a concordance higher than 90%. 26,27,29,30 Several differences between these studies and ours may explain this. Kerst et al 29 and Ryan et al 30 considered many fewer paired samples than we did in our multicenter study.…”

“…[26][27][28][29][30] By applying this criterion to our series, the overall concordance rate was 80%, with the lowest concordance rate at day 33 (70%). Our results concur with those reported by Malec et al, 28 but contradict others of studies indicating a concordance higher than 90%.…”

“…9,18 However, few studies have compared the MRD estimates obtained by the simultaneous application of FCM and PCR in therapeutic protocols and at specific time points. [26][27][28][29][30] Indeed, PCR and FCM MRD measurements may be combined for a better definition of the risk of treatment failure in children with ALL treated in a multicenter study. 31 Here we report the results of the contemporary application of FCM and PCR analysis to 3565 bone marrow samples.…”

Improved flow cytometric detection of minimal residual disease in childhood acute lymphoblastic leukemia

“…Several studies on direct comparison between FCM and molecular MRD data have been performed. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] Generally, when 3/4-color FCM MRD data are qualitatively compared with PCRbased MRD data (using 0.01% as cutoff), the reported concordance varies from 70% to over 95%, depending on the time point and the related MRD level. A true quantitative comparison using both approaches was performed in only four studies (including at least 20 patients) and in samples in which both methods detected MRD levels above 0.01%, a significant relation was observed.…”

Identification of residual leukemic cells by flow cytometry in childhood B-cell precursor acute lymphoblastic leukemia: verification of leukemic state by flow-sorting and molecular/cytogenetic methods

“…Both situations can lead to different treatment stratification depending on the MRD method used and the cut-off levels. [8][9][10][11] Despite this, the identification of malignant cells by FC has only been biologically verified in one study including 5 patients. 12 To explore the background of such discrepancies, we investigated 53 follow-up BM samples from 28 children with B-cell precursor ALL (BCP-ALL) by flow-sorting of immunophenotype-defined residual leukemic cell populations, and subsequent analyses for leukemia-associated genomic markers by Reduction in minimal residual disease, measured by real-time quantitative PCR or flow cytometry, predicts prognosis in childhood B-cell precursor acute lymphoblastic leukemia.…”