Summary
The prognostic value of minimal residual disease (MRD) measured by fusion‐gene transcript (FGT) detection was investigated in 76 infants (aged ≤1 year) with acute lymphoblastic leukaemia (ALL) with lysine methyltransferase 2A (KMT2A) rearrangements. Either at the end of induction or at later time‐points, FGT‐MRD‐positivity was associated with poor outcome. FGT‐MRD‐positivity after first consolidation or first high‐risk block detected 46·5% of infants with extremely poor outcome [disease‐free survival (SE) 0·06 (0·06), cumulative incidence of relapse (SE) 0·91 (0·05)], which was also confirmed in multivariable analysis. Thus, FGT‐MRD measurement at a single time‐point clearly identifies infants with ALL who are curable with conventional chemotherapy and those who would benefit only from other treatment approaches.
Summary
This study aimed to evaluate the concordance between minimal residual disease (MRD) results obtained by multicolour flow cytometry (MFC) and polymerase chain reaction for fusion gene transcripts (FGTs) in infants with acute lymphoblastic leukaemia (ALL) associated with rearrangement of the KMT2A gene (KMT2A‐r). A total of 942 bone marrow (BM) samples from 123 infants were studied for MFC‐MRD and FGT‐MRD. In total, 383 samples (40.7%) were concordantly MRD‐negative. MRD was detected by the two methods in 441 cases (46.8%); 99 samples (10.5%) were only FGT‐MRD‐positive and 19 (2.0%) were only MFC‐MRD‐positive. A final concordance rate of 87.4% was established. Most discordance occurred if residual leukaemia was present at levels close to the sensitivity limits. Neither the type of KMT2A fusion nor a new type of treatment hampering MFC methodology had an influence on the concordance rate. The prognostic value of MFC‐MRD and FGT‐MRD differed. MFC‐MRD was able to identify a rapid response at early time‐points, whereas FGT‐MRD was a reliable relapse predictor at later treatment stages. Additionally, the most precise risk definition was obtained when combining the two methods. Because of the high comparability in results, these two rather simple and inexpensive approaches could be good options of high clinical value.
The purpose of this work was evaluation of prognostic significance of 11q23/KMT2A rearrangements in infants (aged under 365 days) with B-cell precursor acute lymphoblastic leukemia (ALL) enrolled in Russian-Belarus multicenter trial MLLBaby. This study is supported by the Independent Ethics Committee and approved by the Academic Council of the Research Institute of Medical Cell Technologies (Ekaterinburg). Various 11q23/KMT2A rearrangements were revealed in 100 (72%) of 139 patients. Event-free survival (EFS) in the intermediate risk group of MLL-Baby trial was 35.1% (standard error (SE) 6.9%), in the high risk group – 38.3% (SE 7.1%) (p = 0.941). The most unfavorable prognosis had infants with translocation t(9;11)/KMT2A-MLLT3: EFS 18.8% (SE 9.8%), cumulative incidence of relapse (CIR) 75.0% (SE 9.7%). Intermediate results were obtained in patients with translocations t(4;11)/KMT2A-AFF1 and t(11;19)/KMT2A-MLLT1: EFS 36.9% (SE 7,2%) and 32,7% (SE 10.4%), respectively; CIR 46.3% (SE 7.8%) and 50.9% (SE 12.3%). The most favorable treatment outcome was achieved in infants carrying translocation t(10;11)(p12;q23)/KMT2A-MLLT10: EFS 83.3% (SE 15.2%), CIR 0,0%. In the multivariate analysis unfavorable outcome of KMT2A-rearranged infant ALL was associated with initial CNS involvement (p = 0.020), initial white blood cell count higher than 300 × 109 /L (p = 0.028), more than 5% blast cells on day 15 in bone marrow (p = 0.012) and presence of translocation t(11;19)/KMT2A-MLLT1 (p = 0.012).
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