Page 91 - 2019_02-Haematologica-web

Deep sequencing method for MRD monitoring in AML
AB
CD
Figure 4. Analysis of overall survival and disease-free survival in patients with acute myeloid leukemia stratified according to minimal residual disease levels deter- mined by conventional methods. Kaplan-Meier plots of (A) overall survival and (B) disease-free survival according to minimal residual disease (MRD) assessment by multiparametric flow cytometry (MRC) and (C) overall survival and (D) disease-free survival according to MRD assessment by quantitative polymerase chain reac- tion (qPCR) analysis. The numbers of censored patients with respect to each stratified group and numbers at risk are indicated. Statistically significant values: *P<0.05, **P<0.01.
usually associated with monocytic subtype-AML, which frequently presents more difficulties for identifying MRD by MFC. Indeed, Salipante et al.27 described that the level of success of MFC depends greatly on the immunophenotype of the abnormal blasts and how to discriminate them from background regenerative blasts. Moreover, due to the lack of standardization, MFC shows substantial variability across laboratories, including that of sample processing, instrument configuration, number of events, and training of pathologists.32 The lack of a strong correlation between NGS and qPCR could be explained by the nature of the sample (sequencing uses gDNA whereas qPCR uses cDNA). Although RNA overexpression allows a higher sensitivity of detection, RNA levels do not correlate with the number of tumor cells, in contrast to mutated DNA.
Accordingly, mutated DNA is more representative of the tumor burden than is overexpression of mutated RNA.35 It should be noted that the prediction of survival and progres- sion of AML using MRD NGS was better than that of the other methodologies employed, at least in the cohorts evaluated.
Finally, survival analysis showed that MRD positive sta- tus determined by NGS was associated with a higher risk of relapse and death and that MRD negative status in post- consolidation ssmples was associated with longer overall and disease-free survival, in accordance with recently pub- lished studies.23 Supporting these findings, previous studies reported that an MRD check-point after consolidation could be the best moment for analysis because it afforded better prediction.8,34-37 Cox regression multivariate analyses
haematologica | 2019; 104(2)
295