ABSTRACT
Recurrent molecular markers have been routinely used in acute myeloid leukemia (AML) for risk assessment at diagnosis, whereas their post-induction monitoring still represents a debated issue. We evaluated the prognostic value and biological impact of minimal residual disease (MRD) and of the allelic ratio (AR) of FLT3-internal-tandem duplication (ITD) in childhood AML. We retrospectively screened 494 children with de novo AML for FLT3-ITD mutation, identifying 54 harboring the mutation; 51% of them presented high ITD-AR at diagnosis and had worse event-free survival (EFS, 19.2 versus 63.5% for low ITD-AR, <0.05). Forty-one percent of children with high levels of MRD after the 1st induction course, measured by a patient-specific real-time-PCR, had worse EFS (22.2 versus 59.4% in low-MRD patients, P<0.05). Next, we correlated these parameters with gene expression, showing that patients with high ITD-AR or persistent MRD had characteristic expression profiles with deregulated genes involved in methylation and acetylation. Moreover, patients with high CyclinA1 expression presented an unfavorable EFS (20.3 versus 51.2% in low CyclinA1 group, P<0.01). Our results suggest that ITD-AR levels and molecular MRD should be considered in planning clinical management of FLT3-ITD patients. Different transcriptional activation of epigenetic and oncogenic profiles may explain variability in outcome among these patients, for whom novel therapeutic approaches are desirable.
Subject(s)
Leukemia, Myeloid, Acute/diagnosis , Leukemia, Myeloid, Acute/genetics , fms-Like Tyrosine Kinase 3/genetics , Child , Child, Preschool , Disease-Free Survival , Epigenesis, Genetic/genetics , Gene Expression Regulation, Leukemic , Humans , Neoplasm, Residual/genetics , Prognosis , Retrospective StudiesABSTRACT
The aim of the study was to analyze the impact of minimal residual disease (MRD) after reinduction therapy on the outcome of children with relapsed 'high-risk' acute lymphoblastic leukemia (ALL). Sixty patients with isolated or combined marrow relapse were studied. All patients belonged to the S3 or S4 groups, as defined by the Berlin-Frankfurt-Münster stratification for relapsed ALL. MRD was studied by real-time quantitative PCR after the first, second and third chemotherapy course (time points 1 (TP1), 2 (TP2) and 3 (TP3), respectively). MRD results, not used for treatment refinement, were categorized as negative (NEG MRD), positive not-quantifiable (POS-NQ MRD) when MRD level was below quantitative range (a level <10(-4)) or positive within quantitative range (POS MRD) when MRD level was >or=10(-4). With a median observation time of 15 months, overall 3-year event-free survival (EFS) was 27%. The 3-year EFS was 73, 45 and 19% for patients with NEG-MRD, POS NQ-MRD and POS-MRD at TP1, respectively (P<0.05). The prognostic predictive value of MRD was statistically confirmed in multivariate analysis. MRD quantitation early and efficiently differentiates patients who benefit from conventional treatment, including allogeneic hematopoietic stem cell transplantation, from those needing innovative, experimental therapies.
