Comparison between qualitative and real-time polymerase chain reaction to evaluate minimal residual disease in children with acute lymphoblastic leukemia

Abstract

IntroductionMinimal residual disease is an important independent prognostic factor that can identify poor responders among patients with acute lymphoblastic leukemia.ObjectiveThe aim of this study was to analyze minimal residual disease using immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements by conventional polymerase chain reaction followed by homo-heteroduplex analysis and to compare this with real-time polymerase chain reaction at the end of the induction period in children with acute lymphoblastic leukemia.MethodsSeventy-four patients diagnosed with acute lymphoblastic leukemia were enrolled. Minimal residual disease was evaluated by qualitative polymerase chain reaction in 57 and by both tests in 44. The Kaplan–Meier and multivariate Cox methods and the log-rank test were used for statistical analysis.ResultsNine patients (15.8%) were positive for minimal residual disease by qualitative polymerase chain reaction and 11 (25%) by real-time polymerase chain reaction considering a cut-off point of 1 × 10−3 for precursor B-cell acute lymphoblastic leukemia and 1 × 10−2 for T-cell acute lymphoblastic leukemia. Using the qualitative method, the 3.5-year leukemia-free survival was significantly higher in children negative for minimal residual disease compared to those with positive results (84.1% ± 5.6% versus 41.7% ± 17.3%, respectively; p-value = 0.004). There was no significant association between leukemia-free survival and minimal residual disease by real-time polymerase chain reaction. Minimal residual disease by qualitative polymerase chain reaction was the only variable significantly correlated to leukemia-free survival.ConclusionGiven the difficulties in the implementation of minimal residual disease monitoring by real-time polymerase chain reaction in most treatment centers in Brazil, the qualitative polymerase chain reaction strategy may be a cost-effective alternative.

Current Strategies for the Detection of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia

“…Alternatively, some authors have proposed the detection of Ig/TCR rearrangements by conventional PCR using consensus primers and homo/heteroduplex analysis, despite its lower analytical sensitivity, considering that this approach allows identification of patients with greater residual tumor burden, and then at high risk of relapse. 22 , 27 , 49 , 50 , 78 , 79 , 87 , 88 …”

“…Therefore, rearrangements of the immunoglobulin heavy chain gene (IgH), light chain kappa (IgK), TCR delta (TCRD), TCR gamma (TCRG), TCR beta (TCRB) and light chain lambda (IgL) may be detected at different frequencies in ALL of B and T-cell lineages. 11 , 17 , 19 , 35 , 37 , 41 , 62 , 68 , 72 – 79 …”

“…Although it does not identify residual leukemic cells in proportions lower than 10 −3 , it allows the identification of patients with greater residual tumor burdens and those at high risk of relapse, and can be considered a cost-effective methodology for MRD monitoring in countries with limited financial resources. 27 , 79 A qualitative MRD result (presence or absence) provides limited information and does not allow for an evaluation of tumor kinetics, making it impossible to correlate the final amount of PCR product and the initial amount of target molecules. 11 …”

Qualitative polymerase chain reaction versus quantitative polymerase chain reaction for the detection of minimal residual disease in children with acute lymphoblastic leukemia

“…In this issue of the Revista Brazileira de Hematology e Hemoterapy, Paula et al 15 compared MRD monitoring using Ig and TCR gene rearrangements by conventional PCR followed by homo-heteroduplex analysis with clone-specific probes to RQ-PCR at the end of induction in 44 children with ALL. According to RQ-PCR MRD cut-off points established by the GBTLI-2009 protocol, the agreement between the two methods was 40% for B lineage ALL and 100% for T-cell ALL.…”