Monitoring minimal residual disease by qualitative detection of immunoglobulin H/T cell receptor γ by using multiplex polymerase chain reaction in children with acute lymphocytic leukemia

Abstract

Objective To explore the prognostic significance in monitoring minimal residual disease (MRD) in childhood acute lymphoblastic leukemia (ALL) by a simple method, and to detect cloned immunoglobulin H (IgH) and T cell receptor γ (TCRγ) gene rearrangements by using multiplex polymerase chain reaction (PCR) and automated fragment analysis. Methods Bone marrow samples were collected from 86 newly diagnosed cases of childhood ALL at the Department of Pediatrics, the First Affiliated Hospital of Sun Yat-Sen University, from May of 2009 to August of 2013.IgH and TCRγ gene rearrangements were amplified by qualitative multiplex PCR.The clonality of PCR production was analyzed by GENEMAPPERID software.Only those carried monoclonal IgH/TCRγ on diagnosis were arranged to monitor MRD.Detectable monoclonal IgH/TCRγ by the end of induction was defined as MRD positive.All patients were treated with GD2008 ALL protocol.Clinical data of all newly-diagnosed ALL patients in the corresponding period were reviewed.The final follow-up on May 31, 2014.Survival rates and event free survival (EFS) curves were estimated by the Kaplan-Meier, and compared by using the log-rank test. Results The percent age of 94.2(81/86 cases) patients was at least 1 marker positive.Subsequent MRD was monitored in 79 cases.The median follow-up time was 20 months (9-61 months). By the end of induction, 20 cases were MRD positive and 59 cases were MRD negative, and the 3-year EFS were 56.4%±14.7% and 94.0%±3.4% (χ2=8.563, P=0.003), respectively.According to the traditional prognostic stratification criteria, MRD was detected 65 cases in the non-high risk group: 23 cases in stan-dard risk group and 42 cases in intermediate risk group, and the difference of 3-year EFS had no statistical significance (95.3%±4.7% vs 76.6%±9.0%, χ2=0.934, P=0.334). While using MRD by the end of induction as a risk stratification criterion, there was a statistical significant difference compared with the 3-year EFS for MRD-negative (n=52) group and MRD-positive (n=13) group(93.1%±3.8% and 59.5%±16.2%, χ2=7.128, P=0.008). Conclusions It is a simple but feasible method to monitor MRD in childhood ALL by using this qualitative multiplex PCR with automated fragment analysis for monoclonal IgH/TCRγ gene rearrangements.MRD by the end of induction can be used as a more accurate risk stratification criterion than the traditional one.It is worth of further research. Key words: Acute lymphoblastic leukemia; Prognosis; Minimal residual disease