Abstract
Polymerase chain reaction (PCR) -based minimal residual disease (MRD) quantification on childhood acute lymphoblastic leukemia (ALL) is performed with immunoglobulin (Ig) /T-cell receptor (TCR) gene rearrangements by amplification of the clone-specific sequences of the junctional regions of the monoclonal rearrangements. This method has been developed and standardized in Europe, and become essential to large-sized multicenter clinical trials. As several studies have elucidated a strong correlation between the MRD levels at an early stage of therapy and clinical outcome on various cases, many trials have incorporated the stratification according to the amount of MRD. In Japan we have detected gene rearrangements of TCRγ, TCRδ, Igκ and IgH with multiplex PCR and heteroduplex analysis and measured MRD levels by nested PCR in the Chldren's Cancer and Leukemia Study Group (CCLSG). Consequently we have conducted protocols with PCR-MRD-based stratification founded on the data from our retrospective study of MRD quantification. However our technique of detection of rearrangements and MRD quantification is not satisfactory, compared with the standard method of European countries. We are now trying to introduce these current methods such as real-time quantitative PCR (RQ-PCR) to achieve high enough quality to fulfill the global standard of PCR-based MRD quantification.
