Serial quantification of minimal residual disease of t(8;21) acute myelogenous leukaemia with RT-competitive PCR assay.

The chromosomal translocation (8;21)(q22;q22) in the AML M2 subtype according to the FAB classification, results in the production of a novel fusion gene AML1/ETO. The chimaeric AML1/ETO transcript is useful for the detection of minimal residual disease (MRD). Recently, several studies on the detection of AML1/ETO transcripts in t(8;21) AML have been reported. However, the clinical significance of a small number of AML1/ETO transcripts by a reverse transcription-polymerase chain reaction (RT-PCR) remains to be elucidated. We have developed a novel quantitative RT-competitive PCR assay and evaluated the clinical usefulness of this method by the monitoring of MRD in eight patients with t(8;21) AML. In four patients in first continuous complete remission (CR) the value of MRD was always < 0.1 fg of the competitor dose throughout their courses, whereas in four relapsed patients there was an increase in the value of MRD to > 0.1 fg of the competitor dose before cytogenetic relapse. We conclude that the detection of the presence of cells with AML1/ETO fusion transcripts by our RT-competitive PCR assay may be useful to monitor disease progression and to predict subsequent relapse.