PURPOSE (1) Quantification of minimal residual disease (MRD) by competitive CBFbeta/MYH11 reverse-transcriptase polymerase chain reaction (RT-PCR) in patients with acute myeloid leukemia (AML) and inversion(16) [inv(16)] during postremission therapy, (2) comparison of this method with conventional two-step RT-PCR, and (3) evaluation of a potential prognostic value. PATIENTS AND METHODS MRD of six consecutive adult patients with AML and inv(16)(p13;q22) or t(16;16)(p13;q22) who entered complete remission (CR) was monitored by competitive CBFbeta/MYH11 RT-PCR in their bone marrow (BM) during postremission therapy with high-dose cytarabine (HiDAC) or after BM transplantation with a matched unrelated-donor marrow (MUD-BMT) during an observation period of 4.5 to 27 months after initiation of treatment. RESULTS Competitive PCR showed a gradual decline by at least 4 orders of magnitude after 7 to 9 months in patients in continuous CR (CCR), while one patient who relapsed after 13.5 months only achieved a reduction by 2 orders of magnitude at the end of consolidation therapy. A rapid decrease below the detection limit was observed within 1 month in two patients after MUD-BMT. A temporary reappearance of molecular MRD was observed in these patients during immunosuppression for graft-versus-host disease (GvHD). After reduction of immunosuppression, the level of MRD dropped again below the PCR detection limit. Molecular monitoring by conventional two-step RT-PCR yielded comparable results only when multiple assays per time point were performed, while single-assay RT-PCR gave misleading results. CONCLUSION Competitive RT-PCR is a valuable tool for molecular monitoring during postremission chemotherapy, as well as after BMT.
Low frequency of reverse transcription polymerase chain reaction-detectable chromosome aberrations in relapsed acute myeloid leukaemia: implications for detection of minimal residual disease