AML1 ETO FUSION MESSENGER-RNA CAN BE DETECTED IN REMISSION BLOOD-SAMPLES OF ALL PATIENTS WITH T(821) ACUTE MYELOID-LEUKEMIA AFTER CHEMOTHERAPY OR AUTOLOGOUS BONE-MARROW TRANSPLANTATION/

The chromosomal translocation t(8;21)(q22;q22) in acute myeloid leukem ia (AML) can be detected by a reverse transcription-polymerase chain r eaction (PT-POP) for the chimeric AML1/ETO transcript. We have evaluat ed the clinical relevance of this method for monitoring and detection of minimal residual disease (MRD) in seven patients who reached a comp lete hematological remission (CHR) after chemotherapy or autologous bo ne marrow transplantation (ABMT). Peripheral blood (PB) samples of fiv e patients in first continuous complete remission (CCR) were still POP -positive at a frequency of 1 in 10(5) cells after 7, 8, 8, 10 or 66 m onths. Chemotherapy led to a reduction from first- to second-step PCR- positivity in three serially monitored patients. AML1/ETO mRNA was als o detected in the PB of two patients in CCR, 10 or 12 months after ABM T. PB and bone marrow (BM) showed identical results in all samples tes ted simultaneously. AML1/ETO fusion transcripts were neither found in the PB and BM of a healthy individual, nor in the PB of a patient afte r allogeneic BMT for cytogenetically proven t(8;21)-leukemia. Our resu lts indicate the presence of cells carrying the AML1/ETO rearrangement in the PB and BM of all patients in CHR after chemotherapy or ABMT fo r t(8;21)-positive AML. While this finding raises interesting question s about the biology of acute leukemia, it limits the value of the AML/ ETO PT-POP for the prediction of impending relapse.