The quality of molecular response to chemotherapy is predictive for the outcome of AML1-ETO-positive AML and is independent of pretreatment risk factors.

The outcome of 45 AML1-ETO-positive acute myeloid leukemia (AML) patients was analyzed with special emphasis on the quality of molecular response to therapy. Patients received double induction therapy, either 6-thioguanine, cytarabine, and daunorubicin (TAD9)/high-dose cytosine arabinoside plus mitoxantrone (HAM) or HAM/HAM, followed by consolidation therapy (TAD9) according to the AML-Cooperative group 92 trial (AMLCG92) and AML-Cooperative group 99 trial (AMLCG99). All cases underwent cytomorphological, cytogenetical and molecular genetic analyses. AML1-ETO transcript levels were quantitatively assessed at diagnosis and during follow-up by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The median reduction of initial AML1-ETO expression level was 4 log (range 0-5) after both induction and consolidation therapies. The quality of molecular response after induction as well as consolidation therapies had significant impact on the cumulative incidence of relapse (P=0.021 and P=0.001, respectively), event free survival (EFS: P=0.001 and P=0.001, respectively) and overall survival (OS: P=0.013 and P=0.014, respectively). HAM/HAM improved the molecular response to induction therapy (P=0.042) but after consolidation, no differences in molecular response were detectable between TAD9/HAM and HAM/HAM. Patient- or disease-related factors had no impact on the molecular response to induction or consolidation therapy. The current study demonstrates that quantification of AML1-ETO transcript levels is a powerful tool for prediction of prognosis that is independent of pretreatment risk factors, and may be helpful for directing therapeutic decisions in the future.