In order to confirm our initial report on the negative impact of MDR1
gene expression on the outcome of de novo acute myeloid leukemia (AML)
, we present an update of our prospective study with a larger number o
f patients and a longer duration of follow-up. At diagnosis, MDR1 RNA
expression of the leukemic cells was negative in 37% and positive in 6
3% of the patients (N = 79). The complete remission rate of induction
chemotherapy was 76% for MDR1 RNA negative and 54% for MDR1 RNA positi
ve patients (p = 0.05). At a median observation duration of 33 months,
the duration of overall survival was 19 months for the MDR1 RNA negat
ive patients but only 8 months for the patients with MDR1 gene express
ion (p = 0.02). Thus the long-term data also indicate that MDR1 gene e
xpression is an unfavourable prognostic factor in AML.