Intensified induction chemotherapy with high dose cytarabine and etoposide for acute myeloid leukemia: a review and updated results of the Australian Leukemia Study Group.

Induction therapy of acute myeloid leukemia (AML) with standard dose chemotherapy will result in approximately 55-75% of patients achieving a complete remission (CR). Intensification of induction treatment with etoposide and high dose cytarabine does not alter the CR rate but appears to significantly improve the subsequent outcome. Updated results of the comparison of high dose cytarabine with daunorubicin and etoposide in induction (HIDAC-3-7) versus a standard dose combination (7-3-7) demonstrated a highly significant increase in relapse free survival, (RFS) on the high dose arm (p = 0.007) with RFS of 48% at 5 years with HIDAC-3-7 and 25% on 7-3-7. The high dose arm had a more modest survival advantage at 5 years of 33% compared with 25% on standard treatment, possibly because of a higher initial death rate with HIDAC-3-7. The improvement seen in patients with CR after high dose induction appear to parallel results obtained with post-remission therapies intensified with high dose cytarabine. These studies provide clinical evidence that a dose-response effect is present for cytarabine in AML. Intensified treatment is more toxic, gives more profound myelosuppression post-remission and has been shown to benefit younger patients only. Issues of patient selection and the optimal placement of intensification in the treatment sequence require further study. In the future, it is likely that remission duration may be a useful clinical tool to study the influence of new induction therapies on residual resistant leukemia.