A Randomized Phase III Study to Compare Arsenic Trioxide (ATO) Combined to ATRA and Idarubicin Versus Standard ATRA and Anthracyclines-based Chemotherapy (AIDA Regimen) for Patients With Newly Diagnosed, High-risk Acute Promyelocytic Leukemia - ICH GCP - Clinical Trials Registry 10 GPt/l) comparing standard AIDA-based treatment with ATO/ATRA combination including low-doses idarubicin during induction. The investigators propose a modified ATO/ATRA protocol with the addition of two doses of IDA (50% compared to standard AIDA induction) for induction because of the anticipated need of adding anthracyclines to control hyperleukocytosis and to achieve long-term disease control in this high-risk APL population. This is followed by 4 cycles of ATO/ATRA consolidation therapy. As in the APL0406 study for low/intermediate-risk patients the investigators expect less severe hematologic toxicity and treatment-related mortality resulting in an improved outcome for patients in the experimental arm. Furthermore, from the start of consolidation, these patients (in contrast to the standard arm) can be treated on an outpatient basis, which is also considered to be associated with an improved quality of life. The study will be conducted as a European intergroup study. " />