FLT3 and acute promyelocytic leukemia: Pre-arsenic trioxide (ATO) studies showed reduced OS and increased relapse rates with FLT3-ITD [9,15,21] in APL, whereas post-ATO studies demonstrated no prognostic significance of FLT3-ITD [17,18,19,20], suggesting the effect of FLT3-ITD may be mitigated with ATO.