Patients undergo bone marrow biopsy at baseline and prior to courses 3, 6, and 8 for evaluation of treatment response. Bone marrow samples are analyzed for myeloblast phenotypic expression profiles, which include the following parameters: percentage of CD34-positive myeloblasts; antigen expression density of CD13, CD34, CD45, and CD117; and aberrant myeloblast expression of CD4, CD11c, CD15, and CD56.