OUTLINE: This is a dose-escalation, multicenter study. If myelosuppression is found to be the dose-limiting toxicity, patients are stratified according to prior therapy (more than 2 multiagent chemotherapy regimens or radiotherapy to more than 20% of the bone marrow or stem cell transplantation with or without total body irradiation vs more than 2 single-agent phase I or phase II agents) and extent of disease (bone marrow involvement vs meeting none of the stratum I criteria).