OUTLINE: This is a dose escalation study. Patients receive a 30 minute intravenous infusion of mitoxantrone once a week on day 1. On days 2-6 of each week, patients receive subcutaneous filgrastim (granulocyte colony-stimulating factor; G-CSF). Treatment continues for patients who respond to therapy and exhibit no disease progression. Dose escalation proceeds until the maximum tolerated dose (MTD) of mitoxantrone with G-CSF support is determined. The MTD is defined as the dose preceding that at which 2 or more patients experience dose limiting toxicity. After the MTD is determined, an additional 20-40 patients are enrolled at this dose level to examine their response to this therapy.