Clofarabine in Treating Patients With T-Cell or Natural Killer-Cell Non-Hodgkin’s Lymphoma That Has Relapsed or Not Responded to Previous Treatment

RATIONALE: Drugs used in chemotherapy, such as clofarabine, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing.
PURPOSE: This phase I/II trial is studying the side effects and best dose of clofarabine and to see how well it works in treating patients with T-cell or natural killer-cell lymphoma that has relapsed or not responded to previous treatment.