506U78 in Treating Patients With Relapsed or Refractory T-cell Acute Lymphoblastic Leukemia or T-cell Lymphoblastic Lymphoma

DISEASE CHARACTERISTICS: Histologically confirmed relapsed or refractory T-cell acute lymphoblastic leukemia or T-cell lymphoblastic lymphoma Tumor cells should exhibit phenotypic characteristics of these diseases No CNS involvement requiring intrathecal or craniospinal radiotherapy Must not be eligible for Intergroup, Cooperative Group, or local research studies of higher priority PATIENT CHARACTERISTICS: Age: 16 and over Performance status: ECOG 0-3 OR Karnofsky 40-100% Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Bilirubin no greater than 2.0 mg/dL Renal: Creatinine no greater than 1.5 mg/dL OR Creatinine clearance at least 50 mL/min Other: No neuropathy grade 2 or higher No history of significant neurological toxicity (grade 2 or greater) associated with prior chemotherapy or radiotherapy No active seizure disorder No active infection No other active concurrent malignancy except curatively treated basal cell carcinoma or carcinoma in situ of the cervix Not pregnant or nursing Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: Prior bone marrow transplantation allowed No concurrent allogeneic bone marrow transplantation Chemotherapy: At least 3 weeks since prior chemotherapy (6 weeks for nitrosourea or mitomycin) and recovered No prior 506U78 Endocrine therapy: No concurrent systemic steroid therapy Radiotherapy: See Disease Characteristics Prior radiotherapy allowed Surgery: Not specified Other: No other concurrent investigational therapy No concurrent treatment for seizures