RATIONALE: Drugs used in chemotherapy use different ways to stop cancer cells from dividing so they stop growing or die. Radiation therapy uses high-energy x-rays to damage cancer cells. Umbilical cord blood transplantation may allow doctors to give higher doses of chemotherapy or radiation therapy and kill more cancer cells.

PURPOSE: Phase II trial to study the effectiveness of chemotherapy, radiation therapy, and umbilical cord blood transplantation in treating patients with hematologic cancer.

OBJECTIVES: I. Determine the safety, efficacy, and toxicity of using cord blood as a source for stem cell transplantation in patients with hematologic malignancies.

OUTLINE: Patients undergo autologous bone marrow harvesting or peripheral stem cell collection prior to transplant regimen, unless the patient has acute leukemia in relapse, aplastic anemia, or myelodysplastic syndrome. Arm I: Patients eligible to undergo total body irradiation (TBI) first receive cyclophosphamide IV over 2 hours on days -5 and -4, then undergo TBI twice a day on days -3 to -1. Patients also receive antithymocyte globulin (ATG) IV over 10 hours on days -3 to -1. Cord blood is infused on day 0. Arm II: Patients not eligible to receive TBI receive oral busulfan every 6 hours on days -7 to -4 for a total of 16 doses. Cyclophosphamide, ATG, and cord blood are then administered as in arm I. All patients receive cyclosporine on days -2 to 180, methylprednisolone on days 5-180, and filgrastim (G-CSF) from day 1. Patients are followed weekly until day 180 and then monthly for 2 years.

PROJECTED ACCRUAL: A total of 20 patients (10 patients per arm) will be accrued for this study within 4 years.

• Graft Versus Host Disease
• Leukemia
• Lymphoma
• Multiple Myeloma and Plasma Cell Neoplasm
• Myelodysplastic Syndromes

• Biological: anti-thymocyte globulin
• Biological: filgrastim
• Drug: busulfan
• Drug: cyclophosphamide
• Drug: cyclosporine
• Drug: methylprednisolone
• Procedure: bone marrow ablation with stem cell support
• Procedure: umbilical cord blood transplantation
• Radiation: radiation therapy

DISEASE CHARACTERISTICS: Histologically proven hematologic malignancy Acute lymphocytic leukemia (ALL): In second or later remission In first remission with poor prognostic features (Philadelphia chromosome positive) Acute myeloid leukemia (AML): In second or later remission In first remission with poor prognostic features, e.g., Arising from myelodysplastic syndrome Cytogenetics with -5, -7, +8, 11q23 abnormalities Complex cytogenetics AML or ALL refractory to induction or in relapse Myelodysplastic syndrome Chronic myelogenous leukemia Severe aplastic anemia or Fanconi's anemia Relapsed Hodgkin's disease Relapsed non-Hodgkin's lymphoma Multiple myeloma No suitable family donor matched for 5 or 6 HLA antigens (A, B, DR) No suitable unrelated donor matched for 6 HLA antigens Cord blood donor available matched for 4-6 out of 6 HLA antigens

PATIENT CHARACTERISTICS: Age: 5 to 50 Performance status: Karnofsky 70-100% Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Bilirubin less than 3 times normal Alkaline phosphatase less than 3 times normal SGOT less than 3 times normal Renal: Creatinine less than 2 times normal OR Creatinine clearance greater than 60 mL/min Cardiovascular: MUGA with ejection fraction at least 50% Pulmonary: DLCO and spirometry at least 60% OR Exercise VO2 max/kg at least 15 mL/min/kg Other: HIV antibody negative Hepatitis B surface antigen negative No active bacterial, viral, or fungal infection

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: Not specified Radiotherapy: Prior radiotherapy allowed If following limits have not been exceeded, patient may receive total body irradiation: No prior radiation to one entire kidney Whole liver received no greater than 1000 cGy No prior whole abdomen radiotherapy Small bowel received no greater than 3000 cGy Heart received no greater than 1800 cGy No prior whole lung radiotherapy CNS received less than 30 cGy (whole brain or any portion of the spine) Surgery: Not specified