Zevalin Before Stem Cell Transplant in Treating Patients With Non-Hodgkin Lymphoma

PRIMARY OBJECTIVES: I. To measure the response conversion (progressive disease \[PD\]/stable disease \[SD\] to partial response \[PR\] and complete response \[CR\]). SECONDARY OBJECTIVES: I. To assess the time to engraftment/chimerism. II. To assess the rate of acute and chronic graft-versus-host disease (GVHD). III. To assess toxicity. IV. To determine the overall survival. V. To investigate immune functional and phenotypic analysis. VI. To measure two year event free survival (EFS). OUTLINE: CONDITIONING REGIMEN: Patients receive rituximab intravenously (IV) on days -21 and 14, ibritumomab tiuxetan IV on day -14, TLI on days -11 to -7 and -4 to -1, and antithymocyte globulin IV over 4-6 hours on days -11 to -7. Patients also undergo TLI on days -11 to -7 and -4 to -1. TRANSPLANT: Patients undergo allogeneic peripheral blood stem cell transplant (PBSCT) on day 0. GVHD PROPHYLAXIS: Patients receive cyclosporine orally (PO) twice daily (BID) or IV on days -3 to 56 with taper to 6 months and mycophenolate mofetil PO BID or IV on days 0-28. After completion of study treatment, patients are followed up periodically.