Rituximab, Cyclophosphamide, and G-CSF Followed By Combination Chemotherapy in Treating Patients Who Are Undergoing Autologous Stem Cell Transplant Followed By Rituximab and GM-CSF for Refractory Diffuse Large B-Cell Lymphoma

OBJECTIVES: * Determine the disease-free and overall survival of patients with refractory diffuse large B-cell lymphoma treated with stem cell mobilization comprising rituximab, cyclophosphamide, and filgrastim (G-CSF) followed by high-dose chemotherapy comprising carmustine, etoposide, and cyclophosphamide and autologous peripheral blood stem cell transplantation, rituximab, and sargramostim (GM-CSF). * Determine any potential infectious complications in patients treated with this regimen. * Determine the effect of GM-CSF on antibody-dependent cellular cytotoxicity in patients treated with this regimen. OUTLINE: Stem cell mobilization: Patients receive rituximab IV over 4-8 hours on days 1, 5, 8, and 13. Patients also receive cyclophosphamide IV over 1-2 hours on day 9 and filgrastim (G-CSF) subcutaneously (SC) once daily beginning on day 10 and continuing until an adequate number of peripheral blood stem cells (PBSC) are collected. High-dose preparative regimen: Patients receive carmustine IV over 2 hours on day -6, etoposide IV over 4 hours on day -4, and cyclophosphamide IV over 2 hours on day -2. Autologous PBSC transplantation: Patients undergo autologous PBSC transplantation on day 0. Patients receive sargramostim (GM-CSF) SC once daily beginning on day 6 and continuing until blood counts recover. Post-transplant regimen: Patients receive GM-CSF SC once daily on days 42-73, 177-208, 362-393, 543-574, and 727-758. Patients also receive rituximab IV over 4-8 hours on days 45, 52, 59, 66, 180,187, 194, 201, 365, 372, 379, 386, 546, 553, 560, 567, 730, 737, 744, and 751. After completion of study treatment, patients are followed periodically for 10 years. PROJECTED ACCRUAL: A total of 44 patients will be accrued for this study.