Iodine I 131 Tositumomab, Etoposide and Cyclophosphamide Followed by Autologous Stem Cell Transplant in Treating Patients With Relapsed or Refractory Non-Hodgkin's Lymphoma

Inclusion Criteria: Patients must have a histologically confirmed diagnosis of lymphoma expressing the cluster of differentiation (CD)20 antigen and generally must have failed at least one prior standard systemic therapy; the exception will be mantle cell lymphoma (MCL) patients, who may be enrolled while in first complete remission (CR) in accordance with current transplant standard of care for these patients Note: Patients with clinically non-transformed follicular lymphomas do not require repeat biopsies for immunophenotyping since these tumors are uniformly reactive with the tositumomab antibody Patients must have tumor burdens < 500cc by computed tomography (CT) or magnetic resonance (MRI) volumetric measurements and must not have splenomegaly at the time of enrollment; splenomegaly will be defined as a spleen volume > 2 standard deviations of the mean spleen volume to body weight ratio (mean = 3.84 cc/kg, SD = 1.53 cc/kg); thus, patients with > 6.9cc/kg will be defined as having splenomegaly; patients with splenomegaly that is thought to be due to G CSF/GM-CSF effect and not due to lymphomatous involvement of the spleen can been deemed eligible with the approval of an investigator Patients must have normal renal function (creatinine [Cr] < 2.0) Patients must have normal hepatic function (bilirubin < 1.5mg/dL), with the exception of patients thought to have Gilbert's syndrome, who may have a total bilirubin above 1.5mg/dL All patients eligible for therapeutic study must have autologous hematopoietic stem cells (2 x 10^6 CD34+ cells/kg) harvested and cryopreserved Patients must have an expected survival of > 60 days and must be free of major infection Exclusion Criteria: Circulating anti-mouse antibody (HAMA) Systemic anti-lymphoma therapy given within 30 days prior to anticipated treatment date Inability to understand or give an informed consent Prior radiation > 20 Gy to any critical normal organ (e.g., lung, liver, spinal cord, or over 25% of red marrow) Central nervous system lymphoma Other serious medical conditions considered to represent contraindications to autologous stem cell transplant (ASCT) (e.g., active coronary artery disease, pulmonary dysfunction [forced expiratory volume in 1 second (FEV1) < 70% expected, Vital Capacity < 70% expected, diffusing capacity of the lung for carbon monoxide (DLCO) < 50%, patient on supplemental oxygen], AIDS, etc.) Pregnancy Prior bone marrow or stem cell transplant Presence of circulating lymphoma cells by morphology or flow cytometry (>= 0.1%) at or near the time of peripheral blood stem cell (PBSC) collection if unpurged PBSC are to be used Southwest Oncology Group (SWOG) performance status >= 2.0 Unable to perform self-care during radiation isolation Patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma/well differentiated lymphocytic lymphoma (ineligible because these tumors express very low surface densities of CD20)