This phase II trial is studying how well giving iodine I 131 tositumomab together with etoposide and cyclophosphamide followed by autologous stem cell transplant works in treating patients with relapsed or refractory non-Hodgkin's lymphoma. Radiolabeled monoclonal antibodies, such as iodine I 131 tositumomab, can find cancer cells and deliver radioactive cancer-killing substances to them without harming normal cells. Drugs used in chemotherapy, such as etoposide and cyclophosphamide, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Combining a radiolabeled monoclonal antibody with combination chemotherapy before autologous stem cell transplant may kill more cancer cells