A combination of monoclonal antibodies used to treat certain types of non-Hodgkin lymphoma. The monoclonal antibody tositumomab is given with iodine I 131 tositumomab (a form of tositumomab that has been chemically changed by adding radioactive iodine). Monoclonal antibodies are made in the laboratory and can locate and bind to substances in the body, including cancer cells. Also called iodine I 131 tositumomab, tositumomab, and tositumomab and iodine I 131 tositumomab.