Study to Treat Relapsed Follicular Non-Hodgkin's Lymphoma With Radiation and Bexxar

"Patients will be treated in two dosing phases, each phase includes two infusions. The first phase, termed dosimetric dose, involves an intravenous administration of 450 mg unlabeled tositumomab followed by an intravenous administration of 5 mCi (0.18 GBq) of I-131 tositumomab for the purpose of determining the rate of whole body clearance of radioactivity (residence time) so that the administered activity (mCi or GBq) to deliver a 75 cGy (or 65 cGy for patients with baseline platelet count from 100,000 to 149,999/mm\^3) total body radiation dose can be calculated."

All patients are to receive 20 Gy in 10 fractions of 200 cGy to the PTV