Dosimetry/Validation Study of 131Iodine-Anti B1 (Murine) Radioimmunotherapy for Chemotherapy Refractory Low Grade B Cell Lymphomas and Low Grade Lymphomas That Have Transformed to Higher Grade Histologies

Patients receive a dosimetric dose consisting of 450 milligrams (mg) of unlabeled tositumomab (TST, Anti-B1 Antibody) intravenously (IV) followed by 5 milliCurie (mCi) of Iodine I 131 TST IV. Serial whole body sodium iodide probe scintillation counts and whole body conjugate view gamma camera scans obtained approximately 1 hour after administration and then daily for the next 7 days were used to determine the radioactive clearance and the dose of iodine I 131 TST required to deliver a 75 centigray (cGy) therapeutic dose. The therapeutic dose was administered 7-14 days after the dosimetric dose and consisted of TST 450 mg and an activity of Iodine 131 calculated to deliver 75 cGy or 65 cGy of total body irradiation, depending on platelet count, and 35 mg TST.