Iodine-131 Anti-B1 Antibody (Tositumomab and Iodine I 131 Tositumomab) for Previously Untreated, Advanced-stage, Low Grade Non-Hodgkin's Lymphoma

This is a single-arm, single-institution, phase II study of Iodine-131 Anti-B1 Antibody for patients with previously untreated, advanced-stage (stage III or IV) low-grade non-Hodgkin's B-cell lymphoma. A total of 75-80 patients will be enrolled. Patients will undergo two phases of the study. In the first phase, termed the "dosimetric dose", patients will receive an infusion of unlabeled Anti-B1 Antibody (450 mg) over 70 minutes (including a 10-minute flush) immediately followed by a 30-minute infusion (including a 10-minute flush) of Anti-B1 Antibody (35 mg) which has been trace-labeled with 5 mCi of Iodine-131. Whole body gamma camera scans will be obtained 5 to 8 times between Days 0 and 7 following the dosimetric dose. Using the dosimetric data from 3 imaging timepoints (the imaging timepoints to be used in decreasing order of preference depending on availability of data are Days 0, 3, and 7; Days 0, 4, and 7; Days 0, 3 and 6; Days 0, 4, and 6; Days 0, 2, and 7; and Days 0, 2, and 6), a patient-specific dose of Iodine- 131 to deliver the desired total body dose of radiotherapy will be calculated. In the second phase, termed the "therapeutic dose", patients will receive a 70-minute infusion (including a 10-minute flush) of unlabeled Anti-B1 Antibody (450 mg) immediately followed by a 30-minute infusion (including a 10-minute flush) of Anti-B1 Antibody (35 mg) labeled with the patient-specific dose of Iodine-131 to deliver a whole body dose of 75 cGy. Patients who are obese will be dosed based upon 137% of their calculated lean body mass. Patients will be treated with either saturated solution potassium iodide (SSKI), Lugol's solution, or potassium iodide tablets starting at least 24 hours prior to the first infusion of the Iodine-131 Anti-B1 Antibody (i.e., dosimetric dose) and continuing for 14 days following the last infusion of Iodine-131 Anti-B1 Antibody (i.e., therapeutic dose). The primary endpoint of the study is the determination of the response rate wit