Study of Bexxar <Tositumomab> Combined With External Beam Radiation Therapy

Tositumomab is a CD20-directed radiotherapeutic (131-iodine) monoclonal antibody indicated for the treatment of patients with CD20-positive, relapsed or refractory, low-grade, follicular, or transformed non-Hodgkin's lymphoma who have progressed during or after rituximab therapy, including patients with rituximab-refractory non-Hodgkin's lymphoma. Tositumomab (standard regimen) will be administered at whole body exposure of 75 cGy.

Patient-specific XRT will begin within 24 hours of administration of the therapeutic dose of tositumomab. Subjects will receive local XRT to bulky sites of disease measuring at least 5 cm in at least one dimension. The size and number of fields to be treated will determined by the investigators, but will encompass the patient's most symptomatic/threatening site(s) of disease and not cumulatively include more than 25% of the active bone marrow. Subjects will be treated with the 2 x 2 Gy regimen (2 daily fractions of 2 Gy). Sites of disease previously-irradiated with 30 to 40 Gy will not be treated on this study.

"Potassium iodide (KI) will be administered as:~* Saturated solution potassium iodide (SSKI) 4 drops orally 3-times-a-day,~* Lugol's solution 20 drops orally 3-times-a-day, OR~* KI tablets 130 mg orally once per day KI treatment will start at least 24 hours prior to tositumomab, and continue daily for 14 days following the last dose of tositumomab"