A Randomized Study of Iodine-131 Anti-b1 Antibody Versus Anti-b1 Antibody in Chemotherapy-relapsed/Refractory Low-grade or Transformed Low-grade Non-Hodgkin's Lymphoma (NHL)

Subjects were randomized to receive either tositumomab (Anti-B1 Antibody) and iodine I 131 tositumomab (Arm A) or unlabeled tositumomab (Arm B). Subjects randomized to Arm B were allowed to cross over and receive I 131 tositumomab once their disease had progressed as long as they still fulfilled the protocol entry criteria (except for exclusion criterion 12, prior monoclonal antibody therapy) and were human anti-murine antibody (HAMA) negative. Study endpoint assessments of response were conducted by a Masked Independent Randomized Radiographic and Oncologic Review (MIRROR) panel and the Study Investigators' assessments of safety and survival. Subjects who completed at least two years of follow-up in Protocol BEX104515 (formerly Corixa Protocol RIT-II-002) were enrolled in long term follow-up Protocol BEX104526 (formerly Corixa Protocol CCBX001-051), an administrative protocol, for continued radiographic response evaluations and safety evaluations every 6 months for years 3 through 5 post-treatment and annually for years 6 through 10 post-treatment. Subjects in BEX104526 were assessed for survival, disease status, subsequent therapy for NHL, and long-term safety, including the use of thyroid medication, development of hypothyroidism, human anti murine antibody (HAMA), myelodysplastic syndrome, acute myelogenous leukemia, and all other secondary malignancies. Additionally, subjects were followed for the development of any adverse event(s) deemed by the Principal Investigator as being possibly or probably related to a subject's previous treatment with Iodine I-131 tositumomab. Laboratory evaluations consisting of a thyroid stimulating hormone level and a complete blood cell count, with a differential and platelet count, were obtained annually through year 10 post-treatment. Dosimetric Dose: Subjects received 450 mg of tositumomab IV followed by 5.0 mCi of Iodine I-131 and 35 mg of tositumomab. Following the dosimetric dose, whole body dosimetry was performed on each subject using a total body gamma camera. Whole body anterior and posterior whole body images were obtained at the following timepoints. 1. Within one hour of infusion of the dosimetric dose and prior to urination 2. 2-4 days after infusion of the dosimetric dose, following urination 3. 6-7 days after infusion of the dosimetric dose, following urination Therapeutic Dose: The total body residence time, derived from total body gamma camera counts obtained at the 3 time points, was used to calculate the iodine-131 activity (mCi) to be administered to deliver the therapeutic total body irradiation dose of 65 or 75 cGy. The therapeutic step was administered 7-14 days after the dosimetric step and consisted of tositumomab 450 mg followed by an activity (mCi) of iodine-131 calculated to deliver 75 cGy or 65 cGy of total body irradiation, depending on platelet count, and 35 mg of tositumomab. For subjects with ≥150,000 platelets/mm3, the recommended dose was the activity of iodine-131 calculated to deliver 75 cGy of total body irradiation; for subjects with NCI Grade 1 thrombocytopenia (platelet counts ≥100,000 but <150,000 platelets/mm3), the recommended dose was the activity of iodine-131 calculated to deliver 65 cGy of total body irradiation.