S0801 Iodine I 131 Tositumomab, Rituximab, and Combination Chemotherapy in Previously Untreated Stage II, Stage III, or Stage IV Follicular Non-Hodgkin Lymphoma

OBJECTIVES: * To evaluate the response rate in patients with previously untreated stage II-IV follicular non-Hodgkin lymphoma treated with rituximab, cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone (R-CHOP) in combination with iodine I 131 tositumomab. * To evaluate the toxicity of this regimen in these patients. * To estimate the 3-year progression-free survival rate in patients treated with this regimen. * To estimate the 5-year progression-free and overall survival rate in patients treated with this regimen. * To assess the safety profile of this regimen in these patients. OUTLINE: This is a multicenter study. * Induction therapy: Patients receive R-CHOP\* comprising rituximab IV, cyclophosphamide IV, doxorubicin hydrochloride IV, and vincristine sulfate IV on day 1 and oral prednisone once daily on days 1-5. Treatment repeats every 21 days for up to 6 courses in the absence of disease progression or unacceptable toxicity. Patients with at least stable disease then proceed to consolidation therapy. NOTE: \*Patients receive R-CHOP in courses 1-4 and CHOP alone in courses 5 and 6. * Consolidation therapy: Within 12 weeks after completion of induction therapy, patients receive tositumomab IV over 1 hour followed by a dosimetric dose of iodine I 131 tositumomab IV over 20 minutes. Patients then undergo whole body gamma camera scans over a 1-week period to determine the rate of total body clearance of radioactivity and the therapeutic dose of iodine I 131 tositumomab. Within 7-14 days after the dosimetric dose, patients receive tositumomab IV over 1 hour followed by a therapeutic dose of iodine I 131 tositumomab IV over 20 minutes. Patients with at least stable disease then proceed to maintenance therapy. * Maintenance therapy: Beginning approximately 1 year after study entry and no more than 28 days after restaging, patients receive rituximab IV every 3 months for up to 4 years (16 courses) in the absence of disease progression or unacceptable toxicity. After completion of maintenance therapy, patients are followed annually for up to 7 years. Patients who do not complete maintenance therapy are followed every 6 months for 2 years and then annually for up to 7 years.