Design of Southwest Oncology Group Protocol S0016. (A) Schema for patients randomly assigned to six cycles of cyclophosphamide, doxorubicin, vincristine, prednisone chemotherapy with six doses of rituximab (CHOP-R). (B) Schema for patients randomly assigned to six cycles of cyclophosphamide, doxorubicin, vincristine, prednisone chemotherapy followed by consolidation with tositumomab/131I-tositumomab radioimmunotherapy (CHOP-RIT). IV, intravenous.