- Arm I (R-CHOP-21): Patients receive R-CHOP immunochemotherapy comprising rituximab IV, cyclophosphamide IV over 15 minutes, doxorubicin IV, and vincristine 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.