Patients receive rituximab IV, cyclophosphamide IV, doxorubicin hydrochloride IV, and vincristine IV on day 1 and oral prednisone on days 1-5. Treatment repeats every 14 days for up to 6 courses in the absence of disease progression or unacceptable toxicity. Rituximab IV alone is continued for an additional 2 courses after completion of the initial 6 courses.