<qa>  What is the name of the treatment that patients receive on day 1?- Chemotherapy: Patients receive rituximab IV over 2-5 hours, cyclophosphamide IV, doxorubicin IV, and vincristine IV on day 1; oral prednisone on days 1-5 or 2-6; and filgrastim G-CSF subcutaneously SC on days 7-15. Patients also receive darbepoetin alfa SC on day 1. Treatment repeats every 21 days for up to 6 courses in the absence of disease progression or unacceptable toxicity. 