 Patients receive rituximab IV over 3-6 hours, cyclophosphamide IV over 30 minutes, doxorubicin IV over 5 minutes, and vincristine IV over 5 minutes on day 1 and oral prednisone on days 1-5. Treatment repeats every 21 days for 3-8 courses. Patients undergo whole-body positron-emission tomography PET scanning at baseline and after course 3 to determine response. Results from the genetic testing and PET scans are used to determine further treatment recommendations. 