- Radioimmunotherapy: Within 4-7 weeks after the completion of R + CHOP chemotherapy, patients receive rituximab IV and an imaging dose of indium In 111 ibritumomab tiuxetan IV over 10 minutes on day 1. Patients then undergo whole body gamma imaging scans during the first day (2-24 hours) and the second or third day (48-72 hours) after injection. In the absence of altered biodistribution, patients receive rituximab IV followed by yttrium Y 90 ibritumomab tiuxetan (IDEC-Y2B8; yttrium Y 90 Zevalin®) IV over 10 minutes on day 8.