- Monoclonal antibody therapy: Beginning 3-6 weeks after the completion of radiotherapy, patients receive rituximab IV followed by indium In 111 ibritumomab tiuxetan IV over 10 minutes on day 1. Patients then undergo whole body imaging. If ibritumomab tiuxetan biodistribution is acceptable, patients receive rituximab IV and yttrium Y 90 ibritumomab tiuxetan IV over 10 minutes on day 7, 8, OR 9.