- Radioimmunotherapy: Between 4-6 weeks after completion of ESHAP chemotherapy, patients receive rituximab IV followed by indium In 111 ibritumomab tiuxetan IV over 10 minutes on day 1. Patients with < 25% bone marrow involvement and expected biodistribution proceed to treatment. Patients receive rituximab IV followed by yttrium Y 90 ibritumomab tiuxetan IV over 10 minutes on day 7, 8, or 9.