Patients receive rituximab intravenously (IV) on day 1. Within 7 to 9 days, patients receive rituximab IV and yttrium Y 90 ibritumomab tiuxetan IV in the absence of disease progression or unacceptable toxicity. Distribution and dose absorbed dose will be assessed on day 11. Quality of life will be assessed at screening, at day 1, 36, 92, and at each follow-up visit.