Chemotherapy Followed by Zevalin for Relapsed Mantle Cell Lymphoma

* Patients receive fludarabine (days 1-3), mitoxantrone (day 1), and rituximab (day 1) of each 28-day cycle. * Patients undergo a CT scan and bone marrow biopsy after two cycles. Unless the cancer has progressed, the patient will then receive Zevalin study treatment. * Blood counts are taken every week for 12 weeks. After 12 weeks, a CT scan and bone marrow biopsy are performed. * Long-term followup is 4 years. Physical exam and blood work is performed every 3 months for the first two years. Following that, physical exams and blood work is every 6 months for another two years. CT scans and bone marrow biopsies are every 6 months during this 4 year followup period.