Safety and Efficacy of Zevalin in the Treatment of Non-Hodgkin's Lymphoma

Summary of major inclusion and exclusion criteria. Other Safety criteria will need to be met. Inclusion Criteria: * Histologically confirmed, relapsed or refractory CD20+ follicular B-cell NHL within 12 months of Study Day 1 (without clinical evidence of transformation). NHL must require treatment as determined by an increase in overall tumor size. The presence of B symptoms, and/or the presence of masses which are causing ongoing clinical symptoms. * Bidimensionally measurable disease meeting the minimum requirement of at least 1 lesion \>/= 2.0 cm in a single dimension. * No lymphoma therapy for 3 weeks prior to Study Day 1. * Patients must be recovered from all toxicities associated with prior surgery, radiation therapy, chemotherapy, or immunotherapy. * Signed IRB-approved informed consent. * Greater than 18 years of age. * Expected survival \>/= 3 months. * WHO performance status of \</= 2. * Acceptable hematologic status, liver function, renal function, and pulmonary function. * Female patients who are not pregnant or lactating. * Men and women of reproductive potential who are following accepted birth control methods. Exclusion Criteria: * Patients with impaired bone marrow reserve, which may be indicated by prior myeloablative therapy with autologous bone marrow transplantation (ABMT) or peripheral blood stem cell (PBSC) rescue. * Prior radioimmunotherapy, including the Zevalin regimen. * Prior immunotherapy, including Rituxan therapy within 6 months of Study Day 1. * Rituxan-refractory (no response to most recent Rituxan-containing regimen, or TTP was \< 6 months). * Presence of CNS lymphoma. * Patients with chronic lymphocytic leukemia (CLL). * Known history of HIV or AIDS. * Serious nonmalignant disease or infection * Major surgery, other than diagnostic surgery, within 4 weeks of Study Day 1. * Patients who received investigational product within 4 weeks of Study Day 1 or patients who may experience long-term toxicity from a previous investigational therapy.