Participants in this study have diffuse large B-cell lymphoma (DLBCL) or follicular lymphoma and must be at least 60 years old. Participants must also have received standard chemotherapy and their PET scans must show they had a complete response after chemotherapy.
This study is being done to see how well the study drug called Zevalin (ibritumomab tiuxetan) works and if it is safe to give. The study will compare the effects of the study drug with observation (no further therapy). Observation is standard care for cancer that is in complete remission. About 490 subjects with DLBCL from 80 sites worldwide will take part in this study.