The aim of the study is to test [90]Y-ibritumomab tiuxetan, a radioactive antibody, in patients with stage III or IV follicular lymphoma whose disease is in partial or complete remission after first line chemotherapy. The radioactive antibody will be compared with no further treatment to see which is better in the long term after standard lymphoma treatment.

The study has previously been posted by Schering AG, Germany. Schering AG, Germany has been renamed to Bayer Schering Pharma AG, Germany.

Bayer Schering Pharma AG, Germany is the sponsor of the trial.

Inclusion Criteria:

• Non Hodgkin Lymphoma stage III or IV at timepoint of diagnosis
• Patients who have achieved a remission after first line chemotherapy
• No less than 6 weeks and no more than 12 weeks since last dose of chemotherapy
• older than 18 years
• written informed consent

Exclusion Criteria:

• Any other anticancer treatment for NHL except the preceding first line chemotherapy
• Prior radiation therapy
• Patients who have not recovered from the toxic effects of the first line chemotherapy
• Any other cancer or history of cancer less than 10 years ago
• Patients with known HIV positivity
• patients with pleural effusion or ascites
• female patients who are pregnant or breast feeding (women of childbearing potential must have a negative serum pregnancy test at study entry)
• Adults not employing an effective method of birth control during study treatment and 12 months thereafter
• Patients unable or unwilling to comply with protocol