Yttrium-90 ibritumomab tiuxetan as a single agent in patients with pretreated B-cell lymphoma: evaluation of the long-term outcome.

Background: Based on historical data on the role of radioimmunotherapy (RIT) in pretreated non-Hodgkin lymphoma, we reviewed our hospital's clinical database.
Patients and Methods: Between 2005 and 2008, 57 patients previously treated with at least 1 rituximab-containing chemotherapy were treated with Yttrium-90-labeled ibritumomab tiuxetan ((90)Y-IT). The median number of pretreatments was 3 (range, 1-9 pretreatments). A total of 46 patients had stage III/IV disease (31 with bone marrow involvement); 6 had bulky disease. According to histology, 53 were follicular lymphoma (FL), 2 were marginal zone lymphoma, and 2 were small lymphocytic lymphoma.
Results: Overall response rate was 93% (53 of 57); complete response (CR) rate was 70% (40 of 57). Twenty-six of 40 patients (65%) who obtained a CR are in continuous CR (CCR) with a median follow-up of 20 months (range, 10-42 months); 4 of them still maintain their CCR after 36 months. All patients achieving a CCR had FL, and 21 of them with stage III/IV disease; 12 of 26 had been heavily pretreated (>or= 3 previous treatments), and 2 had had autologous stem cell transplantation. Toxicity was primarily hematologic and mostly transient; no grade 4 extrahematologic toxicity was observed.
Conclusion: This study confirms the safety and high efficacy of (90)Y-IT RIT in heavily pretreated FL patients, with the possibility of having a subset of long-term responders.