Long-term responses in patients with recurring or refractory B-cell non-Hodgkin lymphoma treated with yttrium 90 ibritumomab tiuxetan

BACKGROUND. Radioimmunotherapy with radiolabeled monoclonal antibodies to CD20 produces a high response rate in patients with recurring non-Hodgkin lymphoma (NHL), but the durability of those remissions is not well defined. METHODS. Data on patients with recurring NHL treated with yttrium Y 90 ibritumomab tiuxetan in 4 clinical trials were reviewed to identify patients with a long-term response, defined as a time to progression of 12 months or longer. RESULTS. Long-term responses were seen in 37% (78/211) of patients. At a median follow-up of 53.5 months (range, 12.7-88.9) the median duration of response was 28.1 months and the median time to progression was 29.3 months. A third of these patients had been treated with at least 3 previous therapies, and 37% of them had not responded to their last therapy. The findings in patients with follicular lymphoma (n = 59) were similar to those in the overall population of long-term responders. The estimated overall survival at 5 years was 53% for all patients treated with ⁹⁰Y ibritumomab tiuxetan and 81% for long-term responders. CONCLUSIONS. A single dose of ⁹⁰Y ibritumomab tiuxetan can produce durable responses and prolonged overall survival in a substantial number of patients in whom previous therapies have failed.