Phase II Study of Yttrium-90-Ibritumomab Tiuxetan in Patients With Relapsed or Refractory Mantle Cell Lymphoma

Purpose This phase II trial evaluated the safety and efficacy of yttrium-90 (Y-90)-ibritumomab tiuxetan in patients with relapsed or refractory mantle cell lymphoma (MCL). Patients and Methods Patients with relapsed or refractory MCL were eligible for the study if they had adequate major organ function and performance status. Those with CNS disease, pleural effusion, circulating lymphoma cells >= 5,000/mu L, or history of stem-cell transplant were ineligible. Patients with a platelet count >= 150,000/mu L received a dose of 0.4 mCi/kg of Y-90-ibritumomab tiuxetan, whereas those with a platelet count less than 150,000/mu L received a dose of 0.3 mCi/kg. Results Thirty-four patients with a median age of 68 years (range, 52 to 79 years) received the therapeutic dose. The patients had received a median of three prior treatment regimens (range, one to six treatment regimens), including those that contained rituximab (n = 32) and bortezomib (n = 7). Of the 32 patients with measurable disease, 10 (31%) achieved complete or partial remission. After a median follow-up of 22 months (range, 2 to 72+ months), an intent-to-treat analysis revealed a median event-free survival (EFS) duration of 6 months and an overall survival duration of 21 months. The median EFS for those who achieved partial or complete remission was 28 months, while it was 3 months for those whose disease did not respond (P < .0001); it was 9 months for patients whose tumor measured less than 5 cm in the largest diameter before treatment and 3 months for those whose tumor measured >= 5 cm (P = .015). Conclusion The single-agent activity of 90Y-ibritumomab tiuxetan and its favorable safety profile warrant its further development for the treatment of MCL.