Study of radiolabeled indium-111 and yttrium-90 ibritumomab tiuxetan in primary central nervous system lymphoma

BACKGROUND. Therapeutic options for refractory or recurrent primary central nervous system lymphoma (PCNSL) are limited. The blood-brain barrier makes many agents used in systemic lymphomas ineffective in CNS lymphomas. The objective of this study was to determine whether intravenous radioimmunotherapy using anti-CD20 antibody can be delivered to PCNSL. METHODS. This was a single-institution prospective study. Indium-111 ibritumomab tiuxetan was used for imaging and dosimetry. Yttrium-90 ibritumomab tiuxetan at doses of 0.3 to 0.4 mCi/kg were subsequently given for the treatment of recurrent or refractory PCNSL. In-111 data were used to estimate radiation doses to lesions delivered by Y-90 ibritumomab tiuxetan therapy. RESULTS. Six patients (4 men, 2 women) with a median age of 60 years and median Karnofsky performance status of 70 received both indium-111 and yttrium-90 ibritumomab tiuxetan. The median absorbed dose delivered to the CNS lymphoma was 701 cGy compared with 70 cGy to normal brain. The median progression-free and overall survival times were 6.8 weeks and 14.3 weeks, respectively. CONCLUSIONS. The results from this study suggest that it may be feasible to deliver radiolabeled monoclonal anti-CD20 antibodies as a component of therapy for PCNSL.