Yttrium-90-labeled ibritumomab tiuxetan for primary CNS lymphoma

Abstract

11512 Background: Salvage treatment has not yet been established in primary CNS lymphoma (PCNSL). Here we report first results of an ongoing phase II study with a single treatment course of Y-90 anti-CD20 antibody ibritumomab tiuxetan in relapsed/resistant PCNSL. Methods: Eligibility criteria include histologically confirmed, recurrent PCNSL after at least one prior treatment, HIV negativity and adequate bone marrow and cardiac function. Primary endpoint is overall response, secondary endpoints are response duration, survival, and toxicity including late neurotoxicity. Treatment includes rituximab 250 mg/m2 on day -7 and day 0, followed by Y-90-ibritumomab tiuxetan 15 MBq/kg IV. Response evaluation by contrast-enhanced magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (FDG-PET) is scheduled before, one month and two months after treatment as well as every three months thereafter in responders. In two patients single photon emission computed tomography (SPECT) target imaging with gamma-emitting 111-Indium-ibritumomab tiuxetan was performed repeatedly. Results: To date, four patients have been enrolled. Complete response on MRI and decreased but still detectable FDG-uptake in PET was seen in one patient; the response duration was one month. In another patient uncertain complete response with minimal residual contrast enhancement lasting 12+ months was observed. Two patients had disease progression. One patient developed CTC grade 3 pneumonia during CTC grade 2 leukopenia, two patients had CTC grade 3 thrombocytopenia lasting up to 6 weeks. SPECT indicated target accumulation in the tumor starting 48 hours and still ongoing 7 days after injection of 111-Indium-ibritumomab tiuxetan. Conclusions: This is the first report on a successful treatment of PCNSL with Y-90-ibritumomab tiuxetan and penetration of a therapeutic antibody into PCNSL, warranting further investigation. No significant financial relationships to disclose.