Safety and Efficacy of Radioimmunotherapy with 90Yttrium-rituximab in Patients with Relapsed CD20+ B cell Lymphoma: A Feasibility Study

Purpose: Both anti-CD20 antibodies (ibritumomab; ZEVALIN® and tositumomab; BEXXAR®) currently used for radioimmunotherapy of B cell non-Hodgkin's lymphoma are murine immunoglobulins. The aim of this feasibility study was to evaluate the safety and efficacy of radioimmunotherapy with a human chimeric anti-CD20 antibody labelled with Yttrium-90 ( 90 Y-rituximab) in patients with B cell lymphoma. Methods: Patients with CD20+ B-cell lymphoma in partial remission or with progressive disease after at least one line of therapy were included. 90 Y-rituximab was administered according to a similar schedule as currently approved by the European Medicines Agency for the treatment with 90 Y-ibritumomab tiuxetan (ZEVALIN ® ): a first infusion of rituximab 250 mg/m² is repeated one week later and directly followed by the injection of 90Y-rituximab (14,8 MBq/kg). 18 FDG-PET/CT was performed before treatment and repeated 3 months after for response assessment. Results: Twenty-six patients were treated with 90 Y-rituximab. Disease histologies included mainly follicular lymphomas (53%). Toxicity was primarily haematological. The incidence of grade 3-4 neutropenia, thrombocytopenia and anemia were 34%, 38%, and 8% respectively, with spontaneous recovery in all but one patient that needed autologous stem cell transplant for refractory thrombocytopenia. Among the relevant long-term side effects, one patient developed secondary myelodysplasia 2 years after the treatment. The overall response rate was 88% (95% CI: 70%-98%), including 65% complete metabolic responses and 23% partial metabolic responses. After a median follow-up of 29.6 months, the Kaplan-Meier estimated median progression-free survival was 9.1 months (95% CI 6.1-17.9). Median time to next treatment was 24 months (95% CI: 12.8-28).