Introduction: 90Yttrium ibritumomab tiuxetan (Zevalin®) is a drug for radiommunotherapy based on murine IgG monoclonal antibody (MoAb) targeting CD20 antigen. The treatment with 90Y ibritumomab tiuxetan is recommended for patients with relapsed or refractory CD20+ follicular B-cell non-Hodgkin’s lymfoma (NHL). Material and method: Authors performed the first administration of 90Y ibritumomab tiuxetan in March 2004 in 59-years-old man with follicular B-cell NHL, initial stage IVA (abdominal paraaortal lymphonodes + involvement of bone marrow), diagnosed in 1996. Patient underwent CHOP chemotherapy + radiotherapy (36 Gy) and maintainance therapy with interferon-alpha. Six years later the patient relapsed and intraspinal infiltration (Th 5–7) and affection of vertebrae Th 3–10 with paraparesis of lower limbs occurred. Paraparesis regressed after high-dose BEAM chemotherapy with transplantation of peripheral blood stem cells. Back pain appeared again in January 2004, MRI detected tumor infiltration in front of vertebrae Th 7–10, in diameter of 4 cm. The second administration of 90Y ibritumomab tiuxetan was realized in April 2004 in 65- years-old woman with follicular B-cell NHL, initial stage IVB (generalized lymphadenopathy + involvement of right kidney), diagnosed in 2003. The partial remission was induced after 6 cycles of CHOP chemotherapy. There was a small residual tumor in abdomen, supraclavicular nodes and the right kidney involvement. In both patients rituximab (MabThera® – “cold” chimeric MoAb) was administered intravenously at the dose of 250 mg/m2. Next dose of rituximab was administered after 1 week, followed with intravenous infusion of 90Y ibritumomab tiuxetan (the man – 825 MBq – 11 MBq/kg, the dose was reduced for mild thrombocytopenia, the woman 925 MBq – 15 MBq/kg). Continual pump was shielded by plexiglass and dose rate was 120 nSv/hour from 1 meter (m). One hour after injection dose rate in 1 m from patient was 2.5 µSv/hour and 24 hours after injection was 0.95 µSv/hour. Whole-body scintigraphy 24 and 86 hours after injection was performed by means of the bremsstrahlung detection. Results: During 90Y ibritumomab tiuxetan administration no allergic reaction has occurred. In restaging in the man a partial remission with residual involvement of vertebrae Th 10–11 has been achieved, in the woman no tumor residuum was detected.

        Key words: monoclonal antibody – 90Y ibritumomab tiuxetan – non-Hodgkin’s lymfoma – CD20