Monoclonal Antibody Therapy

Radioimmunotherapy for Lowgrade Non-Hodgkins Lymphoma

There are two radiopharmaceuticals currently approved in the United States for the nonmyeloablative treatment of recurrent or refractory NHL. Active research is ongoing to investigate other applications for NHL.

Y-90 ibritumomab tiuxetan (Zevalin).

Ibritumomab is a monoclonal antibody directed against the CD20 antigen, which is expressed on normal Blymphocytes and most malignant Blymphocytes in patients with B-cell non- Hodgkins lymphoma. A diagnostic scan with In-111 ibritumomab tiuxetan is performed prior to therapeutic administration for biodistribution. Dose is based on body weight and platelet count. Moderate to severe neutropenia or thrombocytopenia is the principal adverse effect from therapy but is usually self-limited. Y-90 is a pure beta-emitter that allows treatment on an outpatient basis since the radiation risk to others is minimal.

I-131 tositumomab (Bexxar)

Tositumomab is a murine monoclonal antibody that binds to the CD20 antigen expressed on the surface of malignant Blymphocytes. Multiple images are obtained and used to assess biodistribution and to calculate whole body dosimetry for the individual patients. The most common toxicity is reversible myelosuppression. Since radioidine-related hypothyroidism is a potential complication, thyroid blockage prior to dose administration is required.