Factors associated with toxicity and response to yttrium 90-labeled ibritumomab tiuxetan in patients with indolent non-Hodgkin's lymphoma

Treatment of patients with indolent non-Hodgkin's lymphoma (NHL) is evolving. These patients usually present with advanced-stage disease. Treatment options for patients who experience relapse are limited, and no treatment has been shown to be superior to others in improving overall survival of this group of patients, with the possible exception of allogeneic stem cell transplantation. Therefore, new approaches are needed to improve outcomes in patients with relapsed or refractory disease. The anti-CD20 monoclonal antibody, rituximab, was the first monoclonal antibody approved for the treatment of indolent B-cell NHL. As a single agent in the treatment of relapsed or refractory indolent lymphoma, response rates as high as 56% have been observed. This promising new therapy was followed by development of radioimmunotherapy, a novel treatment approach that combines the targeting capability of monoclonal antibodies with the additional cytotoxic effects of radiation. Yttrium 90-labeled ibritumomab tiuxetan (Zevalin®) is a radiolabeled monoclonal antibody that has been shown to produce clinically significant responses in up to 80% of patients with indolent NHL and is the first radiolabeled monoclonal antibody approved for therapeutic use in the treatment of lymphoma. This article reviews some of the safety and efficacy data for this agent in addition to examining factors that could aid in predicting response and toxicity in patients with low-grade relapsed or refractory NHL treated with ⁹⁰Y ibritumomab tiuxetan.