Radioimmunotherapy: a new treatment modality for B-cell non-Hodgkin's lymphoma

The field of radioimmunotherapy for the treatment of non-Hodgkin's lymphoma (NHL) has advanced significantly over the past decade, and several radioimmunoconjugates are being tested in clinical trials. Two of these antibodies target CD20: yttrium-90 (Y-90)-labeled ibritumomab tiuxetan (Zevalin) and tositumomab/iodine-131 (I-131)-labeled tositumomab (Bexxar). Other agents target either CD22 (Y-90 epratuzumab) or human leukocyte antigen (HLA)-DR (I-131 Lym-1), respectively. In February 2002, Y-90-labeled ibritumomab tiuxetan became the first radioimmunoconjugate to be approved by the US Food and Drug Administration (FDA) for the treatment of cancer. Tositumomab/I-131 tositumomab was approved in June 2003. Thus, two radioimmunoconjugates have been approved for the treatment of NHL. Both agents, when administered as a single dose, have produced impressive tumor response rates with an acceptable toxicity profile. The main side effect is reversible myelosuppression. Radioimmunotherapy produces overall response rates of approximately 80% in patients with low-grade lymphomas, and 25% to 30% of patients achieve a complete remission. Lower response rates (approximately 40%) have been reported in patients with large-cell lymphomas. This review discusses the clinical trials of radioimmunotherapeutic agents for NHL that demonstrated their safety and efficacy and outlines the current status of these agents.