Bexxar®: Novel Radioimmunotherapy for the Treatment of Low‐Grade and Transformed Low‐Grade Non‐Hodgkin's Lymphoma

Learning Objectives After completing this course, the reader will be able to: Describe advances in clinical radioimmunotherapy. Discuss ongoing translational research in radioimmunotherapy. Identify future directions for radioimmunotherapy in cancer medicine. Access and take the CME test online and receive one hour of AMA PRA category 1 credit at http://CME.TheOncologist.com Purpose. Immunotherapy using monoclonal antibodies to specifically target B cells has provided new hope to many patients with indolent lymphomas, particularly those with chemotherapy‐refractory disease. Lymphomas are extremely sensitive to radiation, and significant progress has been made over the last decade in the development of radioimmunotherapy with anti‐CD20 antibodies. Materials and Methods. Herein we review clinical experience with tositumomab and iodine I 131 tositumomab (Bexxar®; Corixa Corporation; South San Francisco, CA; and GlaxoSmithKline; Philadelphia, PA) in patients with non‐Hodgkin's lymphoma. Results. Therapy with Bexxar has demonstrated high response rates and long durations of response compared with unconjugated anti‐CD20 antibodies in patients with relapsed low‐grade and transformed low‐grade non‐Hodgkin's lymphomas. Iodine‐131 (I‐131) has a long history of clinical experience, an excellent safety record, and favorable nuclear and pharmacologic properties. Importantly, the gamma emissions of iodine‐131 facilitate accurate dosimetry to calculate the appropriate patient‐specific therapeutic activity to deliver a predetermined total‐body dose of radiation, thereby minimizing hematologic toxicity. In clinical trials of Bexxar, objective response rates ranged from 54%–71% in heavily pretreated patients. In the pivotal trial, the number of patients with a longer duration of response after treatment with Bexxar was significantly greater than the number of patients with a longer duration of response after their last qualifying chemotherapy regimen. In 76 newly diagnosed patients, the objective response rate was 97%, and 63% of patients achieved complete responses. Conclusion. These data suggest that Bexxar will become an important new option in the treatment of indolent lymphoma.