Bexxar has shown efficacy in patients who have failed Rituxan
1385] Rituximab Treatment Failures: Tositumomab and Iodine I 131 Tositumomab [Bexxar®] Can Produce Meaningful Durable Responses.
Sandra J. Horning, Anas Younes, Jennifer Lucas, Donald Podoloff, Vinay Jain. Division of Hematology/Oncology, Stanford University Medical Center, Palo Alto, CA, USA; Division of Hematology/Oncology, MD Anderson Cancer Center, Houston, TX, USA; US Oncology, Dallas, TX, USA
Introduction: Rituximab, a chimeric monoclonal antibody [Mab] directed against CD20 is used extensively for the treatment of patients with indolent non-Hodgkin's lymphoma, producing a response rate of approximately 50%. However, response duration is limited and the vast majority of patients require further treatment. Tositumomab is a murine Mab that also binds CD20 on the surface of normal and malignant CD20 positive lymphocytes with high affinity and specificity. Bexxar is the combination of the unlabeled MAb with the MAb radiolabeled with iodine I 131. Study design: Between July 1998 and November 1999, 40 patients (pts) who had no objective response to rituximab [N=24], progressive disease within 6 months following rituximab [N=12], or progressive disease > 6 months following rituximab [N=4] received radioimmunotherapy with Bexxar on a phase II, multi-center protocol. Patient specific dosing was employed as previously described [J Clin Oncol 19: 3918, 2001]. Eligible pts had indolent (follicular small cleaved or mixed cell, small lymphocytic), transformed indolent or de novo follicular large cell lymphoma. All responses were assessed by an independent, blinded panel. The median follow-up at the time of last blinded assessment was 25.6 [1.2-40] months. Demographics: The median age was 57 years [range 35-78]. The median time from diagnosis to study entry was 50 months [range 11-170]. The median number of prior regimens was 4 [range 1-11]. Results: An overall confirmed response was achieved in 68% of pts, with a median duration of response of 14.7 months [95% CI:10.6-NR]. A complete response (CR), using protocol defined criteria, was achieved in 30% of pts; the median duration of CR has not been reached [95% CI: 11.0-NR] The median time to progression [TTP] for all pts was 12.2 months [5.7-NR]. Fourteen of 40 [35%] patients had a durable response [TTP 12 months]. Nine pts (22.5%) remained in CR at last analysis, with follow-up ranging from 12- 26 months. Conclusion: Bexxar radioimmunotherapy is highly effective in pts with indolent and transformed lymphoma progressive after rituximab. A significant subset of pts experience durable responses and even heavily pretreated pts may sustain prolonged CR.
Keywords: Radioimmunotherapy\ Bexxar\ Non-Hodgkin's lymphoma |
