Thomas A Davis, Abstract Co-Author: Nothing to Disclose

Mark S Kaminski, Abstract Co-Author: Nothing to Disclose

John P Leonard, Abstract Co-Author: Nothing to Disclose

Richard Leo Wahl MD, Presenter: Nothing to Disclose

Stewart Kroll, Abstract Co-Author: Nothing to Disclose

Morton Coleman, Abstract Co-Author: Nothing to Disclose

Michael Goris, Abstract Co-Author: Nothing to Disclose

Andrew Zelenetz, Abstract Co-Author: Nothing to Disclose

Ronald Levy, Abstract Co-Author: Nothing to Disclose

Susan Knox, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

To assess the contribution of I¹³¹ conjugation to Tositumomab, a CD20 antibody, by comparing therapeutic outcomes following Tositumomab and I¹³¹ Tositumomab (the BEXXAR® therapeutic regimen) with those following an equivalent dose of unlabeled Tositumomab.

Pts with refractory or relapsed LG NHL were randomized to receive BEXXAR therapy or unlabeled Tositumomab. Eligible pts with subsequent progression after unlabeled Tositumomab treatment could crossover to receive BEXXAR therapy.

In all, 78 pts were randomized to receive BEXXAR therapy (n=42) or unlabeled Tositumomab (n=36). Median number of prior therapies was 2 (range, 1-5), and median follow-up was 42.6 mo (range, 1.9-71.5 mo). Responses to BEXXAR therapy vs unlabeled Tositumomab were: OR 55% vs 19% (P=.002); CR 33% vs 8% (P=.012); median OR duration 14.7 mo (95% CI: 7.4-NR) vs 28.1 mo (95% CI: 7.6-NR); median CR duration NR vs 43.8 mo (95% CI: 28.1-NR); and median TTP 6.3 vs 5.5 mo (P=.035), respectively. Of the pts who had a CR after BEXXAR therapy, 71% (10/14) remained in CR for 29.8+ to 71.1+ mo. Two pts who responded after unlabeled Tositumomab have ongoing responses at 48.1+ to 56.9+ mo. Nineteen pts received BEXXAR crossover therapy. Responses to BEXXAR crossover therapy vs unlabeled Tositumomab were: CR 42% vs 0% (P=.008); OR 68% vs 16% (P=.002); median OR duration 12.6 vs 7.6 mo (P=.001); and median TTP 12.4 vs 5.5 mo (P=.01), respectively. Hematologic toxicity was more prominent after BEXXAR therapy; grade 4 neutropenia, anemia and thrombocytopenia (platelets <25,000/mm³) were 17%, 5%, and 12% after BEXXAR therapy; 37%, 0%, and 26% after BEXXAR crossover therapy; and 3%, 0%, and 0% after Tositumomab alone, respectively. The incidence of nonhematologic adverse events was similar between the 2 arms with the exception of nausea, which occurred more frequently after BEXXAR therapy.

Although changes in dose or schedule might optimize the effect of unlabeled Tositumomab, an equivalent dose of the radioimmunoconjugate appeared to provide a superior therapeutic effect.

R.L.W.,T.A.D.,M.S.K.,J.P.L.,M.C.,A.Z.,S.K.: Authors receive research support from GlaxoSmithKline and Corixa. Additionally, all authors are on speaker bureau and receive honorariaS.K.: Corixa employee

Davis, T, Kaminski, M, Leonard, J, Wahl, R, Kroll, S, Coleman, M, Goris, M, Zelenetz, A, Levy, R, Knox, S, et al, , Randomized Trial Assessing the Contribution of Iodine 131 (I¹³¹) Conjugation to Tositumomab Compared with Tositumomab Alone in Patients (Pts) with Relapsed or Refractory Low-Grade (LG) or Transformed LG non-Hodgkin’s Lymphoma (NHL).  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4414709.html