Radioimmunotherapy with iodine I-131 tositumomab for relapsed or refractory B-cell non-Hodgkin lymphoma: updated results and long-term follow-up of the University of Michigan experience

CD20-targeted radioimmunotherapy is a promising new treatment for B-cell no n-Hodgkin lymphoma (NHL), We now provide updated and long-term data on 59 c hemotherapy-relapsed/refractory patients treated with iodine I-131 tositumo mab in a phase VII single-center study. Fifty-three patients received indiv idualized therapeutic doses, delivering a specified total-body radiation do se (TBD) based on the clearance rate of a preceding dosimetric dose. Six pa tients received dosimetric doses only, Dose-escalations of TBD were conduct ed separately in patients who had or had not undergone a prior autologous s tem cell transplant (ASCT) until a nonmyeloablative maximally tolerated TBD was established (non-ASCT = 75 cGy, post-ASCT = 45 cGy), Fourteen addition al non-ASCT patients were treated with 75 coy. Unlabeled antibody was given prior to labeled dosimetric and therapeutic doses to improve biodistributi on. Forty-two (71%) of 59 patients responded; 20 (34%) had complete respons es (CR). Thirty-five (83%) of 42 with low grade or transformed NHL responde d versus 7 (41%) of 17 with de novo intermediate-grade NHL (P=.005). For al l 42 responders, the median progression-free survival was 12 months, 20.3 f or those with CR, Seven patients remain in CR 3 to 5.7 years, Sixteen patie nts were re-treated after progression; 9 responded and 5 had a CR, Reversib le hematologic toxicity was dose limiting, Only 10 patients (17%) had human anti-mouse antibodies detected. Long-term, 5 patients developed elevated t hyroid-stimulating hormone levels, 5 were diagnosed with myelodysplasia and 3 with solid tumors. A single, well tolerated treatment with iodine I-131 tositumomab can, therefore, produce frequent and durable responses in NHL, especially low-grade or transformed NHL, (Blood, 2000;96:1259-1266) (C) 200 0 by The American Society of Hematology.