Radioimmunotherapy of patients with cutaneous T-cell lymphoma using an Iodine-131-labeled monoclonal antibody: Analysis of retreatment following plasmapheresis

Radioimmunotherapy retreatment of patients receiving radiolabeled murine monoclonal antibodies is difficult because of the human antimurine antibody (HAMA) formation. Retreatment therapy was initiated in three patients at the time of disease progression using a radioiodinated monoclonal antibody (T101). The clinical protocol consisted of a two day plasma exchange (4-6 L) to reduce HAMA titers. Immunoimaging was performed with 5 mCi ¹³¹I-T101 (10 mg). Gamma scintillation images were obtained 18 hr postinfusion, and radiation dosimetry estimates were performed. At 24 hr postinfusion, each patient received a 100-mCi ¹³¹I-T101 (10 mg) therapy dose. Results obtained after plasmapheresis showed a significant reduction, ranging from 28%-61%, in HAMA titers. Blood clearances were markedly different between initial therapy and retreatment therapy for patient with high HAMA titres, reflecting immuno complex formation. Two patients responded to retreatment therapy with responses lasting 1 to 2 mo. Minimal acute and no chronic toxicities were observed during the retreatment protocol.