896 IMAGING NEUROBLASTOMA IN PATIENTS WITH RADIOLABELED MONOCLONAL ANTIBODY AS A BASIS FOR TARGETING THERAPY

Abstract

We have shown in previous studies that iodine 131-labeled monoclonal antibody (Mab) 3F8 could image human neuroblastoma (NB) xenografts in mice with excellent tumor to tissue ratios and could ablate such tumors with minimal toxicities. We now report our human imaging studies as the basis for targeting radiotherapy. Patients with NB were injected iv with 1.5 to 5 mCi iodine 131 labeled Mab 3F8. Serial gamma scannings were done. Tumor localization was apparent by 15 hours. Tissue radioactivity (uCi/cc) was calculated based on orthogonal gamma images. There was no focal uptake in the normal brain, liver, spleen or the adrenal gland. Tumor to nontumor ratios were 10-20:1 between 15 to 140 hours after injection. Sites of uptake were confirmed as tumors at surgery in selected patients. Tumor to tissue ratio was 4-14: 1 for blood, 16-58:1 for liver, 5-19:1 for kidney, 10-36:1 for red marrow, and 540-1940:1 for CSF. In all patients sites of iodine uptake were consistent with tumor by conventional radiological studies. Deiodination with stomach excretion was significant. From tissue decay curves, relative radiation to normal organs were 4-12% (to blood 37%) of the tumor dose. Toxicities included pain and shortness of breath, both being reversible. No hematological side effects were noted. The radiolabeled Mab 3F8 might have clinical potentials for the imaging and therapy of human neuroblastomas.