title: Use of second antibody in radioimmunotherapy.
abstract: In this study, a second antibody was directed against the first antitumor antibody to accelerate clearance of the 131I-labeled first antibody and improve tumor to normal tissue ratios of radioactivity. The value of this method in improving the therapeutic index of radioimmunotherapy with 131I-antibody to CEA has been investigated in nude mice bearing xenografts of human colon carcinoma and in 5 patients with colorectal cancer. The xenografts did not become saturated with anti-CEA as the administered dose was increased to therapeutic levels. At these high dose levels, the second antibody increased tumor to blood ratios to a maximum of 155:1, 48 times the level in controls that did not receive the second antibody. In 5 patients given 50 mCi of anti-CEA, there was no significant toxicity with the second antibody; clearance of radioactivity was accelerated; and tumor imaging was enhanced. The second antibody appears to have the potential to improve the therapeutic index of radioimmunotherapy.
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000627:therapeutic use*; D000912:Antibodies, Neoplasm / Q000627:therapeutic use*; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D003110:Colonic Neoplasms / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000097:blood / Q000627:therapeutic use / Q000652:urine; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011878:Radiotherapy / Q000379:methods; D012004:Rectal Neoplasms / Q000532:radiotherapy*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000912:Antibodies, Neoplasm; D002272:Carcinoembryonic Antigen; D007457:Iodine Radioisotopes