Experimental study of tumor detection using 131I-labeled F (ab)2 fragments of monoclonal antibodies to CA 19-9 and CEA (IMACIS-1)

To determine if IMACIS-1 might have the capability of specifically pinpointing an adenocarcinoma in the human lung, xenografts of adenocarcinomatous nude mice that were injected with IMACIS-1 have been evaluated by scintigraphy, and the IMACIS-1 biodistribution in the tissue measured after sacrifice. Results have revealed that scintigraphic images obtained twenty-four hours after the IMACIS-1 injection showed some activity in the area of the tumor. At seventy-two hours after the IMACIS-1 injection, tumoral radioactivity was only seen in mice with a large tumor. At ninety-two hours after injection, the animals were sacrificed and a biodistribution study was performed. The IMACIS-1 uptake was expressed in counts per minute per gram of tissue. The tissue-to-blood uptake ratio in mice with a large tumor was 8.4 in the viable part of the tumor, 27.2 in the necrotic part of the tumor, 3.0 in the liver, and 1.5 in the spleen, respectively. In contrast, the ratio in mice with a small tumor was 3.4 in the viable part and 18.3 in the necrotic part. Immunoperoxidase staining with either the anti CEA or the anti CA 19-9 antibody was strongly visible in the necrotic part of the tumor.