Localization of intraperitoneal xenografts of human colon cancer by radiolabeled anti-CEA antibodies.

An intraperitoneal xenograft tumor model was developed in the nude mouse to represent advanced colorectal disease in the human patient. Intraperitoneal (ip) and subcutaneous (sc) tumor xenografts were successfully localized by indium 111-labeled anti-carcinoembryonic antigen monoclonal antibodies (Indacea) administered intravenously (IV) or in-traperitoneally (IP). In the sc model, tumor uptake (% injected dose per g of tumor tissue—%lD/g) was significantly improved at 72 hours postin-jection when Indacea was administered IP (44.01 ± 1.94 vs. 33.74 ± 0.87, P<0.005). In the ip model, tumor uptake at 72 hours was improved with IP Indacea (28.23 ± 5.42 vs. 19.36 ± 5.50, P<0.01) and the tumor to blood ratio was significantly improved for IP Indacea (17.83 ± 2.95 vs. 8.45 ± 1.38, P<0.01). Tumor mass was not a contributing factor in these differences. This study demonstrates that ip xenografts can be successfully imaged using radiolabeled antibodies and that the IP route of administration results in better tumor uptake of the antibody in ip lesions.