Imaging of human colorectal adenocarcinoma with indium-labeled anticarcinoembryonic antigen monoclonal antibody.

Twenty patients with 21 primary colorectal adenocarcinomas were studied with 2 mCl (7.6 X 10(7) becquerels) of indium-labeled monoclonal antibody (200 micrograms) specific for carcinoembryonic antigen (CEA). Fifteen lesions (71%) were visualized by gamma camera scintigraphy at 48 hours postinjection. Tumors that were identified by immunoscintigraphy were large (38.10 +/- 17.76 cm3 vs 6.00 +/- 1.65 cm3), had a grossly fungating component, had a high content of CEA by enzyme immunoassay (12.9 +/- 3.6 micrograms/g vs 3.3 +/- 1.7 micrograms/g), and had an apical and/or intraluminal staining pattern on immunohistologic section. Patients whose tumors were visualized had a low serum CEA level (1.9 +/- 0.4 ng/mL vs 14.6 +/- 8.0 ng/mL). Prospective selection of patients for follow-up imaging or therapy with radiolabeled monoclonal antibodies may be feasible using these measurements.