Imaging of colon carcinoma with 111-indium-labeled anti-CEA monoclonal antibodies (Indacea) prior to surgery.

Patients with primary and/or metastatic colorectal cancer who had been scheduled for operative intervention were injected intravenously with 200 micrograms of a high-affinity anti-carcinoembryonic antigen (CEA) monoclonal antibody labeled with 2 mCi of 111-indium (Indacea). Patients were imaged by gamma camera at 24 and 48 hours. Primary tumors were identified in 3/10 cases and were not visualized in 3/10 cases. Four scans were considered equivocal. Hepatic metastases were identified as image defects in 5/13 cases and were not visualized in 8/13 cases. All tumors contained CEA by immunoperoxidase staining. In all cases, the primary tumor uptake (5.44 +/- 1.07% ID/kg) was much higher than the uptake of the adjacent fat (0.18 +/- 0.04% ID/kg). There was a direct correlation between tumor CEA content, tumor radioactivity, and the imaging of primary tumor by Indacea. High liver uptake (30.3 +/- 3.0% ID/kg), seen when scanning all patients, was the main limitation of imaging and led to photopenic visualization of hepatic metastases. These results suggest that selection of patients with colorectal carcinoma on the basis of tumor CEA content will lead to improved rates of tumor imaging by Indacea in post-surgical scanning.