Presurgical imaging with indium-labeled anti-carcinoembryonic antigen for colon cancer staging

Over a 4-year period, 108 patients with known or suspected colorectal cancer were studied by radioimmunoconjugate scintigraphy prior to operative procedures. Study subjects received 0.2 to 40 mg i.v. of murine anti-carcinoembryonic antigen monoclonal antibody labeled with 2-5 mCi of 111In (Indacea). Resected tissues were analyzed for 111In and carcinoembryonic antigen content. Tumor, liver, and draining lymph nodes had over 10% injected dose/kg compared to less than 2.5% injected dose/kg for other normal tissues. Primary tumors that were successfully imaged were significantly larger and had higher 111In and carcinoembryonic antigen content. In 54 patients, primary tumors were visualized with a sensitivity of 78%. Hepatic metastases (58 patients) were visualized as negative filling defects (sensitivity, 45%). Extrahepatic (intraabdominal) metastases (25 patients) were visualized (sensitivity, 48%) as areas of increased uptake. Extraabdominal metastases were uncommon (10 patients; sensitivity, 80%). Of 56 patients with known or suspected hepatic metastases who presented with no evidence of extrahepatic disease by conventional tests (X-ray, computerized tomographic scan), 20 (36%) were documented to have extrahepatic metastases at exploratory surgery and 10 of these (50%) had the extrahepatic disease localized by the Indacea scan. The management of these 10 patients was, or could have been, modified by the scan findings and unnecessary surgery eliminated.