Preoperative imaging of colorectal carcinoma with 111In-labeled anticarcinoembryonic antigen monoclonal antibody

Patients with primary, recurrent, or metastatic colorectal adenocarcinoma were given injections of 200 micrograms of anticarcinoembryonic antigen (CEA) monoclonal antibody labeled with 2 mCi of 111In (Indacea). Patients were imaged at 24 and 48 h. Celiotomy was performed on 40 patients between 3 and 17 days post-Indacea injection. Of 16 primary tumors, 11 (69%) were imaged. Of six extrahepatic recurrences, none was imaged. Intrahepatic metastases were visualized as negative images in 10 of 24 (42%) patients. On the basis of the activity in tissue expressed as a percentage of the total radioactive dose per kg injected into the patient (% ID/kg), extrahepatic tumors that were imaged using Indacea had a significant uptake of radiolabel in the tumor [5.99 +/- 0.91% ID/kg (SE)] and in the associated normal mesenteric lymph nodes (12.0 +/- 2.4% ID/kg). The CEA content of these tumors was high (13.3 +/- 4.7 micrograms/g), and, histologically, the CEA was located primarily apically or intraluminally. Intrahepatic tumor imaging correlated only with tumor size. The greatest Indacea uptake was seen in normal liver (22.1 +/- 3.2% ID/kg). Low Indacea uptake was seen in fat (0.21 +/- 0.05% ID/kg) and bowel wall (1.11 +/- 0.17% ID/kg). In conclusion, Indacea imaging of colorectal carcinoma is specific for high concentrations of accessible CEA in CEA-bearing tumors or in lymph nodes draining these tumors. The successful clinical use of monoclonal antibodies for tumor imaging and therapy will require careful selection of patients for a number of antigen-related parameters including antigen content and distribution in tumors. This information will only come from careful correlation between image results and tissue analysis. High uptake by normal liver tissue is the major unresolved problem with labeled antibody imaging.