Colorectal cancer imaging with iodine-123-labeled CEA monoclonal antibody fragments.

This prospective, randomized multicenter study in 62 patients was designed to evaluate the efficacy and safety of radioimmunodetection (RAID) with 123I-labeled fragments, F(ab')2 and Fab', of IMMU-4, an anti-CEA monoclonal antibody (Immu-RAID-CEA). It was found that ImmuRAID-CEA was safe and disclosed colorectal cancer sites at least 1 cm in size. The positive predictive value by lesions was 77% initially, and increased to 91% after 7 mo of follow-up. Only one patient developed a low level of HAMA. In 17 patients with 32 surgically confirmed lesions, there were 9% true-positive lesions for CT when RAID was false-negative, and 22% for RAID when CT was false-negative. Either CT or RAID detected all 32 lesions. In this small series, therefore, RAID was shown to complement CT findings by confirming suspected tumors and disclosing new lesions which had previously been occult.