DETECTION EFFICIENCY OF COLORECTAL-CARCINOMA RECURRENCE USING TECHNETIUM-PERTECHNETATE ANTI-CARCINOEMBRYONIC ANTIGEN MONOCLONAL-ANTIBODY BW-431 26/

Background. A new anti-carcinoembryonic antigen (CEA) antibody, BW 431 /26 (Scintimun, Behring-Werke, Marburg, Germany), labeled with technet ium pertechnetate (Tc-99m), is an intact immunoglobulin G(1) monoclona l antibody that has been used to image colorectal cancer (CRC). This r eport is part of a prospective multicenter clinical trial initiated by the International Atomic Energy Agency to evaluate the role of this a ntibody in radioimmunoimaging of patients with suspected disease recur rence. Methods. A group of 31 consecutive patients underwent radioimmu noimaging with Tc-99m-BW 431/26 after resection of their primary CRC. Patient referral was based on either a persistent rise in serum CEA le vels of unknown origin and/or questionable findings by other imaging s tudies. Whole-body planar scans and single photon emission computed to mography scans of selected body regions (e.g., chest, abdomen) were pe rformed up to 24 hours after the intravenous antibody injection. Patho logic antibody concentration localizations by radioimmunoimaging were correlated with surgical, clinical, and other imaging modality finding s to validate the accuracy of radioimmunoimaging in detecting CRC recu rrence. Results. A total of 75 detected tumoral lesions was evaluated: 26 of 75 were of known origin (36%), and 49 of 75 were of unknown ori gin (65%). There were four true-negative lesions, one false-negative l esion, and no false-positive lesions; all others were true-positive le sions. Sensitivity was 96.8%, specificity 100%, and accuracy 98.6%. Th e study was easy to perform, without untoward side effects on patients after antibody administration. Conclusions. Anti-CEA antibody radioim munoimaging is a highly reliable diagnostic procedure in detecting CRC recurrence and is useful especially for the diagnosis of patients wit h rising CEA blood levels of unknown origin, thereby significantly aff ecting patient management. Radioimmunoimaging should become part of th e diagnostic workup of patients suspected of having CRC recurrence.