COMPARISON OF RADIOIMMUNODETECTION WITH OTHER IMAGING METHODS IN EVALUATING LOCAL RELAPSES OF COLORECTAL-CARCINOMA

Background. The prognosis for colorectal cancer patients is related cl osely to the extent of tumor at the time of diagnosis, and early detec tion of metastatic or recurrent disease is an important prerequisite f or successful treatment. Radioimmunodetection is a relatively new tech nique to image colorectal cancer using radiolabelled monoclonal antibo dies (MoAb). The goal of this study was to evaluate the clinical use o f radioimmunodetection with the anticarcinoembryonic antigen MoAb FO23 C5, radiolabelled with I-131, in patients submitted to surgery for col orectal cancer and with suspected local recurrences. The results of ra dioimmunodetection were compared with those of computed tomography, ul trasonography, magnetic resonance imaging, and other diagnostic techni ques (gastrointestinal x-ray, endoscopy, and, in selected cases, a sur gical second look). Methods. Fifty-nine patients with a rise in carcin oembryonic antigen serum levels or a clinical suspicion of recurrences entered the study. Scintigraphy was performed at multiple interval ti mes (4-100 hours) after an intravenous injection of radiolabelled FO23 C5 F(ab')(2) fragments. Results. The cumulative results showed the hig h sensitivity (89%), specificity (78%), and accuracy (86%) of radioimm unodetection. Of the radiologic methods, only magnetic resonance imagi ng had the same accuracy (86%), with lower specificity (64%) and highe r sensitivity (93%). Computed tomographic scan and ultrasonography dis played the poorest accuracy (68% and 47%, respectively). Conclusions. Radioimmunodetection is an important imaging technique that can be use d in clinical practice for the follow-up of the patient with colorecta l carcinoma.