Comparison of radioimmunodetection with other imaging methods in evaluating local relapses of colorectal carcinoma.

BACKGROUND

The prognosis for colorectal cancer patients is related closely to the extent of tumor at the time of diagnosis, and early detection of metastatic or recurrent disease is an important prerequisite for successful treatment. Radioimmunodetection is a relatively new technique to image colorectal cancer using radiolabelled monoclonal antibodies (MoAb). The goal of this study was to evaluate the clinical use of radioimmunodetection with the anti-carcinoembryonic antigen MoAb FO23C5, radiolabelled with 131I, in patients submitted to surgery for colorectal cancer and with suspected local recurrences. The results of radioimmunodetection were compared with those of computed tomography, ultrasonography, magnetic resonance imaging, and other diagnostic techniques (gastrointestinal x-ray, endoscopy, and, in selected cases, a surgical second look).

METHODS

Fifty-nine patients with a rise in carcinoembryonic antigen serum levels or a clinical suspicion of recurrences entered the study. Scintigraphy was performed at multiple interval times (4-100 hours) after an intravenous injection of radiolabelled FO23C5 F(ab')2 fragments.

RESULTS

The cumulative results showed the high sensitivity (89%), specificity (78%), and accuracy (86%) of radioimmunodetection. Of the radiologic methods, only magnetic resonance imaging had the same accuracy (86%), with lower specificity (64%) and higher sensitivity (93%). Computed tomographic scan and ultrasonography displayed the poorest accuracy (68% and 47%, respectively).

CONCLUSIONS

Radioimmunodetection is an important imaging technique that can be used in clinical practice for the follow-up of the patient with colorectal carcinoma.