Radioimmunodetection of occult carcinoembryonic antigen-producing cancer.

This study evaluates the ability of 111In-labeled anti-carcinoembryonic antigen (CEA) monoclonal antibody (Mab) ZCE-025 to detect sites of occult cancer in patients with elevated serum CEA who have negative or equivocal CT scans. One hundred forty patients suspected of having occult cancer were evaluated. Except for elevated CEA levels, all had negative work-ups, including negative or inconclusive CT scans. Eighty-two patients (59%) had positive scans and 58 (41%) had negative scans. Seventy-five of the 82 patients with positive scans had confirmation of at least one Mab-positive lesion (91% positive predictive value). Thirty-eight of the 58 patients with negative scans had negative follow-up (66% negative predictive value). The Mab scan correctly identified at least one site of tumor in 75 of the 95 patients with recurrent or metastatic disease (79% sensitivity) and correctly predicted the absence of disease in 38 of 45 patients (84% specificity).