Immunoscintigraphy performed with In-111-labeled CYT-103 in the management of colorectal cancer: comparison with CT

Immunoscintigraphy performed after intravenous administration of indium-111-labeled CYT-103, an immunoconjugate of monoclonal antibody B72.3, was evaluated in patients with suspected primary or recurrent colorectal cancer at 25 centers in the United States. Gamma camera imaging, computed tomography (CT), and confirmatory surgical exploration were completed in 169 of 227 patients who received single infusions of In-111 CYT-103. Eight patients (3.5%) had reversible, nonserious adverse reactions, and 39% developed antimurine antibodies. Surgery revealed that 155 of 169 patients had colorectal carcinoma. In these 155 patients, immunoscintigraphy and CT demonstrated similar sensitivity (69% and 68%, respectively) and specificity (77%). However, immunoscintigraphy had greater sensitivity in detection of pelvic tumors (74% vs 57%, P = .035) and extrahepatic abdominal tumors (66% vs 34%, P less than .001); CT enabled detection of a greater proportion of liver metastases (84% vs 41%, P less than .001). These results indicate that In-111 CYT-103 can be administered safely and that immunoscintigraphy performed with this agent frequently enables identification of extrahepatic abdominal sites of disease not visualized with CT.