Multicenter clinical trials of monoclonal antibody B72.3-GYK-DTPA 111In (111In-CYT-103; OncoScint CR103) in patients with colorectal carcinoma.

The results of this clinical trial involving 23 sites indicated that 111In-CYT-103 immunoscintigraphy identified 70% of all patients with surgically confirmed disease when interpreted by the on-site physician. The sensitivity of 111In-CYT-103 imaging was slightly lower when interpreted retrospectively by the blinded readers in the absence of any patient-specific information. 111In-CYT-103 imaging sensitivity was similar in patients with primary and recurrent disease, but lower for liver metastases than for extrahepatic disease. Thirty-three previously unknown lesions were visualized by immunoscintigraphy; tissue confirmation was available for only five lesions, and all were found to be free of tumor. Only one of the lesions evaluated was TAG-72 positive. Twenty-eight lesions were outside the surgical field or not biopsied. Although no tissue confirmation was available, seven (25%) of these lesions were identified as consistent with metastatic disease by other conventional modalities. Importantly, antibody scans detected occult tumor lesions in 11 of the 92 patients with surgically confirmed adenocarcinoma, and accurately diagnosed 7 of 10 patients with elevated serum CEA levels and negative conventional workup. Surgery confirmed the presence of tumor identified only by 111In-CYT-103 in three patients, while four patients with negative scans had no evidence of recurrent disease at surgery. Antibody scans confirmed the absence of additional disease in 18 of 22 patients with isolated hepatic or pelvic recurrences in whom curative surgery was contemplated. The results of this multicenter trial suggest that CYT-103 immunoscintigraphy can provide information that is complementary to that derived from standard diagnostic techniques. During the workup of patients with primary colorectal carcinoma, this modality assesses the entire body and allows for the identification of multiple lesions at various locations simultaneously. It can then redirect attention and further workup to those areas not originally surveyed. Of special interest in this regard is the identification of occult lesions in five patients with primary colorectal cancer. 111In-CYT-103 imaging was found superior to CT in the localization of primary colorectal cancer, but neither modality could adequately assess the extent of tumor penetration through the bowel wall (the T stage in the TNM system) or the N status. The limitations of CT in evaluating T and N are well documented, and the limitations of 111In-based immunoscintigraphy for these same lesions have recently been described. Another limitation of 111In-CYT-103 immunoscintigraphy is in the identification of liver metastases.(ABSTRACT TRUNCATED AT 400 WORDS)