Role of In-111 labeled CYT-103 immunoscintigraphy in the evaluation of patients with recurrent colorectal carcinoma

An immunoconjugate of the whole antibody, B72.3, has been approved by the FDA. It is labeled with indium-111, which allows imaging studies intended for the diagnosis and staging of colorectal and recurrent ovarian carcinoma. The new diagnostic imaging agent (CYT-103), Oncoscint CR/OV, has found particular use in evaluating patients with recurrent carcinoma. The three major indications for the study are: 1) occult disease-unexplained rise in serum tumor markers (e.g. CEA), with negative work-up including CT; 2) known local recurrence (e.g. liver or rectal area)-surgery is planned, but there is a need to rule out other areas of involvement; 3) clarify equivocal CT or MRI finding-to distinguish whether an abnormality is due to recurrent tumor or scar tissue, fibrosis, or unopacified bowel loop. Oncoscint has proven to be more sensitive than CT in the detection of disease in the pelvis and extrahepatic abdomen. CT remains the modality of choice for the detection of liver metastases. The combined sensitivity of the two modalities is 88% on a per-patient basis.