Pitfalls in antibody imaging in colorectal cancer

Monoclonal antibodies against tumor-associated antigens can be conjugated to radionuclides and used to localize tumors in vivo. This technique may be useful in identifying recurrent disease that cannot be demonstrated using conventional studies such as computerized tomography. The literature suggests that the use of antibody fragments and SPECT imaging will increase the diagnostic yield. The choice of radionuclide may vary depending on the region of interest. Factors that influence the success of imaging include the experience of individuals interpreting the scan and the level of tissue antigen expression. Antibodies of murine origin may produce a human antimouse antibody response after imaging, causing allergic responses, interference with subsequent imaging or results of standard in vitro laboratory tests. Finally, false-positive images occur in more than 10% of patients. Current studies in patients with colorectal cancer should focus on determining if changes in management resulting from antibody imaging have a positive effect on either patient survival or quality of life.