Doctors are seeking ways to improve the accuracy of positron-emitting tomography (PET) scanning for assessing the extent of disease in patients with colon cancer. One possible way to accomplish this goal is by attaching a radioactive substance that can be detected by PET scanning to an antibody that targets colon cancer cells. In this study, investigators are determining the usefulness of a monoclonal antibody called huA33 for diagnosis and for detecting the presence of a protein called the A33 antigen. HuA33, an antibody made in a laboratory, appears to attach itself to colon cancer cells, and may trigger the immune system to kill these cells. Radioactive iodine 124 (124I) labeled to A33 can be detected by PET scanning.
The aims of this study are to see: (1) if huA33 attached to 124I can be safely given to patients with colorectal cancer, (2) if the radioactivity binds only to cancer cells, and not normal cells, and (3) if the measurement of radioactivity made with the PET scanner is the same as the radioactivity detected when the tumor is surgically removed from the body and counted using a gamma counter. Researchers will determine how well huA33 targets colon cancer cells. Ultimately, if huA33 tagged with 124I is safe for patients and targets only cancer cells, this approach may lead to a more accurate way to determine the spread of colon cancer.