MoAb May Improve Detection of Colon And Rectal Cancer

BOSTON--A radiolabeled monoclonal antibody (MoAb) currently underinvestigation may improve detection of recurrent colorectal cancer,said Dr. Frederick Moffat, associate professor of surgery, Universityof Miami Medical School.

Results of a multicenter study, reported by Dr. Moffat at the48th Annual Cancer Symposium of the Society of Surgical Oncology(SSO), suggest that use of the radiolabeled antibody may complementCT scans in the detection of early recurrence of disease. A clinicalbenefit of the MoAb was found in 42% of 210 patients studied.

The diagnostic agent, called CEA-Scan (formerly known as ImmuRAID-CEA),is produced by Immunomedics, Inc., Morris Plains, NJ, and is currentlyunder review for marketing approval in the United States and Europe.

Use of CEA-Scan in addition to CT studies may help doctors determinewhether the patient is a good candidate for surgery, and may alsodirect the surgeon to metastases missed with CT scan alone (seefigure), Dr. Moffat said. He believes that "CT scanis overrated for the detection of recurrent colorectal cancer,"and that antibody-aided visualization will improve the detectionof recurrent and metastatic disease.

CEA-Scan is a technetium-99m labeled antibody fragment that recognizescarcinoembryonic antigen (CEA), a tumor marker for colorectalcancer and some breast and lung cancers. Because CEA-Scan is anantibody fragment, it avoids many of the problems that plagueother antibody-assisted imaging techniques, such as toxicity andthe production of human antimouse antibodies (HAMA), he said.Also, serum CEA levels do not adversely affect imaging efficacy.

Since CEA-Scan is labeled with technetium-99, it is relativelyinexpensive and easy to use, he said. The radiolabel can be injectedinto the antibody vial just prior to administration, and the wholeprocedure can be done on an outpatient basis.

Immunomedics, Inc. is currently evaluating the use of CEA-Scanfor breast and lung cancers. In addition, the company has justreceived an NCI grant to determine the clinical efficacy of ahumanized lymphoma-targeting antibody for therapy, according toexecutive vice president Amy Factor.