BOSTON--A radiolabeled monoclonal antibody (MoAb) currently under
investigation may improve detection of recurrent colorectal cancer,
said Dr. Frederick Moffat, associate professor of surgery, University
of Miami Medical School.
Results of a multicenter study, reported by Dr. Moffat at the
48th Annual Cancer Symposium of the Society of Surgical Oncology
(SSO), suggest that use of the radiolabeled antibody may complement
CT scans in the detection of early recurrence of disease. A clinical
benefit 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 currently
under review for marketing approval in the United States and Europe.
Use of CEA-Scan in addition to CT studies may help doctors determine
whether the patient is a good candidate for surgery, and may also
direct the surgeon to metastases missed with CT scan alone (see
figure), Dr. Moffat said. He believes that "CT scan
is overrated for the detection of recurrent colorectal cancer,"
and that antibody-aided visualization will improve the detection
of recurrent and metastatic disease.
CEA-Scan is a technetium-99m labeled antibody fragment that recognizes
carcinoembryonic antigen (CEA), a tumor marker for colorectal
cancer and some breast and lung cancers. Because CEA-Scan is an
antibody fragment, it avoids many of the problems that plague
other antibody-assisted imaging techniques, such as toxicity and
the 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 relatively
inexpensive and easy to use, he said. The radiolabel can be injected
into the antibody vial just prior to administration, and the whole
procedure can be done on an outpatient basis.
Immunomedics, Inc. is currently evaluating the use of CEA-Scan
for breast and lung cancers. In addition, the company has just
received an NCI grant to determine the clinical efficacy of a
humanized lymphoma-targeting antibody for therapy, according to
executive vice president Amy Factor.