Artifactual CEA elevation due to human anti-mouse antibodies
B. A. Morton, M. O'Connor-Tressel, B. G. Beatty, J. E. Shively and J. D. Beatty
Department of General Oncologic Surgery, City of Hope National Medical Center, Duarte, CA 91010.
Retrospective analysis of 108 patients who received indium 111-labeled
murine monoclonal antibodies for imaging of cancer was performed. Most
patients had operative procedures for colorectal carcinoma following
completion of scintiscanning. Eleven patients had markedly elevated
carcinoembryonic antigen (CEA) levels postoperatively without evidence of
residual or recurrent disease. The laboratory method of measuring CEA
levels was a commercially available double mouse monoclonal antibody enzyme
immunoassay. It was postulated that the unexplained elevation of CEA was a
reflection of the presence of human anti-mouse antibody (HAMA) induced by
the administration of radiolabeled mouse antibody. A competitive assay for
HAMA was undertaken by incubation of these patients' sera with a high dose
of nonspecific mouse immunoglobulin prior to CEA determinations, and
subsequent CEA levels were normal. The presence of HAMA was confirmed by a
noncompetitive solid-phase enzyme immunoassay in 73% of tested patients who
received murine monoclonal antibodies for imaging. Identification of
artifactual CEA elevations is important in the treatment of cancer
patients.
