Immunology and immunotherapy of colorectal cancer

Adenocarcinoma of the human colon produce carcinoembryonic antigen (CEA), one of a family of glycoprotein molecules that may be produced by various human cancers and, occasionally, by other abnormal tissues. The physicochemical nature and tissue distribution of CEA have been well established and a variety of radioimmunoassays have been developed for the detection of this material in the circulation of patients with CEA-producing tumours. Although the assay should not be used as a screening test for cancer of the bowel, it may serve as a helpful adjunct in the diagnosis of digestive system tumours in conjunction with other routine investigations. More important is the utilization of the radioimmunoassay for CEA under the following circumstances: 1. Preoperatively as an indicator of tumour dissemination based upon the quantitative concentrations of CEA in the circulation. 2. As an indicator of potentially curative resection manifested by a decrease in circulating concentrations of CEA to below detectable limits. 3. As an early warning of recurrent tumour growth, by detecting the reappearance of CEA in the circulation of a patient rendered CEA-negative after tumour resection, 3 months to 2 years or more before any other presently available technology can detect clinical evidence of recurrence. This last observation is now under investigation for its potential value as an indicator for second-look surgery in patients who have undergone potentially curative surgery for colorectal cancers.