Circulating immune complexes (CIC), carcinoembryonic antigen (CEA) and CIC containing CEA as markers for colorectal cancer.

It has been suggested that circulating immune complexes (CIC) would provide a useful tumour marker system and that carcinoembryonic antigen (CEA) may form an antigen component of CIC found in patients with colorectal cancer. In this study the clinical usefulness of CIC and CIC containing CEA (CEA-IC) was investigated. Concentrations of CIC were measured in 30 patients with colorectal cancer. Fourteen patients were studied sequentially at approximately 1 month intervals after apparent curative resection of the primary tumour. Results were correlated with those obtained from serum CEA and compared to clinical status. CEA-IC were measured using a novel assay and compared with CIC and CEA values in 29 patients. CIC concentrations were elevated in patients with known disease and predicted clinical relapse in four of 14 patients. In two patients CIC remained elevated despite sustained remission. CEA-IC were not detectable in any of the patients studied. CIC estimations may augment CEA measurements as indicators of disease recurrence but lack of specificity makes them of little practical value as tumour markers in colorectal cancer. No evidence was found to support previous reports that CEA was an antigen component of CIC in this disease.