Faecal carcinoembryonic antigen in colorectal cancer patients.

Carcinoembryonic antigen (CEA) has been measured in the faeces of large bowel cancer patients and control subjects to determine whether this measurement might be a useful aid in the diagnosis of large bowel cancer. The mean faecal CEA in 24 cancer patients fell significantly from 10.43 +/- 2.39 micrograms/g pre-operatively to 3.61 +/- 0.72 micrograms/g postoperatively (p less than 0.05). Pre-operative values were not related to either tumour stage or serum CEA. In 20 patients with no known colorectal disease the mean faecal CEA was 5.43 +/- 1.95 micrograms/g which was significantly lower than the mean pre-operative value in the cancer patients (p less than 0.05). In 14 patients with a variety of benign colonic diseases the mean faecal CEA was 7.12 +/- 1.39 micrograms/g which was not significantly different from the mean pre-operative value in the cancer patients. Considerable overlap of values was observed between individual cancer and control patients making the test, as presently carried out, non-discriminatory. If the potential for making the test more cancer specific can be realised, however, faecal CEA determination may permit discrimination between cancer and non-cancer patients at a relatively early stage of disease.