Serum CEA in the management of recurrent colorectal cancer.

While cell surface antigens restricted to cancer cells have not yet been identified, a number of antigens have been described which are present in greater amounts in association with cancer cells. CEA is present on the cell surface of the majority of colorectal cancers and is released into the serum where it can be used to monitor for disease recurrence. The presence of CEA on the cell surface can be used to localise the site of tumour recurrence by antibody/isotope conjugate scanning. A fall in serum CEA after treatment with cytotoxic chemotherapy can be used to predict patients whose survival will be prolonged by the chemotherapy. As more effective treatments of disseminated colorectal carcinoma are developed, serum CEA may play an increasing role in monitoring response to treatment.