Carcinoembryonic Antigen Test
Carcinoembryonic antigen (CEA) is a tumor-associated antigen characterized as an oncofetal glycoprotein of approximately 200,000 molecular weight with Beta electrophoretic mobility, a single protein chain of about 800 amino acids, and 50-80% carbohydrate composition. CEA was first present as a specific antigen for adenocarcinoma of the colon. More recent studies have demonstrated CEA presence in a variety of malignancies, particularly those involving ectodermal tissues of gastrointestinal or pulmonary origin. Small amounts have also been demonstrated in secretions from the colonic mucosa. Additionally, CEA-like substances have been reported in normal bile from non-icteric patients. CEA testing can have significant value in the monitoring of patients. Persistent elevation in circulating CEA following treatment is strongly indicative of occult metastic and/or residual disease. A persistent rising CEA value may be associated with progressive malignant disease and poor therapeutic response. A declining CEA value is generally indicative of a favorable prognosis and good response to treatment. Measurement of CEA has been shown to be clinically relevant in the follow-up management of patients with colorectal, breast, lung, prostatic, pancreatic, ovarian, and other carcinomas. Follow-up studies of patients with colorectal, breast and lung carcinomas suggest that the preoperative CEA level has prognostic significance.