Serum CEA (Carcinoembryonic Antigen)

Function

Carcinoembryonic Antigen (CEA) is a glycoprotein involved in cell adhesion. It is normally produced during fetal development, but production stops or decreases significantly after birth. In adults, elevated levels of CEA are often associated with certain types of cancer, particularly those originating in the gastrointestinal tract. While not used for general cancer screening due to its lack of specificity, it serves as a powerful biomarker for disease management.

Why it is Ordered

CEA is primarily used as a longitudinal tool rather than a diagnostic one:

• Monitoring Treatment: To assess how well a patient is responding to cancer therapy (surgery, chemotherapy, or radiation).
• Recurrence Surveillance: Following successful treatment, rising CEA levels are often the first sign that a cancer has returned, sometimes months before imaging can detect a tumor.
• Prognosis: High baseline CEA levels at the time of diagnosis may correlate with a more advanced stage of cancer and a poorer clinical outlook.
• Staging: Assisting in determining the extent of cancer spread, especially in colorectal malignancies.

Associated Conditions

Elevated CEA levels are most significantly associated with:

• Colorectal Cancer: The primary use case for this marker.
• Other Malignancies: Including pancreatic, lung, breast, and thyroid cancers.
• Non-Malignant Conditions: CEA can also rise in benign conditions such as heavy smoking, inflammatory bowel disease (IBD), cirrhosis of the liver, and chronic obstructive pulmonary disease (COPD).