Carcinoembryonic antigen, known as CEA, is a protein found in the human body. While present during fetal development, its levels typically become very low or undetectable in healthy adults. However, in certain conditions, particularly various cancers, CEA levels can become noticeably elevated.
What is Carcinoembryonic Antigen?
Carcinoembryonic antigen is a glycoprotein found on the surface of cells. During fetal development, CEA plays a role in cell adhesion, helping cells stick together. After birth, the genes responsible for producing CEA are typically turned off, leading to its minimal presence in healthy adult tissues and blood.
When certain cancer cells begin to grow and divide uncontrollably, they can reactivate the production of CEA. This reactivation makes CEA a useful tumor marker, often associated with cancers of the gastrointestinal tract, lungs, and breasts. Elevated CEA in adults can therefore indicate specific cancerous processes, providing a measurable indicator for clinical assessment.
CEA and Brain-Related Conditions
CEA levels can be elevated in the presence of brain tumors, especially metastatic ones. Cancers originating in the colon, lung, or breast are among the most common types that can metastasize to the brain, and these cancers often produce CEA. When these metastatic cells reach the brain, they can continue to release CEA.
Monitoring CEA levels is particularly useful for individuals with a known history of these primary cancers to assess if the disease has spread to the brain or if existing brain metastases are progressing. For instance, a rise in CEA levels in a patient previously treated for colorectal cancer might prompt imaging studies of the brain to check for new or growing lesions. While CEA is a useful indicator for metastatic brain disease, primary brain tumors rarely produce CEA themselves.
Measuring CEA Levels
Measuring CEA levels primarily involves a simple blood test, where a sample of blood is drawn from a vein. The CEA protein circulates in the bloodstream, and its concentration can be quantified in the serum component of the blood. This serum CEA test is a common method for initial assessment and ongoing monitoring.
When there is a suspicion of direct involvement of the brain or spinal cord, a cerebrospinal fluid (CSF) CEA test may be performed. CSF is the fluid that surrounds the brain and spinal cord, and a sample is obtained through a lumbar puncture, often called a spinal tap. Measuring CEA directly in the CSF can provide more localized information about the presence of cancer cells within the central nervous system.
Understanding CEA Test Results
Interpreting CEA test results involves considering them within the broader clinical context. Elevated CEA levels may suggest the presence of cancer, its recurrence, or progression, particularly in the context of brain metastases. For example, a significant increase in CEA levels in a patient with a history of lung cancer could indicate new or growing tumors in the brain.
CEA is not a standalone diagnostic tool for cancer or brain conditions. A high CEA level does not definitively diagnose cancer; instead, it serves as a marker that prompts further investigation. Doctors always interpret CEA results in conjunction with other clinical findings, such as patient symptoms, imaging scans, and tissue biopsies, to reach an accurate diagnosis. Certain non-cancerous conditions, including inflammation, liver disease, or even heavy smoking, can cause mild elevations in CEA levels, a factor considered during interpretation.