Carcinoembryonic Antigen (CEA) is a protein that serves as a tumor marker, meaning its levels can be elevated in the presence of certain cancers. While it is naturally present in fetal tissue, its levels typically become very low or undetectable in healthy adults. An increase in CEA levels in adults can indicate various conditions, both cancerous and non-cancerous.
Understanding CEA Levels
CEA levels are measured in nanograms per milliliter (ng/mL) of blood. For healthy non-smokers, a normal CEA level is between 0 and 2.5 ng/mL. Individuals who smoke often have naturally higher baseline levels, with a normal range extending up to 5 ng/mL. These ranges can vary slightly between different laboratories.
Elevated CEA levels warrant further medical investigation, but they do not definitively diagnose cancer. Levels between 3 ng/mL and 10 ng/mL in non-smokers (or 5-10 ng/mL in smokers) might suggest a small, localized tumor or could be due to non-cancerous health conditions. Levels exceeding 10 ng/mL often indicate advanced or spreading cancer, particularly colorectal cancer, but this still requires comprehensive clinical evaluation.
Common Causes of Elevated CEA
Elevated CEA levels can stem from a variety of causes, encompassing both cancerous and non-cancerous conditions. Non-cancerous causes include inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis. Pancreatitis, liver diseases like cirrhosis or hepatitis, and chronic obstructive pulmonary disease (COPD) can also result in elevated CEA. Smoking is a common non-cancerous cause. These non-cancerous elevations are mild to moderate, often remaining below 10 ng/mL.
Cancerous causes include colorectal cancer, where CEA levels are most commonly associated. Elevated CEA can also be seen in other cancers, including those of the lung, breast, ovary, pancreas, stomach, and thyroid. Higher CEA levels are often linked to more advanced cancer stages or spread.
CEA’s Application in Cancer Management
CEA testing is not used for general cancer screening or initial diagnosis. This is because many non-cancerous conditions can elevate CEA, making it an unreliable stand-alone diagnostic tool.
Its primary clinical utility lies in monitoring cancer patients who have already received a diagnosis. Healthcare providers use CEA levels to track the effectiveness of cancer treatments like chemotherapy, immunotherapy, or radiation therapy. A decrease in CEA levels during treatment suggests the therapy is working, while persistently high or rising levels may indicate the cancer is not responding or is progressing. CEA testing is also valuable for detecting cancer recurrence after treatment, with rising levels signaling the return of the disease. For certain cancers, particularly colorectal cancer, CEA levels can also provide information about prognosis.
Interpreting CEA Test Results
Interpreting CEA test results requires a comprehensive approach by a healthcare professional. A single CEA value should not be viewed in isolation; it must be considered alongside other diagnostic tests, such as imaging studies and biopsies, as well as the patient’s medical history and physical examination findings. This integrated approach helps establish a complete clinical picture.
CEA levels can vary among individuals and even within the same person due to factors like age and other medical conditions. Observing the trend of CEA levels over time, rather than focusing on a single measurement, provides more meaningful information. A consistent rise or fall in CEA levels is more indicative of changes in a patient’s condition than an isolated result. CEA is not a perfect marker; not all cancers lead to elevated CEA, and an elevated level does not always signify cancer.