CEA Biomarker

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What is CEA? How is CEA a biomarker?

CEA stands for carcinoembryonic antigen. CEA is made by cells in the gastrointestinal tract and released into the blood. Generally, CEA is exclusively produced during embryonic development and healthy adults have relatively low levels of CEA. However, CRC cells can also produce CEA, making it a biomarker for CRC.   

Your CEA level is considered a prognostic and predictive biomarker. All CRC patients should receive testing for CEA levels. 

What does my CEA level mean?

It is important to note that a high CEA level does not immediately indicate colorectal cancer and a low CEA level does not immediately rule out colorectal cancer.  

High CEA levels can also be found in some benign (non-cancerous) digestive system diseases, cigarette smokers, or other types of cancer. CEA levels are not always increased in colorectal cancer. More than 10% of colorectal cancer patients will have a normal CEA level.  

CEA levels are reported as a number, most often as the amount of CEA found in a specific amount of blood. Generally, normal CEA levels are between 0 and 2.9 ng/mL (nanograms per milliliter). However, this range may vary depending on laboratory/clinician or other individual circumstances.  

CEA levels above the normal range will either be considered low or high.  

  • Low CEA levels may indicate a small tumor or that the tumor is not producing CEA. Low CEA levels alone are not enough to diagnose. A low CEA level may prompt your doctor to order additional tests, such as imaging by MRI. 
  • High CEA levels could indicate a large tumor or metastatic disease. CEA levels tend to increase with cancer stage. High CEA levels alone are not enough to diagnose, stage, or determine metastasis. High levels of CEA are associated with a poorer prognosis. 

How does a CEA test work? How often should I get my CEA level checked?

CEA levels are most commonly checked using a traditional blood test. A small blood sample will be sent to the laboratory to be analyzed for CEA levels.  

Checking your CEA levels may be recommended by your medical care team throughout your care. Common times your healthcare provider may recommend checking your CEA levels are: 

  • Immediately after diagnosis (sometimes referred to as baseline testing) – getting your CEA levels checked at time of diagnosis can provide a baseline level to help guide your treatment.  
  • Before / after surgery – getting your CEA levels checked before and after surgery can help determine whether the surgery was successful.  
  • During treatment – getting your CEA levels checked during treatment can help determine how well the treatment is working. 
  • After completion of treatment – getting your CEA levels checked after you complete treatment can help determine if your cancer has returned, or recurred.  

During active treatment, CEA levels are often checked every one to three months.  

During remission, you may need regular checks for your CEA levels. The frequency of testing is most often decided by your medical care team. Often times, the follow up for checking CEA levels is as follows:

  • every 3 – 6 months for the first 2 years
  • every 6 months during the following year
  • every year afterwards for the following two years, for a total of 5 years

My CEA level is going up: What does that mean?

Increasing levels of CEA during treatment may be a sign of cancer progression (either tumor growth or metastasis). It is important to note that CEA levels may increase at the beginning of treatment (often during the first four to six weeks) and then decrease. This phenomenon is often called a “CEA flare.”  

Increasing CEA levels after completion of treatment may be a sign of cancer recurrence. If you experience an increase in CEA levels after treatment completion, your medical care team will do more testing to confirm or rule out recurrence. 

My CEA level went down: What can that mean?

Decreasing CEA levels is often a sign that your current treatment is working. CEA levels will usually decrease following a successful surgery. 

Is CEA used exclusively for colorectal cancer patients, or is it used in other cancers?

CEA testing is not exclusive to colorectal cancer patients. Medical care providers may use CEA in patients with other cancers, including bladder, breast, lung, ovarian, and thyroid cancers as examples. 

Medical Review

Al B. Benson III, MD

Lurie Cancer Center – Northwestern

Last Reviewed: October 11, 2023
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