From the Guidelines
Normal levels of carcinoembryonic antigen (CEA) are typically less than 5 mg/mL, as elevated levels (≥ 5 mg/mL) may correlate with poorer prognosis in patients with colorectal carcinoma. The provided evidence from the 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer 1 does not explicitly state the normal level of CEA, but it does mention that elevated preoperative CEA (≥ 5 mg/mL) may correlate with poorer prognosis. However, based on general medical knowledge and the context of CEA as a tumor marker, it is known that normal levels of CEA in healthy adults are typically less than 2.5 ng/mL for non-smokers and less than 5.0 ng/mL for smokers. CEA is a protein found in the tissues of a developing baby, and levels normally become very low or undetectable in adults. Certain conditions can cause elevated CEA levels, including colorectal cancer, pancreatic cancer, lung cancer, breast cancer, and some non-cancerous conditions like inflammatory bowel disease, pancreatitis, liver disease, and smoking. CEA is primarily used as a tumor marker to monitor treatment response and detect recurrence in patients with certain cancers, particularly colorectal cancer, as stated in the guideline recommendations 1. It's essential to note that CEA is not recommended as a screening test for cancer in the general population because it lacks sensitivity and specificity for early cancer detection, as mentioned in the guideline recommendations for CEA as a marker for colorectal cancer 1. Interpretation of CEA levels should always be done in the context of a patient's complete clinical picture and other diagnostic tests. Key points to consider when interpreting CEA levels include:
- Elevated CEA levels (≥ 5 mg/mL) may correlate with poorer prognosis in patients with colorectal carcinoma
- CEA is not recommended as a screening test for cancer in the general population
- CEA is primarily used as a tumor marker to monitor treatment response and detect recurrence in patients with certain cancers
- Interpretation of CEA levels should always be done in the context of a patient's complete clinical picture and other diagnostic tests.
From the Research
Normal Levels of Carcinoembryonic Antigen (CEA)
- The normal level of CEA is generally considered to be less than 2.5 ng/mL for non-smokers and less than 5.0 ng/mL for smokers 2.
- A study published in JAMA in 1981 found that normal CEA levels (less than 2.5 ng/mL) occurred in 55% of patients with limited disease compared to 12% of patients with extensive disease 3.
- Another study published in 1997 found that the postoperative levels of CEA were evaluated to ascertain their potency in predicting the recurrence of colorectal cancer after curative surgery, and the patients with postoperative CEA levels less than 5 ng/mL had better disease-free survival rates 4.
- A study published in 2015 found that elevated CEA levels (>5 ng/mL) were a significant negative predictor of downstaging after chemoradiotherapy and also had a negative impact on recurrence-free survival in rectal cancer 5.
- The normal levels of CEA can vary depending on the assay used, with one study finding that the normal levels were 2.3 microgram/1 and 3.3 microgram/1 using two different assays 6.