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Overview

Colorectal cancer is one of the most common gastrointestinal malignancies, ranking among the leading causes of cancer incidence and mortality worldwide, including in Vietnam. Early detection and post-treatment surveillance are vital for improving patient prognosis.

One of the most frequently used blood tests for monitoring patients is CEA (Carcinoembryonic Antigen). This glycoprotein is normally produced during fetal development; however, in healthy adults, its levels are typically very low. Elevated CEA levels can indicate the presence of certain cancers, particularly colorectal cancer.

What is CEA?

• Carcinoembryonic Antigen (CEA): An oncofetal antigen secreted by mucosal cells during fetal life.

• In healthy adults, CEA is either undetectable or present at very low concentrations in the bloodstream.

• When cancer cells develop abnormally, especially in the colon or rectum CEA levels may rise, serving as a clinical tumor marker.

Normal Reference Ranges

• Non-smokers: < 3 ng/mL.

• Smokers: < 5 ng/mL.

If levels exceed these thresholds, clinicians must investigate various causes, as elevation is not exclusive to cancer.

Causes of Elevated CEA

1. Malignancies

• Colorectal cancer (the most common association).

• Other cancers: Lung, pancreatic, gastric, breast, and liver cancer.

2. Benign Conditions

• Chronic inflammatory bowel disease (Crohn’s disease, ulcerative colitis).

• Hepatitis, cirrhosis, or pancreatitis.

• Chronic lung disease.

• Long-term tobacco use.

👉 Note: Because CEA is not specific to colorectal cancer, it must be interpreted alongside colonoscopy, biopsy, and other diagnostic imaging.

Clinical Significance in Colorectal Cancer

1. Screening

• CEA is not recommended for screening the general population due to its limited sensitivity and specificity.

• Colonoscopy remains the gold standard for screening.

2. Diagnosis

• CEA alone cannot confirm a diagnosis of colorectal cancer.

• However, high levels (> 10 ng/mL) in patients with suspicious findings on an endoscopy or imaging can strongly suggest malignancy.

3. Prognosis

• Pre-operative CEA levels are often correlated with the disease stage.

• Higher levels typically indicate a greater risk of recurrence or metastasis.

• For instance, levels > 20 ng/mL often suggest advanced or spread disease.

4. Post-treatment Monitoring

This is the most critical role of CEA.

• After a tumor is surgically removed, CEA levels usually return to normal within 4–6 weeks.

• A subsequent rise in levels may be the first sign of recurrence or metastasis.

• Recommendation: Post-operative patients should have CEA levels measured every 3–6 months for the first 5 years.

Limitations of the CEA Test

• Low Sensitivity: CEA levels remain normal in some cancer patients (affecting 40–80% of cases).

• Low Specificity: Elevated levels can occur in many benign conditions or other types of cancer.

• No Substitute for Biopsy: It cannot replace colonoscopy and biopsy for definitive diagnosis.

When should you get a CEA test?

• Patients already diagnosed with colorectal cancer: To monitor treatment efficacy and detect recurrence.

• Pre-surgery or pre-treatment: To assess disease severity and prognosis.

• Post-treatment: Periodic testing for long-term disease control.

Note: A CEA test should never be used as the sole basis for diagnosing cancer, especially in healthy individuals.

Procedure of a CEA test

1. A standard venous blood draw is used.

2. Fasting is not required.

3. Results are typically available within 1–2 days.

Conclusion

CEA is a valuable biomarker for prognostic assessment and the long-term monitoring of colorectal cancer. It is most effective when used as part of a comprehensive diagnostic plan including endoscopy, imaging, and pathology.

👉 For patients who have undergone treatment, regular CEA monitoring is essential for early detection of recurrence, significantly improving the chances of successful intervention.

FAQ

1. Can CEA be used to screen for colorectal cancer?

No. Colonoscopy is the standard and most effective method for screening.

2. What CEA level indicates a suspicion of cancer?

Levels above 10 ng/mL, and especially above 20 ng/mL, indicate a high risk. However, a diagnosis still requires confirmation via colonoscopy and biopsy.

3. How soon after surgery should CEA be measured?

Initially at 4–6 weeks post-op to establish a baseline, then every 3–6 months for at least the first 5 years.

4. What does it mean if CEA rises after surgery?

It may signal that the cancer has returned or spread. Your doctor will likely order a CT or PET-CT scan for further investigation.

5. Do smokers have higher CEA levels?

Yes. Smokers can have a "normal" baseline of up to 5 ng/mL. Doctors must account for smoking habits when interpreting results.

To schedule an appointment for CEA tumor marker testing and consultation at DYM Medical Center Vietnam, please contact us via:

• DYM Medical Center Saigon: Room B101-B103, Basement 1, mPlaza Saigon Building, No. 39 Le Duan, Sai Gon Ward, Ho Chi Minh City

• DYM Medical Center Phu My Hung: Room 3A01, 3A Floor, The Grace Building, 71 Hoang Van Thai Street, Tan My Ward, Ho Chi Minh City

• DYM Medical Center Hanoi: B1 Basement, Epic Tower, Alley 19 Duy Tan, Cau Giay Ward, Ha Noi

• Hotline: 1900 29 29 37