- CEA or Carcinoembryonic antigen is a protein found in embryonic or fetal tissue.
- Serum levels disappear almost wholly after birth, but small amounts may be present in the colon.
- In adults it may be raised in malignancies associated with the protein, especially mucinous cancers associated with the GI tract or ovary.
ROLE IN SCREENING FOR COLORECTAL CANCER
- CEA/Carcinoembryonic antigen is not a screening tool to diagnose colorectal or any other cancer.
- Best screening tool for colorectal cancer/CRC is colonoscopy.
- Fecal occult blood testing & per rectal examination are also used as screening tools.
- CEA is usually measured AFTER a diagnosis of CRC is made.
Malignancies causing an elevated CEA
- Gastrointestinal tract
- Malignant pseudomyxoma peritonei
Benign conditions causing an elevated CEA
- Peptic ulcer
- Cigarette smoking
- Mucinous cystadenoma of the ovary or appendix
- Liver cirrhosis
- Inflammatory bowel disease
- Pulmonary infection & COPD
Normal values for CEA
The typical upper limit for normal CEA values is
- Non-smokers-3.8 ng/ml
- Smokers-5.5 ng/ml
Utility of CEA
- Serum values of CEA have prognostic utility in patients with newly diagnosed CRC. If preoperative serum CEA > 5ng/ml, the patient has a worse prognosis, stage for stage, than with lower levels.
- Raised preoperative CEA levels that do not normalize after surgical resection implies the presence of persistent disease and the need for further investigations.
- Also serial assay of postoperative CEA levels must be performed for at least five years. A rising CEA that had normalized after surgery implies recurrent disease and must prompt follow-up radiological imaging.
- Patients with node-negative cancer and a high preoperative CEA must be considered higher than average risk for recurrence after surgery and this might influence the decision to administer adjuvant chemotherapy, especially if other risk factors like perforation or obstruction are present.