Tumor Marker:- Part 11 – Carcinoembryonic Antigen (CEA)
Sample
- This test is done on the serum of the patient.
- The serum is stable for 24 hours at 2 to 8 °C.
- For a long time, freeze the serum at -20 °C.
- Some methods may use plasma.
- For plasma use EDTA 2mg/mL.
- No special preparation is needed.
- This test can be done on peritoneal fluid and CSF if it is raised to indicate tumor metastasis.
Precautions
- Smokers have a higher CEA level.
- Keep in mind about the benign conditions like colitis, diverticulitis, and cholecystitis give raised CEA level.
- Also, liver diseases give raised the CEA level.
Purpose of the test (Indications)
- CEA is a tumor marker for:
- Colorectal carcinoma.
- Gastrointestinal carcinoma.
- Lungs malignancies.
- Breast cancers.
- This is a tumor marker and used to find the extent of disease in patients particularly gastrointestinal cancers.
- This may be used in breast cancers.
- This test is used to monitor the disease and treatment.
Pathophysiology
- CEA was discovered in 1965 by the Gold and Freeman.
- This was found in the serum of a patient with colorectal carcinoma.
- Thus this CEA antigen was considered the indicator of colorectal cancers.
- Later on found in the other various tumors like breast, stomach, pancreas and hepatobiliary tumors, and sarcomas.
- This was also found in benign conditions like ulcerative colitis, cirrhosis, and diverticulitis.
- Chronic smokers also have raised the level of CEA.
- The tissue which is found in embryonic tissue is called carcinoembryonic antigen (CEA).
- CEA is normally found in the fetal gut tissue.
- By the time of the birth detectable level of CEA disappears.
- There are about 10 genes located on the chromosomes 19 encode the CEA protein.
- This is a glycoprotein with a molecular weight of 150 to 300 k
- This was found in the serum of a patient with colorectal carcinoma.
- CEA is a tumor-associated, oncofetal antigen seen in embryonic and fetal tissue.
- CEA is a glycoprotein which normally occurs in fetal gut tissue.
- CEA is increased by 30% of colorectal, lung, liver, pancreas, breast, head and neck, urinary bladder, cervix, prostate, and medullary thyroid carcinoma.
- This is more specific for colorectal carcinoma.
- In a patient with colorectal carcinoma, its level correlates with the tumor stage, tumor grade, and tumor site.
- Well-differentiated tumors produce more CEA than poorly differentiated tumors.
- CEA is less commonly increased in lymphoma, leukemia, and malignant melanoma.
- CEA also has been seen in an HIV-positive patient with P.C.carinii, a heavy smoker, and inflammatory bowel disease.
- This is metabolized in the liver so in liver disease is increased.
- Its median value is higher for smokers than non-smokers.
- It is useful for monitoring GIT cancer especially colorectal carcinoma.
- CEA is increased 60 to 90% of metastasis of lung cancer.
- If the CEA level increase after surgery than the baseline is indicative of recurrence of the tumor.
- Patient with high preoperative concentration has a poor prognosis than those who have low values.
Drawbacks of CEA
- CEA can be detected in benign and malignant conditions.
- CEA is not raised in all colorectal cancers. Therefore not a reliable screening test.
- Its use is limited to know the prognosis and monitoring the tumor response to antineoplastic therapy in patients with cancer.
- CEA is helpful in patients with breast and gastrointestinal malignancies.
Normal
Source 1
Nonsmoker
- 99% = <5 ng/mL
- 1% = 5.1 to 10 ng/mL
- 0% = >10 ng/mL
Smoker
- 95% = <5.0 ng/mL
- 4% = 5.1 to 10 ng/mL
- 1% = >10 ng/mL
Source 2
- Adult (Non Smoker) = < 2.5 ng/ml
- Adult (Smoker) = < 5 ng/ml
Raised in benign conditions:
- in cirrhosis (45%).
- Pulmonary emphysema (30%).
- Benign breast disease (15%).
- Ulcerative colitis (15%).
- Rectal polyp (5%).
- pancreatitis.
- smoking.
- Inflammation.
- Hypothyroidism.
- Inflammatory bowel disease.
- Peptic ulcer.
Raised in malignant condition:
- colorectal cancer (70%).
- In Duke’s stage A 28%.
- In Duke’s stage B 45%.
- Lung (45%).
- breast cancer (40%).
- Gastric carcinoma (50%).
- Giant cell carcinoma of the thyroid.
- Pancreatic cancer (55%).
- Ovarian cancers (25%).
- Uterine carcinoma (40%).
Important facts of CEA in Colon Carcinoma:
- CEA level varies inversely with the grade, and well-differentiated tumor producing more CEA than poorly differentiated carcinoma.
- This is not a reliable screening test for cancer. This is good to monitor the recurrence of colon cancer.
- Pretreatment CEA level is a good indicator of tumor burden and prognosis.
- The preoperative level of >5 ng/mL is a poor prognostic indicator.
- After surgery, it should come to a normal level.
- Persistently raised level after surgery indicates the presence of the disease and need further workup.
- patient with low or normal level has a limited disease than a high level indicating advanced disease and maybe with metastasis.
- Drastically low level after surgery indicates almost complete cure of the tumor.
- If there are raised levels 5 times of the normal, then laparotomy is positive in 90% of the cases.
- CEA is raised in only 25 % of cancer confined to the colon, 50 % positive nodes, and 75 % with distant metastasis.
- Left-sided cancers have more raised CEA than right-sided tumors.
- Bowel obstruction produces a higher level of CEA.
- In the case of liver diseases, it’s level is raised because it’s metabolized in the liver.
- Patient with a high level of preoperative CEA has a worse outcome than patient with low level.