CEA is a glycoprotein normally produced only during early fetal life and rapid multiplication of epithelial cells, especially those of the digestive system. CEA also appears in the blood of chronic smokers. Less than 25% of patients with disease confined to the colon have elevated CEA. Sensitivity is increased with advancing tumor stage. CEA levels should be ordered only after malignancy has been confirmed. CEA levels typically return to normal within 4 " 6 weeks after surgical resection. Major role is in following patients for relapse after intended curative treatment. The American Society of Clinical Oncology recommends monitoring CEA levels every 2 " 3 months for at least 2 years in patients with stage II and III disease.
Normal values: <2.5 ng/mL in nonsmokers; <5 ng/mL in smokers.
Use
Monitoring colorectal cancer and selected other cancers such as medullary thyroid carcinoma, cancers of the rectum, lung, pancreas, stomach, and ovaries
May be useful in assessing the effectiveness of chemotherapy or radiation treatment
Diagnosis of malignant pleural effusion
Not useful in screening the general population for undetected cancers
Interpretation
Increased In
Cancer. There is a wide overlap in values between benign and malignant disease. Increased concentrations are suggestive but not diagnostic of cancer.
Seventy-five percent of patients with carcinoma of endodermal origin (colon, stomach, pancreas, lung) have CEA titers >2.5 ng/mL, and two thirds of these titers are >5 ng/mL. CEA is increased in about one third of patients with small cell carcinoma of the lung and in about two thirds with non " small cell carcinoma of the lung.
Fifty percent of patients with carcinoma of nonentodermal origin (especially cancer of the breast, head and neck, ovary) have CEA titers >2.5 ng/mL, and 50% of the titers are >5 ng/mL. Titers are increased in >50% of cases of breast cancer with metastases and 25% without metastases, but they are not associated with benign lesions.
Forty percent of patients with noncarcinomatous malignant disease have increased CEA concentrations, usually 2.5 " 5.0 ng/mL.
Increased in 90% of all patients with solid tissue tumors, especially with metastases to the liver or lung, but they are increased in only 50% of patients with local disease or only intra-abdominal metastases.
May be increased in effusion fluid due to these cancers. Active nonmalignant inflammatory diseases (especially of the GI tract [e.g., ulcerative colitis, regional enteritis, diverticulitis, peptic ulcer, chronic pancreatitis]) frequently have elevated concentrations that decline when the disease is in remission.
Liver disease (alcoholic, cirrhosis, chronic active hepatitis, obstructive jaundice) because metabolized by the liver.
Other disorders:
Renal failure
Fibrocystic disease of the breast
Limitations
When an abnormal level is found, the test should be repeated. If confirmed, the patient should undergo imaging of potential reoccurrence sites.
Same methodology should be used to monitor an individual patient. A significant change in plasma concentration is +25%.
After complete removal of colon cancer, CEA should fall to normal in 6 " 12 weeks. Failure to decline to normal concentrations postoperatively suggests incomplete resection. Immunohistochemistry of resected specimen is used to identify 20% of these cancers that do not express CEA for whom monitoring is misleading. In such cases, may use serum ALP and diagnostic imaging.
Prognosis is related to serum concentration at time of diagnosis (stage of disease and likelihood of recurrence). CEA concentrations <5 ng/mL before therapy suggest localized disease and a favorable prognosis, but a concentration >10 ng/mL suggests extensive disease and a poor prognosis; >80% of colon carcinoma patients with values >20 ng/mL have recurrence within 14 months after surgery. Plasma CEA >20 ng/mL correlates with tumor volume in breast and colon cancer and is usually associated with metastatic disease or with a few types of cancer (e.g., cancer of the colon or pancreas); however, metastases may occur with concentrations <20 ng/mL. Values <2.5 ng/mL do not rule out primary, metastatic, or recurrent cancer. Increased values in node-negative colon cancer may identify poorer-risk patients who may benefit from chemotherapy.
Patterns of CEA change during chemotherapy.
Uninterrupted increase indicating failure to respond.
Decrease indicating response to therapy.
Surge in CEA for weeks followed by a decrease indicating response.
Immediate, sustained decrease followed by an increase indicating lack of response to therapy.
Significant is 25 " 35% change from baseline of equal or increased values during the first 2 months of therapy.
Survival is significantly longer if titer decreases below this baseline.