Generality
The carcino-embryonic antigen ( CEA ) is a protein that can be produced in large quantities by the cells of many forms of cancer : colorectal, thyroid, lung, breast, liver, pancreas, stomach and ovaries.
Consequently, CEA is used as a marker for the initial typing of the neoplastic process and to monitor the occurrence of recurrences.
The value of the carcinoembryonic antigen is higher in the presence of widespread neoplastic diseases. However, it should be borne in mind that the value may also rise due to non-tumor diseases, such as hepatitis, intestinal polyposis, colitis, emphysema and pneumonia. Furthermore, in smokers, this parameter is usually higher than those who do not smoke.
What's this
The carcinoembryonic antigen or more simply CEA (acronym of the English Carcino-Embryonic Antigen) is a glycoprotein with an approximate molecular weight of 210, 000 daltons. It is mainly produced by the fetal cells of the digestive tract, liver and pancreas, during the first two trimesters of gestation, while after birth it is very small.
It has also been seen that the carcinoembryonic antigen manifests a different molecular specificity, therefore immunological, depending on the tissues in which it is synthesized, due to variations in the glucidic component of the molecule.
More than a single macromolecule, we are therefore talking about a pool of heterogeneous molecules.
In adults, very small amounts of carcino-embryonic antigen are secreted by colon cells, lung parenchyma and breast tissue during lactation. Its particularly reduced blood level increases in numerous morbid conditions, both neoplastic and non-neoplastic.
Why do you measure
The search for carcino-embryonic antigen serves to determine its presence in the blood . The plasma concentration of this glycoprotein is in fact considered a tumor marker, as its presence is well correlated with some neoplastic diseases.
CEA is the specific marker of colorectal malignancy .
It is used above all to detect early recurrences (ie parts of the neoplasm that have recurred after a first treatment or surgery) and the presence of metastases .
In particular, the determination of the CEA is indicated in the following cases:
- Monitoring of tumor progression of colorectal cancer ;
- Differential diagnosis of liver neoplasms ;
- Post-operative control and determination of metastases and recurrences of breast and lung cancer .
The test of carcino-embryonic antigen is not useful, however, as a screening test.
However, it should be considered that its blood level may also increase in many non-neoplastic chronic diseases.
Increases in its value can be found during:
- Hepatopathies (including alcoholic cirrhosis);
- pancreatitis;
- Inflammatory bowel diseases;
- Diverticulitis;
- Polyposis of the colon;
- lung disease;
- Chronic renal failure.
The CEA also increases moderately with age.
Normal values
The carcinoembryonic antigen was first detected in 1965 by Gold and Freedman, during the examination of cell membranes of neoplastic cells in patients with adenocarcinoma of the colon.
CEA normal plasma concentration ranges from 0 to 2.5 - 3 ng / ml.
CEA Alto - Causes
As anticipated, high levels of carcinoembryonic antigen were found, as well as in colorectal tumors (70-90% of patients with malignant neoplasms of the large intestine), also in various other malignant and benign pathologies.
Benign diseases
Benign pathologies are for example:
- Pancreatitis;
- Bronchitis;
- Pulmonary emphysema;
- Gastritis;
- Gastric peptic ulcer;
- Liver cirrhosis:
- Uremic states;
- Benign jaundices;
- Crohn's disease;
- Ulcerative colitis;
- Diverticulosis.
The values of CEA also increase in a non-pathological condition which is rather widespread, which is that of the avid smoking. Equally widespread is a benign neoplastic condition known as colon polyposis; also in this case, the levels of carcinoembryonic antigen tend to be higher than the norm.
tumors
Unfortunately, there are no threshold values of CEA that differentiate malignant pathologies from benign ones, even if in general in the latter case the increases are rare or in any case limited (below 3 µg / ml). This poor specificity and sensitivity of the carcinoembryonic antigen prevents its use as a screening method for the early recognition of neoplastic diseases.
The CEA finds its most frequent application in colon cancer, in particular to monitor the response of patients undergoing surgical or other therapy, as well as a marker of possible relapses. Particular attention is therefore paid to monitoring the preoperative levels of CEA, because they correlate with the risk of neoplastic recurrence after resection of the primary tumor.
Moreover, in the post-operative period the levels of carcinoembryonic antigen are periodically monitored, since sensitive elevations of its levels are an early indicator of metastasis, which lights up already several weeks before the clinical and instrumental methods are able to detect them.
Another malignant pathology associated with a significant increase in carcinoembryonic antigen levels is pancreatic cancer, much rarer than the colon, but much more aggressive.
In conclusion, therefore, the carcino-embryonic antigen is not specific for any type of neoplasia, even if values higher than 20 µg / ml (20 mcg / ml) are significantly correlated with metastasis and / or primary carcinoma of the pancreas or colon -retto. Tendentially lower increases in CEA levels can be recorded in lung, gastric, ovarian, uterine and hepatic, mammary and renal carcinomas, as well as in leukemias, lymphomas and sarcomas.
CEA Basso - Causes
The carcino-embryonic antigen decreases in relation to the response to cancer treatment.
However, it is important to remember that negative values do not exclude the presence of a neoplasm. For this reason, the clinical significance of the test must be correlated to anamnestic, objective, instrumental and laboratory findings.
How to measure it
The carcino-embryonic antigen is measured by blood tests. These are repeated several times during the monitoring or treatment of the disease. Occasionally, the sample to search for CEA can be taken from other body fluids, such as peritoneal, pleural and cerebrospinal fluid (CSF).
Preparation
If the blood test also includes other tests, such as the evaluation of blood glucose or the cholesterol dosage, a fast of at least 8-10 hours must be observed before the collection.
Interpretation of Results
In general, particularly high CEA values are associated with colorectal cancer, but also with breast, stomach, lung, cervical and ovarian cancers.
Monitoring of therapy and cancer relapses
- When the concentration of carcinoembryonic antigen is initially high and subsequently decreases to normal after therapy, it means that the tumor has been successfully treated.
- A constant increase in CEA concentration is often the first sign of disease recurrence.
- It should be considered, however, that not all types of cancer produce carcinoembryonic antigen, it is possible to have cancer with normal values of carcino-embryonic antigen. If the tumor does not produce CEA, then the test is not useful in the monitoring program.
Prognosis and / or staging of neoplastic disease
In the case of tumors of limited size or in the initial stage, normal or low concentrations of CEA are often recorded. People with an extended tumor, at an advanced stage, or a widespread cancer in the body, have more common concentrations of high carcino-embryonic antigen.
Determination of the presence of metastases
If CEA is present in a body fluid that is not blood, it is likely that the tumor has spread to that area of the body. For example, the finding of the carcinoembionary antigen in the cerebrospinal fluid can be a sign of metastasis to the central nervous system.
