Carcinoembryonic antigen (CEA)
Why this test?
- For diagnosis and monitoring of malignant tumor treatment.
- To confirm the success of surgical treatment of malignant tumors.
- To evaluate the effectiveness of conservative therapy of malignant tumors.
- For early detection of cancer relapses during long-term follow-up after the end of treatment.
In what cases is it prescribed?
- If a tumor is suspected: large intestine, rectum, stomach, pancreas, mammary gland, lungs, ovaries, tumor metastasis to the liver and bones.
- When monitoring the therapy of malignant neoplasms.
- After surgery to remove a malignant tumor.
- In the process of long-term follow-up after the completion of cancer treatment.
Cancer embryonic antigen is a type of protein of normal tissues, which in a healthy person is produced in very small amounts in the cells of some internal organs. According to the chemical structure, REA is a combination of protein and carbohydrates (glycoprotein).
Its purpose in adults is unknown, and during the period of intrauterine development it is intensively synthesized in the organs of the gastrointestinal tract and performs important functions related to the stimulation of cell reproduction. REA is also detected in the tissues of the digestive organs and in adults, but in much smaller quantities.
Determination of the level of REA is used to diagnose a number of malignant tumors, primarily colon and rectal cancer. If normally the REA content is very low, then during the oncological process it increases sharply and can reach very high values. In this regard, it is classified as tissue markers of oncological diseases, or tumor markers.
However, an increase in REA is characteristic not only of a malignant process - its production can increase in various inflammatory, autoimmune and other benign diseases of internal organs. The name of this tumor marker - cancer embryonic antigen - partly reflects its biological nature, but to a greater extent those properties that are valuable for laboratory research. "Cancer" refers to its use to diagnose cancer. The definition "embryonic" is related to the physiological functions of the REA during the period of intrauterine development of a person. The word "antigen" indicates the possibility of its identification in biological environments with the help of immunochemical analysis (antigen-antibody binding), while in the body it does not show any antigenic properties.
REA analysis is used for early diagnosis, monitoring the course of the disease and monitoring the results of its treatment in some tumors, primarily if it is cancer of the large intestine and rectum - in these cases, the test has the highest sensitivity, which allows it to be used in primary diagnosis. In addition to tumors of the large intestine and rectum, REA can increase in stomach, pancreas, breast, lung, prostate, ovary, cancer metastases of various origins in the liver and bones, although the sensitivity of the method is significantly lower in these conditions.
In addition to the initial diagnosis of cancer, the REA test is used to monitor the results of its treatment. After a successful operation to remove all the tumor tissue, the REA level returns to normal within a maximum of two months. In the future, regular tests help monitor the patient's condition after treatment.
Detection of an elevated level of REA at an early stage makes it possible to detect a relapse of the disease in time. REA analysis is also used to monitor the effectiveness of therapy for malignant processes.
A decrease in the level of REA in the blood during the course of procedures or after it indicates a positive result of the treatment.
However, this test is not completely specific for tumors. REA can moderately increase in many diseases of internal organs of an inflammatory and other (benign) nature. Its concentration slightly increases in 20-50% of patients with benign diseases of the intestines, pancreas, liver and lungs, as well as in cirrhosis of the liver, chronic hepatitis, pancreatitis, ulcerative colitis, Crohn's disease, pneumonia, bronchitis, tuberculosis, emphysema, cystic fibrosis and autoimmune diseases.
The indicator increases when the disease worsens, but returns to normal when the condition improves. In the case of a malignant process, the level of REA increases steadily throughout the entire period of the disease. In addition, an increase in REA may not be associated with pathology, but, for example, with regular smoking and alcohol consumption.