The Chinese name for CEA is carcinoembryonic antigen, and by that name you know it is associated with two things, cancer and embryos. It is significantly elevated in certain cancers and embryonic tissues. Which cancers are they? The most common one is gastrointestinal cancer, so the question is, is a high CEA necessarily cancer? Or is CEA always elevated in cancer? The answer is not necessarily either. To understand why, it is important to understand CEA first. CEA is a blood tumor marker, which is a powerful basis for determining the diagnosis, efficacy, prognosis and selection of protocol for gastrointestinal cancers, but it can only be used as an aid. CEA can be produced by cancer cells and detected in the blood, but elevated CEA can be due to multiple causes. For example, pregnancy, smoking and reproductive tumors may cause an elevation; or there may be a single elevation due to different testing instruments or reagents.i The specific situation should be determined clinically. Therefore, elevated CEA does not necessarily mean that you have cancer. Since we test CEA in blood, CEA produced by cancer cells has to go through a long pathway to appear in blood, so not every cancer patient has high CEA, thus it is common to see some gastrointestinal cancer patients clinically whose CEA has been normal and has not changed significantly before and after surgery. If you find a mildly elevated CEA in a certain physical examination, there is no need to panic too much. If the value is maintained at the critical level of the upper reference value after the review, it is not significant. However, the following types of cases should be paid special attention to: 1, is a single examination is particularly obvious, several times the upper limit of the normal value. 2. Repeated examinations with dynamically and continuously elevated values. 3. Individuals with family history of gastrointestinal cancer. For a patient with gastrointestinal cancer, CEA tumor marker can determine the treatment effect and prognosis. The level of CEA is closely related to the malignancy, metastasis and recurrence of the tumor. In clinical practice, the CEA level after the initial treatment has achieved efficacy is used as the specific “individual reference value” to judge the efficacy according to its dynamic change. If the CEA level decreases to within the reference value or decreases by more than 95%, it indicates that the treatment is effective; if it decreases but still continues to be above the reference value, it indicates residual tumor and/or metastasis; if it decreases to within the reference value and then increases again after a period of time, it indicates recurrence or metastasis. When testing CEA, try to choose the same hospital or the same clinical laboratory. Because test results from different hospitals often lack comparability, it is important to choose the same hospital for long-term follow-up CEA monitoring so that doctors can make more accurate judgments.