Can you detect colon cancer in the blood?
Colon cancer is not a disease that can be diagnosed based on blood tests. On the contrary: the determination of blood values plays a rather subordinate role in colon cancer diagnostics.
Nonetheless, blood will be drawn from all patients suspected of having colon cancer. This has to do with the fact that the functionality of numerous organ systems can be checked. Some blood tests also provide information about how the colon cancer is developing.
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Can you detect colon cancer in the blood?
Colon cancer is not a diagnosis that can be made from specific blood tests. In order to be able to diagnose colon cancer with certainty, a colonoscopy must be performed.
During this colonoscopy, tissue samples are taken from the suspicious areas of the mucous membrane. These are examined under the microscope (histology). Colon cancer can only be reliably diagnosed on the basis of this microscopic assessment of the tissue samples obtained.
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What tumor markers are there for colon cancer?
There are so-called tumor markers for many tumor diseases. These are blood values that increase in certain tumor diseases.
The tumor marker for colon cancer is the so-called carcinoembryonic antigen, abbreviated as CEA. The CEA is not only a tumor marker in colon cancer but can also be used in tumors in the area of the pancreas (pancreatic carcinoma), the lungs (bronchial carcinoma), the breast (breast carcinoma), the stomach (gastric carcinoma), the ovaries (ovarian carcinoma) and the thyroid gland (medullary carcinoma) Thyroid cancer).
Certain benign diseases can also have an elevated CEA value. For example, with liver diseases such as cirrhosis or hepatitis as well as with chronic inflammatory bowel diseases. The value can also be slightly higher with chronic alcohol consumption or with smokers.
You can find additional information on this at: Tumor markers
How safe are they?
The name tumor marker is somewhat misleading for the medical layperson.
A tumor marker is a blood test that can provide information about a specific tumor disease. However, tumor markers cannot be used to reliably diagnose a tumor disease. Rather, they play a crucial role in assessing the progression of the cancer after the diagnosis has been made. A drop in the tumor marker in the course of colon cancer therapy indicates a therapeutic success. A renewed rise in the tumor marker after successful therapy, however, indicates a recurrence of the tumor (relapse).
However, colon cancer can never be diagnosed on the basis of the tumor marker alone.
Which blood value constellations can indicate colon cancer?
An increased CEA level in the blood can indicate the presence of colon cancer.
However, the value alone is not sufficiently meaningful, as it can also be increased in numerous other diseases. In addition to the tumor marker, colon cancer can lead to anemia. This is the case when the tumor tissue has infiltrated the intestinal wall and small vessels are attacked by the tumor cells. This can lead to small oozing bleeding, but also larger bleeding.
Clinically, greater blood loss can be shown, for example, by the stool turning black (tarry stool). There are also tests that can detect small amounts of blood (occult blood) in your stool. Such bleeding can be seen in the blood based on the red blood cells or the hemoglobin value. If this value is lowered, one speaks of anemia (anemia). Such anemia can be an indicator of colon cancer. However, it is completely unspecific as it can occur in a wide variety of diseases.
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Can you have colon cancer despite having good blood values?
Unfortunately, many cancers do not show up in the blood. This makes the diagnosis difficult in some cases and means that some cancers are diagnosed late. Very few cancers show up on the basis of certain blood values. There are also many patients with colon cancer who have completely normal blood values. An increase in the CEA value is common, but not a safe criterion.
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