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Cancer Related

Tumor markers are substances that can be found in the body (usually in the blood or urine) when cancer is present. Along with other tests, tumor markers can be used to help show if cancer is present, to determine the type of cancer, and in some cases to help show if treatment is working.

The classic tumor marker is a protein that can be found in the blood in higher than normal amounts when a certain type of cancer is present, but not all tumor markers are like that. Some are found in urine or other body fluid, and others are found in tumors and other tissue. They may be made by the cancer cells themselves, or by the body in response to cancer or other conditions. Most tumor markers are proteins, but some newer markers are genes or other substances.

There are many different tumor markers. Some are linked only to one type of cancer, while others can be found in many types of cancer.

Tumor markers alone are rarely enough to show that cancer is present. Most tumor markers can be made by normal cells as well as by cancer cells. Sometimes, non-cancerous diseases can also cause levels of certain tumor markers to be higher than normal. And not every person with cancer may have higher levels of a tumor marker.

This is why most doctors use only certain tumor markers. When a doctor looks at the level of a tumor marker, he or she will consider it along with the patient’s history, physical exam, and other lab tests or imaging tests.

Drawbacks of tumor markers

 A simple blood test that could find cancers in their earliest stages could prevent the deaths of millions of people. But very few tumor markers are useful for finding cancer at a very early stage. There are a few reasons for this:

  • Almost everyone has a small amount of these markers in their blood, so it’s very hard to spot early cancers by using these tests.
  • The levels of these markers tend to get higher than normal only when there’s a large amount of cancer present.
  • Some people with cancer never have high tumor marker levels.
  • Even when levels of these markers are high, it doesn’t always mean cancer is present. For example, the level of the tumor marker CA 125 can be high in women with gynecologic conditions other than ovarian cancer.

These are the reasons why, today, tumor markers are used mainly in patients who have already been diagnosed with cancer to watch their response to treatment or look for the return of cancer after treatment