The drawbacks of tumor markers
Early on in the search for tumor markers, the hope was that someday all cancers could be detected early with a blood test. 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 an 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.
- Because cancer is many different diseases, no single tumor marker can be used to look for all types of 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.
Last Medical Review: 10/30/2013
Last Revised: 10/30/2013