$Unique_ID{BRK00874}
$Pretitle{Special Procedures and Laboratory Tests}
$Title{Is There a Substance Known as a "Tumor Marker"?}
$Subject{cancer tumor markers}
$Volume{P}
$Log{}

Copyright (c) 1991   Tribune Media Services, Inc.


Is There a Substance Known as a "Tumor Marker"?


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QUESTION:  Is there a substance known as a "tumor marker"?  I am intrigued by
the idea and would like to know how they might work.

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ANSWER:  Researchers had once hoped to find that tumor cells produced certain
unique substances not made by normal cells.  If these substances could be
detected in the blood or urine with a simple test, mass screening would be
possible to diagnose cancerous tumors in their earliest stages,  when
treatment could be most effective.
     Unfortunately, such clearly defined markers have not been found.
Although some tumor cells do produce substances, other cells or certain
conditions also cause these same substances to be present.  For instance,
carcinoembryonic antigen (CEA) was once thought to be a marker for colon
cancer, but it's also present with cancer of the lung, breast, ovary, and
pancreas.  And, the levels of CEA are elevated in heavy smokers and patients
with inflammatory bowel or liver disease, so it's not useful for screening
large numbers of people for these types of cancer.
     What CEA and other tumor markers can do, however, is to help doctors
establish a specific diagnosis.  The presence and amounts of a tumor marker
can also be used to follow the response of a tumor to therapy and to detect
the occurrence of metastases (the spread of cancer cells to other locations in
the body from the original tumor site).
     Tumor markers can also be helpful when screening a high-risk population
for a certain type of cancer.  Because those persons are more likely to have a
certain type of cancer, the presence of the tumor marker is a more accurate
indication that cancer cells exist.
     For instance, measuring levels of alpha-fetoprotein (AFP) in the general
population isn't a very accurate way to detect early liver cancer.  But
measuring AFP in patients with cirrhosis of the liver, a group in which the
prevalence of liver cancer is 25 percent, is a useful tool.
ÿ
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The material contained here is "FOR INFORMATION ONLY" and should not replace 
the counsel and advice of your personal physician.  Promptly consulting your 
doctor is the best path to a quick and successful resolution of any medical 
problem.
