A tumor marker
is a chemical produced by the body. When the body begins
to develop a tumor, either the body or the tumor will
begin to produce a chemical that is specific to a certain
type of cancer. Doctors can measure the volume of a
tumor marker and determine the tumor’s size. In
the case of prostate cancer, the tumor marker is prostate-specific
antigen or PSA. The prostate gland constantly produces
small amounts of PSA, some of which enters the blood
stream. When the prostate gland grows in size, the amount
of PSA in the blood stream increases. Doctors can use
the PSA test to measure the amount of prostate specific
antigen. If the PSA amount is high or the PSA velocity
is high, doctors may use other tests such as the digital
rectal exam or the prostate biopsy to search for prostate
cancer. Other benign conditions, such as benign prostatic
hyperplasia, however, may also account for an increase
in the amount of prostate-specific antigen.
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