Prostate-specific antigen (PSA) is a
substance produced by the prostate
gland. Elevated PSA levels may indicate
prostate cancer or a noncancerous
condition such as prostatitis or an
enlarged prostate.
Most men have PSA levels under four (ng/mL)
and this has traditionally been used as
the cutoff for concern about risk of
prostate cancer. Men with prostate
cancer often have PSA levels higher than
four, although cancer is a possibility
at any PSA level. According to published
reports, men who have a prostate gland
that feels normal on examination and a
PSA less than four have a 15% chance of
having prostate cancer. Those with a PSA
between four and 10 have a 25% chance of
having prostate cancer and if the PSA is
higher than 10, the risk increases to
67%.
In the past, most experts viewed PSA
levels less than 4 ng/mL as normal. Due
to the findings from more recent
studies, some recommend lowering the
cutoff levels that determine if a PSA
value is normal or elevated. Some
researchers encourage using less than
2.5 or 3 ng/mL as a cutoff for normal
values, particularly in younger
patients. Younger patients tend to have
smaller prostates and lower PSA values,
so any elevation of the PSA in younger
men above 2.5 ng/mL is a cause for
concern.
Just as important as the PSA number
is the trend of that number (whether it
is going up, how quickly, and over what
period of time). It is important to
understand that the PSA test is not
perfect. Most men with elevated PSA
levels have noncancerous prostate
enlargement, which is a normal part of
aging. Conversely, low levels of PSA in
the bloodstream do not rule out the
possibility of prostate cancer. However,
most cases of early prostate cancer are
found by a PSA blood test.
How Is The PSA
Screening Test Done?
The test involves drawing blood,
usually from the arm. The results are
usually sent to a laboratory and most
often come back within several days.
When Should I Have
My PSA Levels Tested?
PSA blood tests and digital rectal
exams should be done every year for men
beginning at age 50, and earlier (age
40) for African American men and men
with a family history of prostate
cancer.
If your doctor is concerned that you
might have prostate cancer based on
either your PSA level or a rectal exam,
a biopsy (a lab testing of a small
amount of tissue from the prostate) will
be this next step This is the only way
to positively identify the presence of
cancer.
What Does an
Elevated PSA Level Mean?
Elevated PSA levels may indicate
prostate cancer or a noncancerous
condition such as prostatitis or an
enlarged prostate.
Your PSA level can also be affected
by other factors:
- Age. Your PSA will normally go
up slowly as you age, even if you
have no prostate problems.
- Medications. Some medicines may
affect blood PSA levels. Tell your
healthcare provider if you are
taking finasteride (Proscar or
Propecia) or dutasteride (Avodart).
These drugs may falsely lower PSA
levels typically by half of what it
would normally be.
If your PSA level is high, your
doctor may recommend that you get a
prostate biopsy to determine if you have
cancer.
Alternative PSA
Testing
There are some new PSA tests that may
help you and your health care provider
determine if you need a biopsy. You
should know that doctors do not always
agree on how to use or analyze the
results of these additional tests.
-
Percent-free PSA.
PSA takes two major forms in the
blood. One is attached, our bound,
to blood proteins and the other
circulates freely. The percent-free
PSA test indicates how much PSA
circulates free compared to the
total PSA level. The percentage of
free PSA is lower in men who have
prostate cancer than in men who do
not. Studies show that if your PSA
results are in the borderline range
(4 to 10), a low percent-free PSA
(less than 10%) means that your
likelihood of having prostate cancer
is about 50% and that you should
probably have a biopsy.
Many doctors recommend biopsies
for men whose percent-free PSA is 20
or less.
-
PSA velocity. The
PSA velocity is not a separate test.
Rather, it is the change in PSA
levels over time. Even when the
total PSA value isn't higher than 4,
a high PSA velocity (an increase
greater than 0.75 ng/mL in one year)
suggests that cancer may be present
and a biopsy should be considered.
Using the PSA Blood
Test After Prostate Cancer Diagnosis
Although the PSA test is used mainly
to screen for prostate cancer, it is
valuable in other situations:
- To guide treatment. Along with a
doctor's examination and tumor
grade, the PSA test can help
determine how advanced a prostate
cancer is. This may affect treatment
options.
- To determine treatment success.
After surgery or radiation, the PSA
level can be monitored to help
determine if treatment was
successful. PSA levels normally fall
to very low levels if the treatment
removed or destroyed all of the
cancer cells. A rising PSA level can
mean that prostate cancer cells are
present and your cancer has come
back.
If you choose a "watchful waiting"
approach to treatment, the PSA level can
help determine if the disease is
progressing and if active treatment
should be considered.
During hormonal therapy, the PSA
level can help indicate how well the
treatment is working or when it may be
time to try another treatment.
|