Prostate Cancer
Screening
DRE
A digital rectal examination
(DRE) is a quick and safe screening technique in which a
doctor inserts a gloved, lubricated finger into the rectum
to feel the size and shape of the prostate (See picture
below). The prostate should feel soft, smooth, and even.
The doctor examines for lumps or hard, irregular areas of
the prostate that may indicate the presence of prostate
cancer. The entire prostate cannot be felt during a DRE,
but most of it can be examined, including the area where
most prostate cancers are found.
When a tumor is small and
located only within the prostate, it is often not detected
during a DRE. However, if an abnormality is found during
the DRE, the new ACS guidelines suggest a prostate biopsy,
even if the PSA is normal.
Cancer cells in prostate
gland
Prostate-specific Antigen
(PSA)
Prostate-specific antigen
(PSA) is a substance produced by both normal and cancerous
prostate cells. When prostate cancer grows or when other
prostate diseases are present, the amount of PSA in the
blood often increases.
A PSA test is generally
said to be in the normal range when it is reported to be
between 0 and 4 nanograms per milliliter, sometimes abbreviated
as ng/mL on the lab report.
If the results are greater
than 4 ng/mL, your physician may suggest a biopsy, which
is the only test available to diagnose prostate cancer.
Guidelines published in
2005 by the National Comprehensive Cancer Network (NCCN)
suggest that the threshold for consideration of a biopsy
should be lower. The NCCN guidelines now recommend consideration
of biopsies for men with PSA levels in the range of 2.5
to 4.0 ng/mL.1
It may also be useful to
keep track of how your PSA level changes over a period of
time. If your PSA level is rising your physician may suggest
a biopsy.
PSA test results can be
confusing and do not mean that cancer is present. Certain
other conditions, such as benign prostatic hypertrophy (also
called BPH - a type of noncancerous prostate enlargement)
and prostatitis (inflammation of the prostate), may cause
an abnormal PSA result.
Additional PSA Tests
Because borderline PSA tests
can be confusing, your physician may advise you to consider
having one or more of the newer PSA tests. These are described
below:
Percent Free-PSA Ratio
Percent free-PSA ratio is
a blood test that measures how much PSA circulates by itself
(unbound) in the blood and how much is bound together with
other blood proteins. If PSA results are borderline and
percent free-PSA ratio is low (25% or less), then prostate
cancer is more likely to be present. If this is the case,
a biopsy may be needed.
If the results of the percent
free-PSA ratio are greater than 25%, even with a borderline
PSA, you may be able to avoid a biopsy.
Complexed PSA (cPSA) is
another test that measures PSA bound to a substance called
alpha-1-antichymotrypsin.
The Age Factor
Another way of looking at
PSA involves age-specific PSA reference ranges. PSA levels
increase with age; therefore, higher PSA levels are normally
seen in older men more often than in younger men, even without
cancer. An age-specific PSA reference range compares the
results of men in the same age group. If a man’s PSA levels
are high compared to his own age group, then there is a
greater chance that prostate cancer could be present. In
older men with borderline PSA results, this comparison can
be more confusing than useful. As a result, age-specific
PSA reference ranges are not routinely done.
PSA Density
If you have had your PSA
measured and also have had a transrectal ultrasound (TRUS),
then PSA density (PSAD) can be determined. To calculate
your PSAD, your physician will divide the PSA by the size,
or volume, of the prostate (determined from the TRUS). There
is a greater chance that prostate cancer is present with
a high PSAD.
PSA Velocity
Finally, PSA velocity shows
how quickly the PSA level rises over a period of time. Two
or more PSA tests are required, often over several months
of time. Although PSA velocity may be useful in helping
your doctor better interpret borderline PSA results, it
is not really used to diagnose prostate cancer. Instead,
it is used more as a tool to keep track of how your PSA
levels compare over a period of time.
PSA often rises as part
of the natural aging process; an increase in the PSA from
time to time does not necessarily indicate that prostate
cancer is present. On the other hand, if PSA increases too
quickly (as determined by your physician), prostate cancer
is a possibility.
PSA-DT
If you have been diagnosed
with prostate cancer, another factor your doctor may consider
is PSA doubling time (PSA-DT), which is the time it takes
your measured blood PSA levels to double. Generally, a shorter
PSA-DT indicates that the prognosis of your prostate cancer
may be worsening.
Newer PSA tests can be useful,
but they are still too new for physicians to agree on when
and how they should be used. If your PSA is borderline or
abnormal, your doctor can help you determine which tests,
if any, are right for you. A high PSA doesn’t necessarily
mean that prostate cancer is present, and a low or normal
PSA doesn’t always mean that prostate cancer isn’t present.
In other words, the PSA test may provide false results.
Therefore, it is used along with the results of the DRE
to provide more accurate screening.
TRUS
If your PSA test results
are borderline high, but your DRE results are normal, then
your doctor may recommend a transrectal ultrasound (TRUS).
During TRUS, a small probe is placed in recturn. This procedure
causes little discomfort.
As illustrated below, this
is a procedure that uses sound waves to create a picture
of the prostate, which can be used to help identify abnormal
areas requiring a biopsy. If the results of the TRUS are
normal, you may be able to wait and repeat the PSA test
a few months later and have a biopsy then if needed.
Ultrasound of the prostate
A transrectal ultrasound of the prostate.
How Is Prostate Cancer Detected?
The American Cancer Society
(ACS) has developed guidelines to help doctors detect prostate
cancer during its early stages. The ACS has recently revised
these guidelines to reflect new scientific literature. The
guidelines recognize that prostate cancer screening, including
a digital rectal examination (DRE) and a test to measure
prostate-specific antigen (PSA) in the blood, should be
offered yearly to the general male population 50 years of
age and older.2
In addition, males at increased
risk for developing prostate cancer, such as men with a
first-degree relative (father, brother, or son) affected
by the disease or those of African-American descent, should
consider annual screenings beginning at age 45. Men at even
higher risk because they have several first-degree relatives
who had prostate cancer at an early age should begin annual
screenings at age 40.2
There are some instances
in which prostate cancer screening may not be recommended.
Because prostate cancer can be a slow-growing cancer, a
man with a less than 10-year life expectancy would most
likely die of some other illness, and, therefore, is not
very likely to benefit from prostate cancer screening and
treatment. For this reason, the new ACS guidelines include
a statement for patients explaining the risks and benefits
of prostate cancer screening. These guidelines can be found
on the Internet at: www.cancer.org or by calling the American
Cancer Society at 1-800-ACS-2345.
You and your physician can
discuss the ACS guidelines together and determine if screening
is right for you, and, if so, when you should begin.
References
1. Prostate Cancer Early
Detection Clinical Practice Guidelines in Oncology. JNCCN,
2005. Available at: www.nccn.org. Accessed July 11, 2005.
2. American Cancer Society.
Detailed Guide: Prostate Cancer. 2005. Available at: http://www.cancer.org/docroot/CRI/CRI_2_3x.asp.
Accessed July 11, 2005.
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The information on this page has been extracted from http://www.prostateinfo.com/patients/diagnosis/
