In a digital rectal examination, the
physician inserts a lubricated, gloved finger
into the patient's rectum, reaching in to feel
the surface of the prostate gland. Healthy
prostate tissue is soft, like the fleshy
tissue of the hand where the thumb joins the
palm. Malignant tissue is firm, hard, often
asymmetrical or stony, like the bridge of the
nose. The test is subjective, however, and
relies on the physician's ability to interpret
what he or she feels. Only larger tumors can
be felt; as many as one-third of patients
subsequently diagnosed with prostate cancer
actually will still have a normal DRE.
If the physician finds any conditions
suggesting the presence of a tumor on the
prostate, he or she likely will want to
perform an additional blood screening test.
Called the prostate specific antigen or PSA
test, this procedure can give information
about whether prostate cancer is present and,
if so, in what amount. It also may suggest
whether the cancer is likely to have spread.
Prostate specific antigen is a substance
produced only by the cells of the prostate
capsule (membrane covering the prostate) and
periurethral glands. The test measures the
amount of PSA present in the blood. An
elevated or rising PSA level can indicate the
existence of prostate cancer.
PSA is measured in nanograms per milliliter
(ng/ml) of blood. A PSA of 4 ng/ml or lower is
normal and a PSA above 10 ng/ml suggests the
presence of cancer; the range 4-10 ng/ml is a
gray area, and readings in this range are
considered inconclusive.
Additionally, PSA levels also are related
in part to the size of the prostate, and
patients with benign prostatic hyperplasia (BPH)
or a prostate inflamed by prostatitis also
produce elevated levels of PSA. For these
reasons, scientists have modified the PSA
testing process by developing several new
PSA-based refinements:
PSA Velocity (PSAV)--Researchers have
studied the rate of change in PSA over time
in men whose medical outcomes were known.
This rate of change in PSA is known as PSA
velocity (PSAV). A rate of change in PSA
velocity of 0.75 ng/ml/yr or higher has been
conclusively linked to clinically
significant prostate cancer. Therefore, a
man with a PSA in the gray area of 4-10 ng/ml,
and who is found to have a PSAV of 0.75 ng/ml/yr,
may have a cancerous prostate condition.
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Prostatic
Acid Phosphatase (PAP) Test
Prostatic acid phosphatase is an enzyme
produced by several types of tissue,
including normal prostate tissue. Its
production increases as prostate disease
progresses. In conjunction with other
testing procedures, PAP testing has been
used to detect and monitor advanced prostate
cancer. By itself, it is less useful as a
diagnostic tool than PSA testing.
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Prostate Biopsy
Once the physician has diagnosed a likely
cancerous prostate condition by means of a
digital rectal exam or a PSA test, he or she
may want to perform other tests to determine
the type of cancer, its location and stage
of development. One of these is a prostate
biopsy.
Biopsies use a needle similar in size to
those used to draw blood or administer
injections to extract a sample of tissue
from the suspected cancer site. This is
analyzed by a pathologist (a physician who
is a specialist in diseases) to confirm the
presence of cancer and determine its type.
A patient undergoing a prostate biopsy is
advised to abstain from alcohol, aspirin or
non-steroid anti-inflammatory drugs for one
week before the procedure. He also is
required to have a Fleet enema and take an
oral antibiotic (usually ciprofloxacin) for
a day before and two days after the biopsy.
The biopsy is performed with the patient
lying on his side. A biopsy needle may be
inserted through the perineum into the
tumor, or a probe, guided by a transrectal
ultrasound (TRUS) device, may be
inserted into the rectum, and a needle
projected into the tumor through a port in
the tip of the probe. A cell sample is then
extracted into a syringe and taken for
analysis by the pathologist. Samples may be
taken from several parts of the tumor.
While the biopsy is a valuable
conventional procedure, it can have risks
for the prostate cancer patient. It may
produce bleeding which is difficult to
control, or it may cause infection from
rectal bacteria.
Additionally,
doctors and researchers have noted that
biopsy of a cancerous tumor can cause
spreading or "seeding" of cancer
cells along the path or track made by the
biopsy needle. This could cause a cancerous
condition which had been confined solely to
the prostate capsule to spread into
surrounding tissues, making a serious health
concern even more problematical.
While cancer seeding from biopsy is
uncommon, patients and physicians should be
aware of these potential risks, have a clear
understanding of what information they want
to obtain from a biopsy, and what action
will be taken based upon that information.
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Prostate
Ultrasound
Transrectal ultrasound (TRUS) imaging is
commonly used to measure the size of the
prostate, and to detect and analyze
cancerous tumors. This procedure uses a
special probe inserted through the rectum to
project ultrasonic impulses against the
prostate. The results are viewed on a
monitor, enabling the physician and operator
to obtain a visual image of the gland,
surrounding tissue and tumors that may be
present. Not all cancers can be seen
ultrasonically, however, so as a screening
measure TRUS is most useful when performed
in conjunction with a digit rectal exam (DRE
Studies have shown that the combination of
TRUS and DRE together is more effective at
detecting prostate cancers than either
procedure performed alone.
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Gleason Score
Once the presence of a cancerous tumor
has been confirmed by biopsy, the
pathologist will evaluate its relative
malignancy and potential for metastasizing
(spreading). He or she will examine the
biopsy sample(s) under a microscope with an
eye toward finding cells or groups of cells
that are markedly different from healthy
tissue. The greater the disparity between
the healthy cells and those that are
malignant, the greater the likelihood that
the tumor is aggressive and apt to spread.
The usual method for expressing the results
of this analysis is the Gleason Grading
System.
Under the Gleason System, the pathologist
examines biopsy samples from two different
parts of the tumor and assigns them a grade
of 1 to 5 based on their degree of
differentiation (the amount by which they
differ from healthy tissue). The more
abnormal the tissue, the higher the score.
The results of these two samples are added
together to produce a Gleason Score of from
2 to 10. Gleason Scores of 2 to 4 are
considered well-differentiated, meaning the
tissue is not too different from normal; 5
to 7 are moderately differentiated; 8 to 10
are poorly differentiated. Higher scores
indicate aggressive tumors that are likely
to require aggressive treatment.
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Lymph
Nodes and Lymphadenectomy
Lymph nodes are round or oval bodies that
supply white blood cells to the circulatory
system. These cells, called lymphocytes,
typically remove bacteria and foreign
particles from the blood. But when cancer
cells invade the bloodstream, they can be
spread to other parts of the body.
When prostatic cancer spreads, it usually
migrates first to the lymph nodes in the
pelvis. The doctor can estimate the
likelihood of this spread on the basis of
the biopsy results, PSA tests and the size
of the tumor. He or she also may recommend
removing these nodes for microscopic
examination.
If it appears likely that the cancer has
spread, the doctor may recommend having them
surgically removed through an incision in
the lower abdomen. This procedure, called
surgical lymphadenectomy, can be done at the
same time that the cancerous prostate is
removed (radical prostatectomy). Because the
body has many lymph nodes, the loss of a few
in the pelvic region does not cause a
problem.
The doctor also may examine and remove
the nodes with a laparoscope, a miniature
telescopic device connected to a monitor.
This device is inserted through four small
incisions in the lower abdomen. Laparoscopic
lymphadenectomy requires less recovery time
in hospital for the patient than an open
lymphadenectomy. But because it constitutes
a second surgical procedure, the
desirability of performing this process must
be assessed relative to the need to remove
the prostate as well. If it appears that a
radical prostatectomy will be necessary, the
doctor and patient may elect to remove both
in a single operation.
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Computed
Tomographic (CT) Scan
Also known as a computer-assisted
tomography or "CAT" scan, the CT
scan is a type of X-ray procedure that gives
three-dimensional images of internal organs
or glands. It can be used to detect pelvic
lymph nodes enlarged by cancer, although
some authorities suggest its results are
insufficiently clear to generate useful
results. CT scans typically are used only
when tumors are large or associated with
high PSA levels.
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Bone Scan
A bone scan is a nuclear imaging
procedure that can detect the spread of
cancer to bones. It usually is prescribed in
cases where aggressive tumors and metastasis
are suspected. Normally, it is not used in
patients with small cancers and low PSA
levels.
PROSTATE
CANCER
Digital
Rectal Exam (DRE)