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Prostate-Specific Antigen (PSA),
Complexed |
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Other PSA tests
that measure just the free or complexed portion are also
available.
The relative proportions of free and complexed PSA are thought
to be different in prostate cancer when compared with other
prostatic diseases. Men with cancer are thought to have a
smaller proportion of free PSA and more complexed PSA than men
with other benign prostatic diseases such as benign prostatic
hyperplasia (BPH) or prostatitis, which can also lead to
abnormal total PSA test results.
Free or complexed PSA tests are provided by some laboratories
usually in addition to the total PSA test. They have often been
used as reflex tests following a raised total PSA test result.
The results are then expressed as the percentage of free PSA
compared with the total amount of PSA detected. Any results
below a cut-off are thought to be suggestive of prostate cancer.
These free or complexed PSA tests are designed to be used when
the total PSA test result is marginally raised, and not in cases
where the total PSA test result is very high and suggestive of
advanced prostate cancer.
The introduction of free PSA (fPSA) testing has introduced a
greater level of specificity in identifying early prostate
cancer. In 1998, the FDA approved fPSA testing as a diagnostic
aid for men with total PSA values between 4.0-10.0 ng/mL. This
has often been the diagnostic gray zone for total PSA testing
and fPSA may aid in the stratification. In general, “At
any percent free PSA level, one could be a lot more reassured in
the man with the small prostate…if somebody has a really low
percent free PSA, 10 or 12, no matter how big or how small their
prostate is, then you worry. And if a patient has a really high
free PSA, say 30%, no matter how big or small his prostate is,
you can feel reassured.” (William Catalona, M.D.,
Urologist at Barnes Hosptial, Washington University, St. Louis)
But fPSA levels between 10-25% are another gray zone as the
table illustrates. Additional testing on the horizon includes
complexed PSA and human glandular kallikrein (hK2) to fPSA
ratio.
Probability of Prostate Cancer Based Upon Test Results (Modified
from Hybridech, Inc.)
|
Standard PSA |
Probability of cancer |
Percent free PSA |
Probability of cancer |
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0-2 ng/mL |
1% |
0-10% |
56% |
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2-4 ng/mL |
15% |
10-15% |
28% |
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4-10 ng/mL |
25% |
15-20% |
20% |
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>10 ng/mL |
>50% |
20-25% |
16% |
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>25% |
8%
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Prostate-Specific Antigen (PSA)
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The PSA test is a blood test
that is used to screen for the presence of prostate cancer.
Prostate specific antigen is a protein found in the fluid
portion of blood, called serum. PSA is specific to the prostate.
No other human tissue or body part can make it. PSA levels can
be measured in an individual's serum. With this information,
doctors are able to screen for prostate cancer. PSA is only
present in men. PSA is present in all normal prostate tissue.
The normal prostate cell holds onto most of the PSA. Very little
leaks into the bloodstream. The small amount that leaks out is
what is measured by the blood test. Prostate cancer cells
actually have less PSA in each cell. However, the cancer cell
tends to leak more PSA into the bloodstream. Knowing this fact,
experts developed a range of expected values in patients with a
normal prostate gland. The PSA value should be less than 4.0.
This number reflects the belief that most men, roughly 95%, with
normal prostate glands have a PSA value of 4.0 or less. (See
below for age-specific normal values.) Almost any condition that
affects the prostate can make the PSA rise.
The American Cancer Society and the American Urological
Association recommend that men over age 50 have a yearly PSA.
They should also have a rectal examination of the prostate.
High-risk groups should begin screening at age 40 to 45. Men
with a family history of the disease and African Americans fall
into this category
When
evaluating PSA results, the doctor must also take into account
the results of the rectal exam, the patient's age, previous PSA
results, and prostatic size. For example, findings on a rectal
exam must be looked into even if the PSA result is normal.
Recent studies have suggested that the 4.0 level may be too high
for younger men and too low for older men. Many researchers now
use the following levels rather than the 4.0 used in the past.
However, more time is needed to assure that these levels are
more accurate.
|
AGE |
NORMAL RANGE |
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40 to 50 |
0 to 2.5 |
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50 to 60 |
0 to 3.5 |
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60 to 70, |
0 to 4.5 |
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70 to 80 |
0 to 6.5 |
If the rectal exam is
normal then the following recommendations are suggested: PSA of
4 or less. If the PSA level has been measured for the first time
and is less than 4, repeat testing is recommended on a yearly
basis. (This number may be dependent on age. See above for
normal values). PSA between 4 and 10.
If the PSA level is greater than 4 but less than 10, a
diagnostic ultrasound of the prostate is recommended. If the
ultrasound shows no suspicious areas, the prostate can be
monitored through regular testing and exams.
Another option is to take random biopsies from various parts of
the prostate. If observation alone is used, the PSA should be
repeated in 4 to 6 months and no later than a year. If the
ultrasound shows a suspicious area, then biopsy of the area
needs to be performed. This can be done at the time of the
ultrasound. The patient will need to take antibiotics ahead of
time. PSA greater than 10. If the
PSA is greater than 10, diagnostic ultrasound of the prostate
with biopsies is the recommended course. If the ultrasound shows
no suspicious areas, then random biopsies of the prostate are
taken. If the ultrasound shows suspicious areas, then biopsies
of the areas along with random biopsies need to be done. If
previous PSA values are available, test results will be
evaluated differently. The PSA level almost always rises if
cancer is growing. Any PSA level that is rising is suspicious.
However, a high PSA level may not mean that cancer is present.
For example, a male with a stable PSA of 8 over a three-year
period (8,8,8) is probably at less risk than a male with a PSA
of 2, 4, and 6 over the same time frame. This is because the
second patient's rising levels suggest growth. This makes it
suspicious for cancer. If the first patient had a negative
biopsy when the first high PSA value occurred, there may be no
need to repeat the biopsies. If the PSA level jumped to 10 or 15
for no apparent reason, then repeat ultrasound and biopsies
would be called for. Recent studies suggest that either a 20%
rise or a measurable rise of 0.75 in PSA in one year should
prompt a closer look. Ultrasound and biopsy may be needed.
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Prostate-Specific Antigen (PSA),
Free/Total Ratio |
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C E A |
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Colorectal, pancreas, lung, breast,
stomach, thyroid, female genital cancers.
In case
of cancer, higher rates will be reported in the following carcinomas:
pancreas (65-90% of the cases with very high rates);
lungs (52-77%);
breast (50%);
stomach;
thyroid (high rates);
and female genital cancers (25-40%). |
PSA represents a major
indicator for the diagnosis and management of prostate cancer.
However, within the range of 4-10 ng/mL, in which 75% of men do
not have cancer, the PSA lacks specificity. At this range, 4 men
require a biopsy to identify 1 man with cancer.
Stenman et al studied this problem and reported in 1991 that men
with prostate cancer had more complexed prostate-specific
antigen (cPSA) than fPSA, in contrast to men with BPH. After the
development of an immunoassay, investigators demonstrated that
the ratio of free-to-total prostate-specific antigen (f/tPSA)
was lower in men with prostate cancer.
In the PSA range of 4-10, total prostate-specific antigen (tPSA)
segregates adequately between men with or without cancer. The f/tPSA
is more discriminatory.
A 7-institution study investigated 63 men with BPH, 30 men with
prostate cancer (prostate size >40 cm3), and 20 men with small
prostates. All of the PSA levels were 4-10 ng/mL. The median f/tPSA
proportion was 0.188 (in BPH), 0.159 (in prostate cancer
[prostate size >40 cm3]), and 0.092 (in small prostates).
This implies that prostate size is an important variable in
selecting a cutoff value for fPSA. For men whose prostates are
smaller than 40 cm3, a percent fPSA of 0.137 or lower is used to
detect 90% of the cancers, and 76% of the negative biopsy
findings can be eliminated. For men with prostates larger than
40 cm3, a cutoff of 0.205 allows detection of 90% of the
cancers, and 38% of the negative biopsy findings can be
eliminated. If the patient has a normal-sized prostate on DRE, a
value of 0.234 is necessary to detect 90% of the cancers,
sparing 31.3% of the patients an unnecessary biopsy.
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Prostate-Specific Antigen (PSA),
Ultra sensitive |
| Ultra sensitive
prostate specific antigen (PSA) assays allow a lower
limit of detection (less than 0.01 ng/ml) than standard
PSA assays
This
test is intended for use as an aid in the management of
patients following surgical or medical treatment for
prostate cancer. The use of PSA as an aid in the
management of prostate cancer patients after treatment
has been well documented.1 The frequency of cancer
recurrence correlates with the degree of cancer
progression at the time of treatment.2 It has been
estimated that cancer relapse following radical
prostatectomy occurs in 3% to 11% of patients where the
tumor is confined to the prostate. Fifteen percent to
40% of patients with tumors extending beyond the
prostatic capsule will have cancer recurrence and to 30%
to 66% for patients with positive surgical margins or
invasion of seminal vesicles will experience relapse.
Biochemical recurrence, defined as increasing PSA levels
after treatment, can be observed much earlier than
clinical signs of tumor recurrence.3,4 Persistent
elevation of PSA following treatment or an increase in a
post-treatment PSA level has been found to be indicative
of recurrent or residual disease.5,6,7,8,9,10,11 The
lead time for the detection of cancer may be increased
by months, or even years, through the use of
ultrasensitive PSA.12,13 The ultrasensitive PSA test has
a functional sensitivity of 0.01 ng/mL, which is an
order of magnitude greater than that of other
conventional assays (0.1 ng/mL).
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Colon
Cancer Screen
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Colon (colorectal)
cancer, often called the "silent killer" ranks as the second leading cause of
cancer death
in the United States.
Colon cancer
affects both men and women about equally and kills more people annually than either breast cancer or prostate
cancer.
Too few people taking an
active role in monitoring their own health to prevent this disease
because of neglect, lack of awareness, lack of media attention,
embarrassment and the "yuck" factor.
No one has to
die from colon cancer.
With over a 90 percent cure rate caught early enough, colon cancer is
preventable and treatable.
Early
detection through screening is the key.
The
Best Test Is the One That Gets Used
- Only 37% of colorectal cancers are
detected at an early stage, when most treatable.1
- At least 60% of the 80 million
Americans over the age of 50 have never been screened.2
- 30,000 lives could be saved annually
if colorectal cancers were detected at an early stage.3
Colon cancer deaths could be nearly eliminated if most people
learn the
basics, talk to their family and physicians about it, and take
action to prevent it. Unfortunately, as recent government surveys and
studies show, less than 40% of people who should be screened have been
screened. Respondents age 50 and over to a recent survey said only 51% of
their doctors discussed colon cancer screening with them.
Prevention of colon cancer and other digestive disorders starts with
you. It requires that you take an active role in your own health. That
means know the basics: 1) the early warning signs and
symptoms of colon cancer, 2) whether you have a family history of
cancer requiring earlier screening measures than the average population,
3) the different screening methods available, and 4) the best
screening tests to use. It also requires that you engage in: 1) a
regular regimen of screening, and 2) an educated and active dialog with
your health care provider so they can provide the best available
preventative care.
Healthy eating habits and lifestyle
can be useful prevention measures, but scientific evidence clearly
weighs in favor of a regular regimen of screening as the best and most
reliable form of colon cancer prevention. The goal of screening is to
detect and remove pre-cancerous polyps - the source of nearly all colon
cancers. A simple screening regimen, regularly used, can literally mean
the difference between life or death.
Although colon cancer can strike with
no warning signs, one of the most frequent and commonly the only early
warning sign is blood in stool from bleeding polyps. Too often this
sign is either not noticed because the blood is not visible to the human
eye or not acted upon.
A healthy, normal individual does not bleed internally. If you do
bleed internally, resulting in either occult (hidden) or visible traces of
blood in stool, this can be a sign of colon cancer or other digestive
health problem that requires immediate medical attention.
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The information provided on this site is
for informational purposes only and is not intended as a substitute for
advice from your physician or other health care professional or any
information contained on or in any product label or packaging. You
should not use the information on this site for diagnosis or treatment
of any health problem or for prescription of any medication or other
treatment. You should consult with a healthcare professional before
starting any diet, exercise or supplementation program, before taking
any medication, or if you have or suspect you might have a health
problem. You should not stop taking any medication without first
consulting your physician. |
Affiliate - Cleveland
Clinic & University Hospital Network
Cleveland OH 44134
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