JOHN wrote:
> http://www.whale.to/a/psa_test.html
>
>
This is a classic example of using partial information to mislead. I am
also amused by a chiropractor acusing the medical profession of
quackery. It is usually the other way around.
Let's analyze the quoted statement.
"there is no proof that the use of the PSA blood test to screen
symptom-free men will spare anyone a prostate cancer death, yet it is
associated with a considerable amount of unnecessary treatment with
aftereffects that can be both severe and permanent."
These statements are true in the following restricted sense. "Proof"
here means a so-called prospective, randomized test. This is often
considered the gold standard in establishing the value of a medical
procedure. But it is not the only line of evidence that is available.
For example, in the US where screening is relatively common, not only
has the mortality rate for prostate cancer declined but the actual total
number of deaths has declined. In Austria, screening was introduced in
one part of the country and there deaths from prostate cancer declined
relative to those in the rest of the country. That kind of evidence may
be questioned because other factors could be at play and, theoiretically
at least, a prostpective randomized study can avoid the effect of such
'confounders'. But, there are also problems with running a prospective
randomized study for a disease like prostate cancer which develops
slowly and has a long time horizon. There is ongoing in the US just
such a study, the PIVOT study. Its results are not yet in, so we don't
know what it will find. It is designed to follow men for a certain
period of time, 10-12 years I believe. It is not at all clear that this
is long enough. Similar studies in Sweden comparing treatment to
watchful waiting, a related question, found little difference between
the two for up to ten years but later followups showed differences
developing afterwards.
Note also that the absence of proof is not the same as the proof of
absence. If you are a man over 50, you should be aware that although
there is some evidence that PSA testing is useful, there is no certainty
about it at present. The implication of the posted material is that it
is an established fact that you are highly unlikely to benefit from PSA
testing. Of course, that is not true. There is little evidence to
support such an asserion.
"All of the treatments for early prostate cancer carry the risk of
impotence and incontinence. In short, cancer researchers do not know
whether PSA screening saves more lives than it ruins."
Again, this implies that that PSA screening ruins more lives than it
saves, and again the statement depends on an interpretation of the word
"know". Certainly highly reputable medical scientists believe that
there is evidence that screening is overall beneficial, even if they
can't presently prove it beyond all statistical doubt. It should also
be noted that prostate cancer also carries the risk of impotence and
incontinence. Indeed, it is highly likely to produce those effects.
If your prostate cancer is detected after it has metastasized, the only
available effective treatment today is hormone suppression therapy,
which will have profound effects on your body. You may be technically
potent, but most likely you will have no interest in sex. Urinary
problems will develop as the cancer presses on the urethra and treatment
for that may result in incontinence. Eventually such therapy fails and
you will face serious pain and ultimately death. Moreover, although
incontinence can follow early treatment for prostate cancer, serious
incontinence following such treatment is relatively rare if the
practitioner is competent. Impotence is more common, but if you are
relatively young and your doctor is skilled, you have an excellent
chance of avoiding it. Moreover, impotence can be treated, and it
doesn't mean the end of an active sex life. Saying that men's lives are
generally ruined by modern treatment methods is a gross exaggeration and
highly misleading. Of course, some men do have serious problems
following treatment, but the same could be said of any medical procedure.
Note that the emphasis on PSA testing conflates several issues.
Testing by itself is pretty innocuous. It is what you do after a test
proves positive that matters. First, there will be a biopsy. This is
an invasive procedure, but it is relatively safe and seldom has adverse
consequences. If the biopsy shows the existence of cancer, the patient
then has to decide what to do about it. The critics, as in this
posting, suggest that aggressive treatment, with its attendant risks, is
then predetermined. But that need not be the case if the doctor is
competent. For example, for a moderate case, few competent urologists
will recommend aggressive treatment in a man with a life expectancy
under 10 years. Since the great bulk of prostate cancer occurs in men
over 65, many of these men need not be treated and only need to be
followed.
It should also be noted in connection with this that a recent
prospective, randomized study---gold standard---comparing radical
prostatectomy to watchful waiting found that radical prostatectomy
resulted in less prostate cancer mortality, less overall mortality, and
fewer signs of progression to advanced metastatic disease. It was all
the more remarkable that the advantage of radical prostatectomy showed
up as early as and average of six years following treatment.
Finally,
"If you look at the prostate cancer outcomes from a huge study conducted
by the National Cancer Institute, close to 40% of men who undergo a
radical prostatectomy will have a PSA relapse within two years."
This has got to qualify as lying by telling a limited truth. I don't
doubt that there was such a study. But the conclusion is totally at
variance with recent studies on the effectiveness of treatment for
prostate cancer. Note also the subtle shift in emphasis. First the
impication is that the vast majority of men treated for prostate cancer
are subject needless to side effects when their cancers will never
bother them. Then we are told that if treated, within two years, they
are likely to show evidence of recurrence of the cancer through a rise
in PSA. Such PSA recurrence usually is an indicator of the development
of clinical symptoms somewhere further down the line, so such patients
are at significant risk of advanced metastatic cancer if they live long
enough.
The unstated implication of this posting is that under all
circumstances, if you have prostate cancer either it will be innocuous
and never bother you or it will kill you whether you are treated or not.
There is certainly no evidence supporting such an implication and lots
of evidence contradicting it. As I noted above, thre is even a
prospective, randomized study which contradicts that assertion.
PSA test 
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