Re: Medical Research-Evidence


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Prostate cancer treatments are being evaluated, such
as
the
PIVOT
study. But some going on for 10 years have yielded no
results
yet,
strongly
suggesting that all current modes of treatment cure
those
who
would
not
die
of the disease anyway. Those who advocate PSA tests and
aggressive
treatments now claim that the best results will show up
AFTER
15
years!!!
But that is another 5 years out, and then it will be
raised
to
20.

There is recent 10 year data showing a survival benefit of
surgery
vs.
watchful waiting. It's long been known that survival
benefit
studies
would
need to go out at least that far except in metastatic
cases.



Here is a comment from another newsgroup:

Both Dale and George are correct.

Dale is correct in that radical prostectomy has been shown
to
lower
the
death rate due to prostate cancer (see the New England
Journal
of
Medicine article at:
http://content.nejm.org/cgi/content/abstract/347/11/781).

George is correct in that radical prostectomy has been
shown
to
have
no
significant difference over watchful waiting in overall
survival
(see
the New England Journal of Medicine article at:
http://content.nejm.org/cgi/content/abstract/347/11/781).

Now, what do you have to add with a link?

You're using outdated information. That study had a mean
followup
of
only
6.2 years, which was too short for a survival study with
prostate
cancer.
Allow me to refer to a followup the same study you posted
above,
done
with
the same patient population and the same authors, just longer
timepoints
for
data:

3 years later, a newer/better study was published in the same
Journal:

"Radical Prostatectomy versus Watchful Waiting in Early
Prostate
Cancer",
May 12, 2005 by Bill-Axelson and Holmberg et al. (same
authors,
longer
followup)
This paper is *the* landmark paper for this topic in the
field.

The study showed that "radical prostatectomy reduces
disease-specific
mortality, overall mortality, and the risks of metastasis and
local
progression".


and then the following, which is what Herman talks about
allowing
the
patient to make decisions:

You're welcome for the reference.

"THE ABSOLUTE REDUCTION IN THE RISK OF DEATH AFTER 10 YEARS IS
SMALL...."

The risk of death was not seen at 6 years, which was to be
expected.
3
years later it was noticed - before it should have been expected
to
be
seen - and was both clinically and statistically significant.
The
more
time
that elapses, the more signficant the differences will become.


This was expected for high-dose chemotherapy for recurrent
breast
cancer
too, but it did not work out that way. (The so-called bone
marrow
transplants).

Even if the results get no better than they are now, their is a
signficant
difference, clincally and statistically.

What Herman was trying to tell you is that this is not so.

Herman is not a a doctor and a physician is in a better situation to
determine what is CLINICALLY significant.


You remind me of the Catholic church when it came up with a marriage
questionnaire. It could not be looked at statistically because it was
a
holy document.

Clinically as used by your is a mystification technique. It is
meaningless. The only issue is whether a treatment works.

What Herman was trying to tell you is that in decision theory he
would
rather trust a treatment which cured 3 out of 3 than 2% more of a large
group of people. Why? Well, too many variables not controlled for.
What
if
they go back now and find that those who were 'cured' were only those
who
did NOT have the newly-discovered gene? Or did have? Or what? Very
small
differences in cancer survival rates over very long periods of time may
be
significant at the .05 level, but relatively meaningless at the
individual
level. When effectiveness is unexplained, then Herman brings up a
valid
point.

Yes, his comments on statistics are valid. On a separate note, the study
showed a small but clear survival advantage with surgery vs. watchful
waiting. We will see what further studies show.


Herman's comment that he would rather go with a study where 3 out of 3
are cured than with a large study showing very small differences. It is a
valid point. He is in favor a Bayesian methods. Even the New York Times
had an article comparing the approaches.

I'm not disagreeing, which you don't seem to understand. However, we don't
have such results. What we have is a larger study showing a smaller
response, but nonetheless, it showed that patients were cured from surgical
intervention for prostate cancer. Small numbers? Yes. But lives are lives
so meaningful numbers.

Very small
differences must be evaluated carefully even if statistically
significant.
The original authors state differences are small. Why dispute them?

I'm not disputing them. I support them. You just don't seem to
understand
that a relatively small difference can be a very important one...
especially if you're amonge the extra 20 lives saved in that study.

The problem is that when you rerun the study, with low levels of
significance you might just as well find the opposite, as the HRT
studies
showed or seemed to show.

you're living in hypotheticals now. Fact - the study showed a survival
advantage for surgery vs. watchful waiting. It's the best study we have
right on that topic.

Actually according to what Herman has posted over the years, it is not
hypothetical at all, but a possible artifact.

Yes, an unlikely possibiltiy, but nonetheless a possibility. This is why
multiple studies are being done and why the same study in question will
continue to evaluate their results over the years. The quality of the study
from this one study was excellent and I find the results believable. If
held true over time and confirmed by other studies, the issue will have no
doubt left. The doubt at this time is minimal.


.

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