Re: Medical Research-Evidence


"George Conklin" <georgeconklin1@xxxxxxxxxxxxx> wrote in message
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"George Conklin" <georgeconklin1@xxxxxxxxxxxxx> wrote in
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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You're using outdated information.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.

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.

I'm not one of those guys who advocates prostatectomy for every
patient
with
prostate cancer. I think there are a large number of patients for
whom
watchful waiting is appropriate. However, we can now say,
conclusively,
that in the face of diagnosed prostate cancer, surgery will save
lives.

Well, if you believe the data, a few. What about surgical
mortality?
Did they happen to include that?

Of course. If I recall, there we no reported deaths. I'm at an
institution
that does about 5-10 per week and I can't recall the last time we had
a
mortality from this surgery. But yes, mortality was included and
should
always be inlcuded in such outcomes studies.

OK.

As for believing the data, I'd hope you would believe, since it was
merely
an extension of a study that you believed enough to post a link to.


I read the article, and noted that the differences are small. I
wonder
why the American studies are holding back their results.

See below, they just finished enrollment a few years ago, which is about
5
years after the Euro study finished enrollment. That's why.


I understood that 8 years should be enough for preliminary results. The
Euro study rushed into print with that time frame. The USA PD said
nothing
had emerged so far, at least on the radio. I am assuming silence since
then
makes the same conclusion hold.

we know what happens when one assumes. I prefer to wait for the study
results before concluding what the study showed.

Just a few
differences in classification of deaths in the study you cite would
change
the results.

Yes. It may have lessened the results. Or it may have strengthened
them.

When multiple causes of death are present, a committee
decision that death was due to disease 1 or 2 is highly subjective.
Those
comments were widely discussed at the time the study was released.

All cancer survival studies have this problem - so while I agree that it
is
an issue, it's not one we can avoid. I could, of course, use the same
argument to say there may be differences in studies that didn't show a
difference for this very reason... but since there isn't a good way
around
it, I leave it alone. So should you.

So much depends on the age of the patient and how many other
confounding
diseases are present. That is one reason why Herman thinks that decision
theory is important and raw levels of significance are NOT. Yet you in
different posts said you cannot compare nations. So how can you object to
much more immediate concerns?

Of course there are cofounders. That is why the study was a randomized
controlled trial - it's the best study we have to try to control for
confounders. Perfect? Nothing is, but again, it's the absolute best study
that can be designed.

The American studies

Are not done yet.

are 10 years old and have no released their data
yet. Had they found even 1% differences, they would have gone to
the
press
and hollared loudly. The PIVOT studies seem silent too. Why? No
results.
There were a lot of other questions raised by the Scandinavian data
too
last
year.

FACT:
The Euro study completed enrollment in 1999. PIVOT just completed
enrollment 2 or 3 years ago. The data are far too immature and won't
be
ready for a few more years.


On NPR there was a study from a man who called it the "Minneapolis
Study,"
as I recall, and it had been going 8 years with no results. The study
director was interviewed. I did not have a tape machine going.

You can speculate all you want. The FACT is that the study close
enrollment
a half decade later than the recently published Euro study, so their not
having results yet is entirely expected.

8 years was enough time for the Euro study to rush to print.

and clearly that was premature, as their later data showed a change.
Perhaps the American group learned from their mistake. I don' t know or
care - speculation is worthless. We'll see what the results are when they
have them. You and the rest of the world will see what they are when they
get published.

Prostate cancer is very different from kidney cancer. Survival will be
more
difficult to show, it will take much longer studies, etc. Kidney cancer
or
bladder cancer is quite the opposite. If not treated pronto, either can
progress rapidly to death. Surgery can result in cures in large numbers
of
patients, espeically lower stage disease. The numbers depend on the type
of
cancer, the stage, the treatments, etc. But there is not the same
controversy as there is with prostate cancer - with renal and bladder
cancers rapid surgical intervention clearly can be life saving for many.

Well, at least for some.

Many. Look up the numbers for yourself if you're interested.

Unfortunately until the biology of prostate
cancer is figured out, we are left with treatments which have yielded
'small' results either way. I guess you have to stick to being an
optimist
but very very slow 'progress' with adult cancers shows that in general
medicine is not going to cure people with surgery on the prostate, or at
least few. We all know people with low-grade prostate cancers who died
about 7 years after their radical operations, right 'on schedule' if you
will.

The data have shown surgery saves lives at earlier timepoint than expected.
Saving some lives is better than saving none.


.

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