[ RadSafe ] Re: AW: Log-log plot for excess breast cancer incidence rate
John Jacobus
crispy_bird at yahoo.com
Fri Jul 22 16:54:39 CDT 2005
George,
Again, maybe I misunderstood. However, I would like
to get your comment on the breast risk model given in
the BEIR VII report that is attached.
I am somewhat out of my league with the analysis you
are doing. However, I would like to get your
prespective on the conclusions of the BEIR VII report
since this is more relevant to me.
--- George Stanford <gstanford at aya.yale.edu> wrote:
> John:
> Thanks for the info. However, I have made
> no
> comments regarding leukemia. My remarks pertained
> specifically to the data for hemangiomas that Rainer
> Facius extracted from the paper by Preston et al. I
> observed, specifically, that the LNT model fits
> those
> data within the experimental error limits. That
> said,
> a threshold model with some hormesis fits the
> data considerably better.
> Cheers,
> George
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> At 04:17 PM 7/21/2005, John Jacobus wrote:
> George,
> The BEIR VII says that leukemia follows the
> linear-quadratic model. It is the solid tumors that
> follow a linear fit.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> --- George Stanford <gstanford at aya.yale.edu> wrote:
> ---------------------------------
> Rainer:
>
> Thanks for the additional information, and
> the
> two new graphs.
>
> I'm afraid I have to take issue with you on
> one
> point.
>
> When fitting a curve to data, one has to
> use
> the observed values consistently. That is what I
> did
> with my fits. The observed residual background on
> the
> plot that I used is not zero. It is approximately
> 25.
> It's certainly legitimate to subtract a constant
> from
> the background, which is what you did. Subtracting
> the
> entire observed background leads to negative data
> points -- no problem on a linear graph, but awkward
> in
> a logarithmic representation(as you have pointed
> out).
>
> If you were to repeat my process with the
> full
> background, the result would be the same. The LNT
> model** fits the hemangioma data within the reported
> experimental error limits.
>
> In your earlier graph, you selected the
> extreme
> (lowest) data point from the low-dose region to use
> as
> the observed background. That led to the weird
> result
> that you depicted an excess of low-dose cancers --
> exactly the opposite of what we are claiming. If I
> understand your new loglog plot
> (PrestonHemExcess(1-1000)loglog.gif), you
> have corrected that problem, and the result is the
> same
> as mine -- the LNT fit is within the error limits.
> That's something we have to live with-- accept it,
> and
> move on.
>
> The interpretation of the other graph
> (PrestonHemLowFits.gif) escapes me, since it has
> lines
> with negative slopes labeled "LNT" --clearly not the
> conventional LNT -- but, as instructed, I will
> refrain from asking for an explanation. Maybe it
> will
> dawn on me sometime.
>
> Best,
>
> George
>
> ** I can't think of a better term --"model" does
> not imply that it's a good model. The quadratic
> model
> is better.
>
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> At 08:12 AM 7/20/2005, Rainer.Facius at dlr.de wrote:
>
> George:
>
>
>
> Thank you for providing a near perfect example for
> what I intended toinstigate with my original note to
> E.M. Goldin.
>
>
>
> In contrast to what a few others have insinuated, I
> did and do notwant anybody to believe in anything,
> least of all in my statements butalso neither in fit
> parameters nor even in peer review and committees.
> Iintended to make them look at the data and generate
> their ownconclusions, as you do. The only arbiter of
> truth - within the limitedrealm of science is
> data.
> (BTW, in my view the prime function of peerreview is
> to make sure that the provenance of the data and
> theirdependability are spelled out as extensively as
> necessary and asprecisely as possible, something
> which
> appears to beretreating.)
>
>
>
> Yet, I am afraid you have fallen in one of the traps
> which I tried tocaution against previously, in
> particular with respect to log-logrepresentations.
>
>
>
> In the graph to which you added your fit lines and
> which you did attach,one reasonable/feasible
> estimate
> of the background HAD ALREADY beensubtracted (note
> the
> ordinate label), namely the incidence rate in
> theminimum at [500,1000] mSv so that your term “bkg”
> would have to be zeroinstead of 25. In this graph
> the
> straight line D^1 is already a (visual)LNT estimate
> of
> the EXCESS (above the minimum). If you wish to avoid
> theextreme values, either minimum or maximum,
> another
> reasonable/feasibleestimate would be the average
> between 0 and 1000 mSv, which
> is[44.9,51.7,59.3]-95%CI. I attach yet another graph
> with this averagealready subtracted as background
> (watch the ordinate label). Thereforeagain, the
> straight lines are already visual fits for the
> respectiveexcess.
>
>
>
> By now you have ‘talked’ me into doing what I still
> consider a pointlesseffort given the reduced
> published
> data to perform some formal fits tothe data in the
> low exposure range. For that purpose I had to
> convert
> theasymmetric 95% confidence interval into symmetric
> standard errors bydividing the confidence range by
> 4.
> For the x-values I took the middle ofthe respective
> interval for which the averages were specified. I
> fitted alinear quadratic and a linear model to the
> data up to 2500 mSv and asecond linear model to the
> range relevant for radiation protection, i.e.,below
> 1000 mSv. I include a copy of the fit statistics
> provided by theORIGIN PRO 7.5 program. You may use
> them as you like and can make senseof them but
> please
> don't ask for explanations.
>
>
>
> I attach the corresponding graph too. It’s up to you
> to judge to whatextent this might be considered a
> case
> for LNT with a slope>0.
>
>
>
> Whatever the bottom line might be, thank you for
> your
> motivatingcontributions to approach it.
>
>
>
> Kind regards, Rainer
>
>
>
> Here come the STATISTICS belonging to the fits:
>
>
>
> [20.07.2005 12:17 "/DATA/Graph1" (2453571)]
>
> Polynomial Regression for HMSwP_G:
>
>
=== message truncated ===
+++++++++++++++++++
"Every now and then a man's mind is stretched by a new idea and never shrinks back to its original proportion." -- Oliver Wendell Holmes, Jr.
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird at yahoo.com
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