Re: Alpha radiation and LNT

[David Scherer <scherer@uiuc.edu>]

In my simple suggestion I didn't intend to propose a numerical model for the
cellular processes involved.  Instead, my primary question is whether the
response of tissue to alpha radiation says anything at all about the
response of low LET radiation.  Do we simply assume the two are similar, or
is there a firm basis for the assertion?

As an aside, at high doses cell killing is not linear with dose.  To first
approximation it is exponential, but with a shoulder at low doses.  The
exponential constant, D-sub-0, and the breadth of the shoulder, D-sub-q, are
different for high and low LET radiations, oxygen tensions, etc.  (Recall
those clasical cell survival curves.  The shoulder is an important element
in clinical radiation therapy fractionation.)

Let me be even more provocative and advance the arguement further. At low
doses, there is a broader shoulder in low LET radiation and almost no
shoulder with high LET radiation.  This means there is more cell killing
going on with alphas than beta/gammas.  So perhaps you would expect more
dead cells and fewer cancers with alphas at these low doses?  Who knows!

In any event, the debate about LNT is over its use to predict mortality in
the overall population, not just the molecular initiation mechanism.  This
includes promotion, immune response, and even respone to therapy as they
affect mortality.  (Sound pretty complicated for a straight line model.  But
again, I'm not a biology researcher.)

Regards,
Dave Scherer
scherer@uiuc.edu