[ RadSafe ] Fwd: LNT and Medical Radiation

[Chris Alston]

Andy

Generally speaking, there's no question that you're right about the
*appropriate* use of ionizing radiation in medical imaging and therapy.
This is why, for instance, the sub-specialty of interventional radiology
(minimally invasive surgery, guided by fluoroscopy) is growing by leaps and
bounds.  The serious questions about it are mainly about excessive,
unnecessary, or inappropriate usage (as, say, CT scans for *any* head
injury, or the use of it in cases where other imaging methods, such as
ultrasonography, are equivalent and may be cheaper (aside from any
"savings" on radiation dose), and there are increasing questions about the
effectiveness of stenting in interventional cardiology), overuse (e.g.,
repeat scans at different facilities for the same pts, which add no useful
info), and the use of larger amounts of radiation than necessary to produce
high-quality images, or, put another way, to tell the docs what they need
to know.  We also need to find ways to remove the profit motive from
imaging and tx.  It's just scandalous that, by example, urologists can set
up clinics to treat early stage prostate Ca with XBRT (external beam rad
tx), because they can make so much more money thereby.

Half of all Ca patients get radiotherapy, of one kind or another.  It can
greatly reduce mortality and/or extend life expectancy.  That is, increase
the probability of a curative course of treatment, offer treatment where
surgery is not possible, or too risky, or add years of good-quality life,
for pts with incurable disease.   There also is extensive use of imaging
(PET/CT/MV and kV) for tx planning, and for beam-guidance during treatments
(cf. the CyberKnife).  The risks of radiogenic primary tumors from
radiotherapies are well known (a possible exception is I-131 in thyroid Ca,
where the epidemiology has been challenging to study).  I seem to remember
an observation by Eric Hall, from years ago, that 1/100 pts who gets
radiotherapy develops another primary tumor, secondary to the treatment.
That is likely over all pts, so maybe some sub-populations have higher
incidences.

The basic priority in treatment planning, at the best centers, is give the
highest possible dose to the tumor, with appropriate margins, while
limiting the radiation dose to healthy tissue as much as possible, partly
to control deterministic, relatively early (weeks to several years) side
effects, but also to limit the risks of cancers secondary to the
treatment.  So, for a woman who has XBRT for breast Ca, the conscientious,
pt-focussed, radiation oncology team will take great care to limit the dose
to the contralateral breast (to control the risk of a radiogenic tumor in
that breast) and to the heart (to control the risk of radiogenic heart
disease).

People are studying this continually.  You might want to check out NYU's
website ( http://www.med.nyu.edu/radonc/ ) they are pretty much
state-of-the-art (sans protons), as far as I can tell.  I see that Silvia
Formenti, who was the chief RO doc there, until very recently, has gone to
Weill-Cornell, evidently as the founding chair of its department of
radiation oncology.  I mention this because she is a leader in the tx of
breast Ca, and in the personalized dx and tx of neoplastic disease.

Cheers
ca
---------- Forwarded message ----------
From: KARAM, PHILIP <PHILIP.KARAM at nypd.org>
Date: Sun, Nov 1, 2015 at 1:29 AM
Subject: Re: [ RadSafe ] LNT and the WHO guidance on red meat
To: "The International Radiation Protection (Health Physics) Mailing List" <
radsafe at health.phys.iit.edu>
I guess there's something else to consider, then, when we talk about
medical radiation - the benefit (and risk reduction) from the medical
exposure. Taking your example of an x-ray to avoid exploratory surgery, I
think it would be very reasonable to compare the risk from undergoing
surgery to the risk from receiving an x-ray or CT scan. Similarly, I'm
guessing we could also compare the risks of, say, chemotherapy-only instead
of chemo + radiation therapy versus the risk to one's health from the
scattered radiation (or, in the case of I-131 therapy, risk to non-thyroid
tissues from the I-131 uptake).  In the case of diagnostic and
interventional radiology my guess is that, when properly used, the risk of
NOT having the diagnostic information exceeds the risk from the procedure -
in the case of therapeutic radiation I suspect you'd have to look at the
time post-irradiation to have a good understanding of the overall
radiological risk.
But we should also remember that many medical conditions can kill you in
minutes, hours, or days while radiation-induced cancer shows up years to
decades later. Even if a diagnostic procedure eventually gives me cancer,
I'd still consider it a net reduction in risk if it made it possible for me
to survive those extra years or decades.