'No Evidence That CT Scans, X-Rays Cause Cancer' - Medical News Today
'No Evidence That CT Scans, X-Rays Cause Cancer' - Medical News Today
'No Evidence That CT Scans, X-Rays Cause Cancer' - Medical News Today
Cancer / Oncology (/categories/canceroncology) Radiology / Nuclear Medicine (/categories/radiology)
(/)
'No evidence that CT scans, Xrays cause cancer'
Written by Catharine Paddock PhD (/authors/catharinepaddockphd)
Published: Thursday 4 February 2016
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R esearchers conclude there is no proof that lowlevel radiation from medical
imaging such as Xray and computed tomography scans causes cancer. They
say it is time to throw out an unproven, decadesold theoretical model that has led
many people doctors and regulators included to believe otherwise.
Writing in the American Journal of Clinical
Oncology, the researchers describe how the
linear nothreshold model (LNT) first proposed
over 70 years ago is used to estimate cancer
(/info/canceroncology/) risks from lowdose
radiation, such as medical imaging.
But say James Welsh, a radiation oncology
professor in the Stritch School of Medicine at
Loyola University, Chicago, IL, and colleagues
risk estimates based on the LNT model are only The researchers say the model that is used to
estimate the potential cancer risk of lowlevel
radiation from medical imaging machines such as
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2/25/2017 'No evidence that CT scans, Xrays cause cancer' Medical News Today
theoretical, and, as yet, "have never been this CT scanner is wrong and should be
abandoned.
conclusively demonstrated by empirical
evidence."
They say persistent use of the LNT model by regulators and advisory bodies leads to unfounded
fears and money being wasted on unnecessary safety measures.
As a result, many doctors are averse to recommending and using the most appropriate imaging
procedures for their patients, and many patients are unnecessarily scared to undergo them.
Model ignores that human body repairs lowdose radiation
damage
The LNT model maintains there is no safe dose of radiation no matter how low the dose. It says you
can work out the cancer risk of very lowdose radiation exposure by simply continuing in a straight line
from the wellestablished, undisputed effects of highdose radiation.
But such a model ignores the fact that the human body is able to repair damage caused by lowdose
radiation something that has evolved over millennia in humans and other organisms that are
continually exposed to naturally occurring radiation in the environment. The authors note:
"We are literally bathed every second of every day in lowdose radiation exposure due
to natural background radiation, exposures that vary annually from a few mGy to 260
mGy, depending upon where one lives on the planet."
They go on to explain how no associated health effects as a result of being exposed to this background
radiation have been documented anywhere in the world.
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2/25/2017 'No evidence that CT scans, Xrays cause cancer' Medical News Today
In fact, people in countries like the US are living longer than ever likely because of improvements in
medical care that involve exposure to radiation from diagnostic equipment e.g. Xrays or computed
tomography (CT) scans at doses well below those of the background radiation.
In their paper, the authors describe how they revisited the studies from over 70 years ago that led to
widespread use of the LNT model.
Lowdose risks are not an extrapolation of highdose risks
The studies published in the 1940s exposed fruit flies to various doses of radiation, but not very low
doses. Nevertheless, they concluded that to estimate the risk of those effects occurring at low doses,
you simply continued in a straight line down the plot result from the higherdose experiments.
When scientists carried out the same experiments on fruit flies in 2009 using low doses of radiation
they did not find the results to be as predicted by the original studies.
Also, note the authors, studies of human populations exposed to radiation including nuclear bomb
survivors have never conclusively shown that lowdose radiation increases cancer risk.
They urge people to vigorously challenge any claim that lowdose radiation from medical
imaging is known to cause cancer.
To back such claims only "serves to alarm and perhaps harm, rather than educate," they note, as they
conclude that the LNT model "should finally and decisively be abandoned."
Meanwhile, Medical News Today recently learned how scientists have discovered a surprising new clue
to how cancer tumors form (/articles/305639.php). It appears that a small minority of cancer cells
extend "cellular cables" to draw in nearby cells including a lot of healthy cells into the tumor
(/articles/249141.php).
Written by Catharine Paddock PhD (/authors/catharinepaddockphd)
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