‘No evidence that CT scans, X-rays cause cancer’


RESEARCHERS conclude there is no proof that low-level radiation from medical imaging – such as X-ray and computed tomography scans – causes cancer. They say it is time to throw out an unproven, decades-old theoretical model that has led many people – doctors and regulators included – to believe otherwise.
The researchers say the model that is used to estimate the potential cancer risk of low-level radiation from medical imaging machines – such as this CT scanner – is wrong and should be abandoned.
Writing in the American Journal of Clinical Oncology, the researchers describe how the linear no-threshold model (LNT) – first proposed over 70 years ago – is used to estimate cancer risks from low-dose 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 theoretical, and, as yet, “have never been 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 low-dose 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 low-dose radiation exposure by simply continuing in a straight line from the well-established, undisputed effects of high-dose radiation.
But such a model ignores the fact that the human body is able to repair damage caused by low-dose 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 low-dose 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. 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. X-rays or computed tomography (CT) scans – at doses well below those of the background radiation.

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