CT Scans Save Lives

By Scientists for Accurate Radiation Information (SARI)

We are writing to express our concerns with a January 30, 2014 article by Rita F. Redberg and Rebecca Smith-Bindman. The article is alarmingly titled, “We Are Giving Ourselves Cancer”, and is accompanied by a frightening cartoon that appears to be a doctor holding an X-ray film, and wearing a gas mask and helmet. The picture and title are the first clues that sensational claims follow, and the article does not disappoint in that regard, though it falls far short in offering prudent medical advice to frightened patients and parents.

The authors only mention in passing that medical imaging can save lives, and quickly move on to assert that there is little evidence of better health outcomes from current scanning practices. They do not mention, for example that the National Lung Screening Trial recently found that former smokers who received CT screening were 20% less likely to die from lung cancer and 7% less likely to die from any cause, compared to those who were screened with lower dose chest radiography. They do not mention the studies demonstrating the clear clinical benefits of mammography, bone mineral densitometry, and CT colonography. They do not mention the hundreds of studies that suggest that the body’s natural defense systems are quite capable of dealing with very low doses of radiation – like those that have existed on our planet since its beginning and those associated with modern medical imaging. They do not mention the hundreds of other studies that suggest that low radiation doses may in fact stimulate patients’ natural
defenses against cancer (many of which can be found at http://radiationeffects.org).

Instead, the authors claim that we are “irradiating ourselves to death” with medical diagnostic imaging, especially CT scans. They selectively cite two recent studies of children who received CT scans, both of which claim to observe increased cancer rates, which the authors claim is due to radiation from the scans. Unfortunately, these studies suffer from a number of methodological problems, including:

  1. The studies lacked proper controls. They should have included children who did not receive CT exams, but who had the same medical conditions as the children who did receive CT scans. This could lead to the erroneous conclusion that the CT scans caused cancer, when in fact the cancer was caused by the underlying medical condition that required the scan. For example, the most common reason for CT scans in children is head trauma – which itself has been linked to later cancer.
  2. The studies used questionable models to estimate risks. Risk estimates were based on the linear, no-threshold model of radiation risk – a controversial model used for conservatively setting radiation protection standards, but which is inappropriate for estimating excess cancers from CT scanning.
  3. The studies used questionable methods to estimate radiation dose received by patients. Radiation doses were not directly measured. Rather, age-based estimates were used that assumed, for example, that a newborn infant is the same size as a 4-year old child. As any parent knows, this is simply not true, and this could lead to large errors in dose estimates.

The authors’ unsubstantiated predictions of excess cancers caused by CT scans are far outside the scientific mainstream. The American Association of Physicists in Medicine (AAPM) – which is the professional society for physicists with expertise in medical imaging – has stated that the risks of medical imaging procedures “are too low to be detectable and may be nonexistent”. The AAPM also stated,

“Predictions of hypothetical cancer incidence and deaths in patient populations exposed to such low doses are highly speculative and should be discouraged. These predictions are harmful because they lead to sensationalistic articles in the public media that cause some patients and parents to refuse medical imaging procedures, placing them at substantial risk by not receiving the clinical benefits of the prescribed procedures.”

Similar advice against estimating radiation risks the way the authors did has been offered by the Health Physics Society, the International Commission on Radiological Protection, the International Organization for Medical Physics, the Society for Pediatric Radiology, and the United Nations Scientific Committee on the Effects of Atomic Radiation. The authors’ claims are simply irresponsible, and will harm children and adults by scaring them away from necessary exams.

So what are parents and patients to do? First and foremost, you should discuss any concerns you have with your family’s doctor. These are the professionals who have spent years learning medicine, and who you trust with your health and the health of your children. They have the most knowledge about your family’s health history. Doing some research on your own is also a good idea, but don’t believe every exaggerated claim you read in the newspapers or on the internet. Make sure to use reliable sources such as the Alliance for Radiation Safety in Pediatric Imaging’s website (http://pedrad.org/associations/5364/ig/WhatcanIdoasa/Parent.aspx) and the
Health Physics Society’s website (http://radiationanswers.org).

Signed:

Brant Ulsh, PhD, CHP, Principal Health Physicist, M.H. Chew & Associates, USA
Cynthia McCollough, PhD, Professor of Medical Physics and Biomedical Engineering Director, CT Clinical Innovation Center, Mayo Clinic, USA
Wade Allison, DPhil, Professor of Physics Emeritus, Oxford University, UK
James Conca, PhD, Director of the Center for Laboratory Sciences, USA
Jerry Cuttler, DSc, President, Cuttler & Associates, Canada
Ludwik Dobrzynski, PhD, National Center for Nuclear Research, Poland
Mohan Doss, PhD, MCCPM, Medical Physicist, Associate Professor, Diagnostic Imaging, Fox Chase Cancer Center, USA
Ludwig Feinendegen, PhD, Professor Emeritus, Nuclear Medicine, Heinrich-Heine-University, Germany, and Guest Scientist, Brookhaven National Laboratory, USA
SMJ Mortazavi, PhD, Professor of Medical Physics, Head of Ionizing and Non-ionizing Radiation Protection Research Center, Head of Shiraz University of Medical Sciences, Iran
Douglas M. Osborn, PhD, USA
Bobby R. Scott, PhD, Senior Scientist, Lovelace Respiratory Research Institute, USA
Alexander Vaiserman, PhD, Institute of Gerontology, Ukraine
James S. Welsh MS, MD, FACRO, Neutron Therapy Facility at Fermilab, USA

Note: All signers of this letter are members of SARI (Scientists for Accurate Radiation Information, http://radiationeffects.org/). The above letter represents the professional opinions of the signers, and does not necessarily represent the views of their affiliated institutions


Note from Atomic Insights: SARI originally submitted their February 1, 2014 letter to the New York Times as an op-ed in response to We Are Giving Ourselves Cancer.

SARI received an automated reply from the New York Times stating that the paper has a policy of not publishing op-ed’s that respond to other op-eds. SARI members feel so strongly about the importance of their message that they have asked Atomic Insights to help them reach a larger audience.

If you have access to a larger megaphone, please contact Rod Adams using the contact form at the bottom of the page.

About Guest Author

16 Responses to “CT Scans Save Lives”

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  1. Martin Nicholson says:

    Unfortunately many inexperienced individuals are heavily influenced by ex-medical professional Helen Caldicott who is a world famous anti-nuclear activist – and a very successful one too!

    Helen firmly believes and often states that “no dose of radiation is safe, however small”.
    http://www.helencaldicott.com/2011/04/how-nuclear-apologists-mislead-the-world-over-radiation/.

    If you accept this, then yes CT scans and x-rays are inherently unsafe. If there were accepted epidemiological studies that showed that CT scans did more harm than good then we would have been forced to abandon them decades ago.

    I find it bitterly disappointing that someone with Helen’s education could not see the falsehood in her propaganda. But I suspect the hole she has dug for herself is too deep to climb out of now.

    • SteveFost says:

      Yes, Helen fell into a trap. She started to believe her own propaganda and became even more self-sure, shrill and dogmatic. After decades constructing this facade, it is impossible to walk it back without a total loss of face and credibility, so the only option is to double down on her nonsense.

      I think there is a valuable less here for all of us. Stay humble and always make your ego and opinion subordinate to the data. Temptation is great to believe the narrative of one’s Greatness ordained by Providence, except that it is usually self-delusion propelled by arrogance. Humility and a hard-nosed dedication to the facts are vital if one is to be taken seriously and make a difference over the long haul.

      If the facts point in a new direction, you must be able to admit it and change course. Al Gore and his position on nuclear power is another example of this phenomena…

      • Joris van Dorp says:

        Fully agree. This counts for pro-nuke activists too. Speaking for myself, I am regularly called a ‘true believer’ by my opponents because I push the pro-nuke case (too?) hard. While I am careful to always remain within the limits of what I sincerely believe to be supported by scientific fact, I have found myself uncomfortably close to the edge a few times. This happened due to a combination of not having enough knowledge (there is always more to learn, especially for someone like me who came in late to nuclear science and technolog) and due to being the often outraged witness of the complete lack of dedication to facts displayed by most if not all anti-nukes, which makes it tempting to get sucked onto the deceptively easy highway of fact-free, gut-feeling advocacy.

  2. GaryN says:

    It will be interesting to hear what my doctor has to say, next time I see him, when I ask if I can get a dose of whole body gamma radiation as a ‘tonic’, keep the old imune system in top form. Wonder if he might know the optimal exposure values?

  3. Joris van Dorp says:

    In Wade Allison’s highly readable book “Radiation and Reason” there is a relevant part on the health impacts of radiotherapy with beam radiation. It is shown that cells’ reaction to such radiation exhibits a strong threshold response, whereby cells close to the tumor which receive up to 70% of the radiation dose survive intact, which the cells in the tumor receiving 100% of the radiation are all killed. That part of the book really illustrated for me how large the difference between dangerous and safe radiation doses really appear to be, at least concerning deterministic effects. Of course, it is the more complex (and thus easier to misrepresent) stochastic effects which anti-nukes mostly latch onto to bolster their FUD production…

  4. EL says:

    Modern equipment is routinely able to keep doses down to the 1 mSv range in cardiac and pediatric scans, and below 10 mSv on average.

    http://iopscience.iop.org/0031-9155/59/3/R129/

    It seems the medical community (and health care providers) have responded correctly to some of these issues concerning dose and elevated risk, and attempted to minimize unnecessary scans, perhaps costs as well, and improve health outcomes at the same time. As suggested in a widely cited review article here:

    There is a considerable literature questioning the use of CT, or the use of multiple CT scans, in a variety of contexts, including management of blunt trauma, seizures, and chronic headaches, and particularly questioning its use as a primary diagnostic tool for acute appendicitis in children. But beyond these clinical issues, a problem arises when CT scans are requested in the practice of defensive medicine, or when a CT scan, justified in itself, is repeated as the patient passes through the medical system, often simply because of a lack of communication. Tellingly, a straw poll of pediatric radiologists suggested that perhaps one third of CT studies could be replaced by alternative approaches or not performed at all.

    For those who are need of such scans, I see no health basis to suggest they should not be given one. But to give such scans on a general basis, simply to pay off the equipment, protect the doctor, or rack up costs … there appears to be little benefit to improving health outcomes, and pretty consistent evidence from other contexts (as suggested from above) that health risks would be elevated in such instances (particularly in cases where older equipment is being used, and doses range in the 30 – 90 mSv range for just two or three scans).

    We seem to be trending in the right direction on this one (towards lower doses) and not towards higher doses (and uncertain scientific evidence to suggest and give cover for unnecessary scans, higher costs, and perhaps even worse health outcomes than equally effective alternatives).

  5. Laurence Aurbach says:

    There is also the World Health Organization’s World Cancer Report 2014 in the news today. It says that radiation from medical scans is a major source of cancer.

    http://www.bbc.co.uk/news/health-26014693

    I have not read the report but I would guess its conclusions are based on estimates generated by Linear No-Threshold models.

    • Martin Nicholson says:

      Radiation (both from the sun and medical scans) is 5th on a list of 8 major sources of preventable cancer. The top 4 are Smoking, Infections, Alcohol and Obesity and inactivity.

      A news report like this might scare some away from medical scans. A challenge for the medical profession no doubt.

  6. EL says:

    They selectively cite two recent studies of children who received CT scans, both of which claim to observe increased cancer rates, which the authors claim is due to radiation from the scans.

    I wouldn’t mind getting a reference for the two studies they are citing here.

    The first one appears to be this:

    http://dx.doi.org/10.1016/S0140-6736(12)60815-0

    Authors suggest the case control study is forthcoming (here).

    The second appears to be this one:

    http://dx.doi.org/10.1136/bmj.f2360

    Which does include comparison with a control population (those who did not receive CT scans). In addition, age based groupings for dose estimates were as follows: “newborn; 1, 5, 10, 15 years; adult” (p. 2). They also utilized a scaling factor in some instances. Might they be talking about a different study?

  7. GaryN says:

    “They selectively cite two recent studies of children who received CT scans, both of which claim to observe increased cancer rates, which the authors claim is due to radiation from the scans.”

    Maybe x-rays aren’t the choise for beneficial radiation then? Numerous studies on those exposed to gamma radiation (from Cobalt 60) show less cancer and less chronic illness, and the numbers are well above any chance of statistical errors. The numbers for the excess cnacers from x-rays seem to be so small as to possibly be statistical error though. If I were seriously looking at getting irradiated for health reasons, I think I’d try and reproduce the type and levels or radiation experienced by those who live in regions with the longest-lived residents.

    • jmdesp says:

      You don’t give a head CT scan to a kid without a serious reason. This means that given that the excess is really small in absolute, some correlation between medical conditions that require a CT scan and cancer is a likely explanation (more than just statistical error).
      In the Australian study, they tried to avoid that, but it’s very hard. The study would be much enhanced by including what was the initial condition requiring the CT scan. They say they eliminated cancers occurring shortly after the examination, but I fail to see why radiations would be the only factor that has a long latency period (given what we know today about DNA, radiation cancer are most likely caused by defective DSB repair, but most other carcinogenic factors are also linked to defective DSB repair). They also say they found a link with the number of CT scan, but again more serious conditions also probably mean repeated CT scan.

      It would be more convincing if they could find a reduction after the hospital switched to a more modern machine with lower exposure. Especially if it still can be shown for two comparable hospital that didn’t receive the newer equipment at the same time.
      This kind of correlation and control has already been used to show a negative link between high speed Internet access and the number of rapes (more Internet results in less rapes).

  8. Joris van Dorp says:

    Stress is a cause of cancer and disease (and depression and substance abuse and an unhealthy lifestyle) all by itself.

    Tell patients who get CT scans that they risk getting cancer often enough, and I’d think it’s quite possible that their stress levels increase by just the right amount for anti-nukes to be able to document the resulting increase in cancer and other disease that they like to see.

    It would be interesting to see a study where a control group of patient is told they’ve recieved a CT scan which increases their risk of cancer, while in fact they received no such scan. I wonder if that control group would also show (barely statistically significant) increases in cancer or other diseases. Going further: have another group get actual CT-scans but tell them that their chances of getting cancer may now well be reduced due to hormesis effects, and see how that group does afterwards compared to the group who is told they run an increased risk of contracting cancer due to the scans they recieved. I wonder.

    At the very low radiation doses and expected health effect of CT-scans, stress is a powerful confounding factor, I would expect.

    • Rod Adams says:

      @Joris van Dorp

      I wonder if similar effects can be induced into a population of 94,000 people who were near an atomic bomb blast and have been told repeatedly during a period of more than 60 years that their experience has increased their risk of contracting cancer?

  9. Mohan Doss says:

    The NY Times Op-Ed “We are giving ourselves cancer” does not represent current state of knowledge in this field, and makes many misleading statements. I have presented a line-by-line criticism of the article in my blog which is available at:

    http://are-we-really-giving-ourselves-cancer.blogspot.com/

    CT scans are safe, and the present concerns regarding radiation dose from CT scans are not justified by any evidence.