Uncertain Diagnosis or CT Scan Radiation? | Guest Blog

Which would you choose? When it comes to accuracy in diagnosis vs radiation-induced cancer risk, parents overwhelmingly choose the former.

It is so nice to be right.

To summarize what I wrote 2 and 3 years ago, here and here—based on my experience, patients and families will accept the theoretical risk of a future cancer if it means they’ll get an accurate diagnosis.

A new study validates that opinion.

MedPage Today reports that parents of 742 children who arrived at the emergency department with head injuries were surveyed by researchers from Toronto’s Hospital for Sick Children. The parents were queried before receiving any recommendation for CT scanning.

Parents, almost half of whom had previously known that CT scanning might cause a cancer to develop in the future, were told of the radiation risks of CT scanning in detail. The authors found that, although the parents’ willingness to go ahead with the CT scan fell from 90% before the explanation of risk to 70% after they were briefed about radiation, at crunch time only 42 (6%) of them refused to let their child be scanned.

And of the 42 who initially refused, 8 eventually went ahead with the scan after a physician recommended it.

So to put it another way: Even after they were fully informed of the potential risk of CT scan radiation to their child (lifetime risk of cancer is about 1 in 10,000, according to the authors), nearly all parents opted for the scan.

Also of note are the following: The median age of the children was 4; 12% of the children in the study had undergone at least one previous CT scan; 97% of the children were diagnosed with only concussions or mild head injuries.

An article in Scientific American puts some of the radiation risk into perspective. It is long, but worth reading — as it explains how risk has been calculated, the best guess as to the true level of risk, and what radiologists are doing to lower the radiation exposure associated with CT scanning.

According to that article, “Any one person in the U.S. has a 20% chance of dying from cancer [of any type]. Therefore, a single CT scan increases the average patient’s risk of developing a fatal tumor from 20 to 20.05%.”

I agree that CT scans should be ordered judiciously. The area scanned and the amount of radiation should be limited as much as possible.

But if you need a CT scan to help diagnose your problem, go ahead and have it. As pediatric intensivist Dr. Christopher Johnson said on the KevinMD website, “Respect diagnostic radiation but don’t have an irrational fear of it.”

Bottom line: When it comes to accuracy in diagnosis vs radiation-induced cancer risk, parents overwhelmingly chose the former.

Skeptical Scalpel is a recently retired surgeon and was a surgical department chairman and residency program director for many years. He is board-certified in general surgery and a surgical sub-specialty and has re-certified in both several times. For the last two years, he has been blogging at SkepticalScalpel.blogspot.com and tweeting as @SkepticScalpel. His blog averages over 900 page views per day, and he has over 6,300 followers on Twitter.

  • Tae says:

    What the article’s really saying is that most parents will do what the physician recommends that they do, despite other fears they may have (“The authors found that, although the parents’ willingness to go ahead with the CT scan fell from 90% before the explanation of risk to 70% after they were briefed about radiation, at crunch time only 42 [6%] of them refused to let their child be scanned. And of the 42 who initially refused, 8 eventually went ahead with the scan after a physician recommended it”).

    Look – we’re primates with huge visual cortices, we love diagnostic imaging for that reason, but we certainly don’t use it in a rational fashion, assuming instead that these studies (as good as they are) are both 100% sensitive and 100% specific, at all times and in all patients. We forget (or ignore) that these studies, and any diagnostic testing, has limitations in both their ability to rule out and rule in pathology which results in a subsequent cognitive bias.

    Sure, the risk of cancer from radiation may be low, but the real problem may be in the way our diagnostic approaches bias our decision making.

    • SkepticalScalpel says:

      Tae, thanks for the comments. I understand you points. The problem is we are where we are. The public has been indoctrinated. They want accurate diagnoses. They want tests. I think the only solution short of massive re-education of the public, which is unlikely, is to reduce the radiation exposure as much as possible.

      • Tae says:

        Thank you for the reply, and likewise, I understand your points! It’s not only the public, health care professionals have also been indoctrinated with these ideas and expectations. I’ve had nurses and physicians as patients request/demand CTs for “peace of mind” despite extended discussions about the best evidence. I appreciate and agree with your harm-reduction approach (“reduce the radiation exposure as much as possible”), but the quixotic educator in me can’t help but also feel the need to press the discussion, with individual patients, other health care professionals, and the public as a whole.

        • SkepticalScalpel says:

          As I said in a post a while back, it is hard to talk people out of having a study once they have it in their minds that a study is needed. Many docs just don’t have the time. Also, what happens if the study is not done and a complication occurs? There are lots of lawyers waiting to pounce.

  • VL says:

    “According to that article, “Any one person in the U.S. has a 20% chance of dying from cancer [of any type]. Therefore, a single CT scan increases the average patient’s risk of developing a fatal tumor from 20 to 20.05%.”

    Should not the risk be 20.01% and not 20.05% if the incremental cancer is 1 in 10,000

    • SkepticalScalpel says:

      From page 2 of the Scientific American article which I linked to in my post:

      “Based on such data, a 2006 report from the National Research Council has estimated that exposure to 10 mSv—the approximate dose from a CT scan of the abdomen—increases the lifetime risk of developing any cancer by 0.1 percent. Using the same basic information, the U.S. Food and Drug Administration concluded that 10 mSv increases the risk of a fatal cancer by 0.05 percent. Because these risks are tiny compared with the natural incidence of cancer in the general population, they do not seem alarming. Any one person in the U.S. has a 20 percent chance of dying from cancer. Therefore, a single CT scan increases the average patient’s risk of developing a fatal tumor from 20 to 20.05 percent.”

  • joedrman says:

    CT Scans are not just ordered willy nilly, especially of the brain. For a head trauma patient this is the best course of action to find a bleed. An Xray or MRI only shows structural compenents not a significant bleed. So, hence the necessity for a Brain CT to rule out a Subarachnoid hemorrhage, parenchymal hemorrhage, or aneursym.

    In a recent new article published by FoxNews states that “One recent study found that for every 10,000 children under age 10 that have a scan, one additional child will develop cancer in the next decade.” This is such an inaccurate statement, one cannot say for certain this will happen. Many factors come into play such as genetics, environment, and exposures. To state there is a probabilty is more believable, and a truer statement.
    Read more: http://www.foxnews.com/health/2013/07/17/half-parents-aware-ct-scan-risks/#ixzz2czkJz76a

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