Do CT Scans Cause Cancer?

by E. Stephen Amis, Jr., MD

The last several months have presented one worrisome story after another regarding the dangers of CT scans… including more than 200 patients receiving radiation overdoses while undergoing brain scans at a California hospital… unpredictable and widespread variation in radiation dosing for cardiac scans from one hospital to the next… and a new research report revealing that the cancer risk from radiation in a CT scan may be far higher than was thought. Two studies on this topic were published in the December 2009 issue of Archives of Internal Medicine. One of the studies reports that just one scan can deliver enough radiation to cause cancer and predicts that 29,000 new cancers will develop that can be linked to CT scans received in just the year 2007. Making matters much worse is the fact that the use of CT scans in medicine has grown explosively — more than tripling in the US since the 1990s, with more than 70 million given each year.

Where it was previously thought that only those who underwent numerous scans were in danger, the second of the published studies shows that having had even one can boost cancer risk notably — for example, a heart scan at age 40 would later result in cancer in one in 270 women and one in 600 men. Abdominal and pelvic CT scans raise the risk for cancer more than brain scans, and the risk is far greater in younger patients, especially children.

The same researchers also noted huge variability in how much radiation patients get, with some patients getting 10 or more times as much radiation as others. There are a variety of reasons for this, including equipment settings that aren’t standardized and the radiologist’s decision about how much is necessary to capture a high-quality image of a particular part of the body. Also, methods for reducing radiation, such as adjusting for the size of the patient, are underutilized. Yet another danger — when equipment is new and unfamiliar (as was the case with the California patients who received overdoses) and technicians aren’t properly trained, the patient may receive unintended excess radiation.

This is frightening stuff — but let’s put it in context. I called E. Stephen Amis, Jr., MD, chair of radiology at both the Albert Einstein College of Medicine and Montefiore Medical Center in the Bronx, New York, to get his thoughts on the risk versus reward and what people should do to protect themselves from the risks of radiation exposure in imaging procedures. He said it is important to realize that in many cases CT scan technology is truly “lifesaving” and that, when used properly, the benefits obtained by getting the comprehensive information on what’s currently wrong outweigh the future risks presented by the radiation. For instance, if you have suspected acute appendicitis or head trauma as a result of a car accident, your doctor needs to know that — fast. Dr. Amis also pointed out that no direct evidence shows particular cancers are related to CT scans — rather the relationship is “inferred, based on increased cancers in survivors of the atomic bombing of Japan and in those exposed to the fallout from Chernobyl (among others).”

What you need to know

The radiology community is working to get these problems under control. Meanwhile, however, it is not safe for each of us as patients to pretend these problems don’t exist while the system sorts itself out — at best, that will take years. It is important to take steps now to minimize your risk. Here is what you can do…

  • Keep notes on all the scans you’ve had that you can remember (ask family members if you are unsure), including the body area and type of scan (x-ray or CT). If you have a chronic condition, such as colitis or chronic lung disease, that necessitates multiple imaging procedures, ask your doctor about other imaging options that might be a good substitute for CT scans.
  • Carry records with you. Keep and update a wallet-sized card listing the imaging tests that you’ve had and where and when each was done. (Note: To download a form to record your imaging tests, go to or send a self-addressed, stamped business-sized envelope to “Daily Health News/Medical Imaging Record,” Box 10702, Stamford, Connecticut 06904-0702.)
  • If and when your doctor advises you to have a CT scan, ask lots of questions. This is particularly important for tests like cardiac CT scans that may not be strictly necessary, but that your doctor may order to gather more information about your overall health. Ask about the possibility of using alternative imaging methods, such as MRI or ultrasound, neither of which uses radiation. Dr. Amis suggests using language something like this: “I’ve seen a lot of articles lately about some of these tests increasing your radiation exposure. Please tell me what knowledge you hope to gain by having me go through this CT scan. Is this test really necessary?”
  • Be aware of dosages. Dr. Amis also advises asking about the radiation dosage required for the specific test your doctor has prescribed, noting that sites such as list typical doses, comparing exposures among various types of x-ray and CT examinations. “It never hurts for patients to look at such Web sites so that they are informed,” he said, advising asking the technician about the dose to be sure it is in a reasonable range.

The bottom line? Know the risks and be careful. As Dr. Amis told me, “the point is to be aware, but not overly concerned.”


E. Stephen Amis, Jr., MD, professor and university chair, department of radiology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York.