The Unrecognized Risks of CT Radiation

by: Devra Lee Davis, PhD, MPH, Director, Center for Environmental Oncology of UPCI.
Adapted from The Secret History of the War on Cancer.

Diagnostic radiation is a modern miracle we have come to depend on. In 1979, The Nobel Prize in Medicine and Physiology was awarded to Godfrey N. Hounsfield and Allen M. Cormack, the engineer and physicist who invented the system for creating three-dimensional images of the human body. Computerized imaging technology is now such a large, profitable industry that it has its own futures market. Seven times more CT scans are conducted today than just ten years ago.(1) The leading manufacturer, Cardinal Health, is one of the twenty largest companies in the world, with revenues of more than $87 billion a year.(2)

New government regulations in the United States are shutting down what had been highly profitable ventures in which physicians would prescribe tests on machines they themselves owned. When offered a three-dimensional look inside an old set of knees or cranky stomach, a patient does not usually ask whether this remarkable test might increase her long-term risk of more serious ailments.

When my then eleven-year-old daughter was given a CT scan of her abdomen to see if she had a ruptured spleen, I was just like most parents with a child in the emergency room. All I wanted to know was that she would be okay. But when I asked the young radiologist if there was a way to shield my daughter's chest, she looked at me skeptically and asked, "Why? She doesn't have any breasts." I explained to her that we know that radiation exposure to the chests of girls before puberty increases the chances that breast cancer will develop later on. The woman looked at me as if I were slightly insane.

My colleague Dr. Dwight Heron, Vice Chairman for Clinical Affairs, Department of Radiology, University of Pittsburgh Cancer Institute and Chairman, Department of Radiation Oncology, UPMC Shadyside, spends his days diagnosing and treating cancer patients with the help of modern computerized diagnostic scanning systems. I asked him what he thought about the current enthusiasm for CT and PET scans of healthy people.

Heron says, "It's a big problem. Radiologists appreciate that we could be creating more cancer in young people by what happens in emergency rooms all over the country today."

Heron referred me to the 2007 white paper on radiation in medicine, where the American College of Radiology (ACR) noted that in the past quarter century, the amount of radiation the U.S. population receives each year from medical imaging has increased fivefold. A single computerized scan of the stomach today can give half the dose that was shown to induce cancer in those who survived the atomic bomb blasts in Japan. The ACR advises that "the current annual collective dose estimate from medical exposure in the United States has been calculated as roughly equivalent to the total worldwide collective dose generated by the nuclear catastrophe at Chernobyl."(3)

Let me translate this. Modern America's annual exposure to radiation from diagnostic machines is equal to that released by a nuclear accident that spewed the equivalent of hundreds of Hiroshimas across much of Russia and Eastern Europe. In 2005, the Chernobyl Forum, an organization led by the International Atomic Energy Agency and the World Health Organization, estimated that about 6.5 million people were exposed to 5.6 Roentgen per second (R/s). This is equivalent to 20,000 Roentgen per hour (R/h). A lethal dose is around 500 Roentgen over five hours, so in some areas, unprotected workers received fatal doses within several minutes of radiation from the Chernobyl explosion in 1986. Conservative estimates are that as a result of this massive explosion there will be 30,000 to 60,000 more cancer deaths that would not otherwise have occurred. (4)

Concerns about unnecessary medical radiation in young children today are now ricocheting throughout the medical community. A group of Yale researchers, looking at current patterns, estimates that in one year, 700 people will die from cancers associated with head CTs and 1,800 will die from radiation-induced cancer from abdominal examinations carried out when they were infants. (5) Reduced brain function, learning problems and lowered IQ from such potentially unnecessary and inappropriate exams is not easily calculated, but it cannot be trivial.(6)

Most physicians and the rest of us are unaware of the dangers shown in Table 15-2 (see below)

To put these doses into perspective, even a properly calibrated CT scan of a child's stomach can be equivalent to six hundred chest X-rays, while one of an infant's head can be equivalent to a few thousand. Imagine a lifetime of emergency room visits, with repeated scans, and it becomes clear that these risks could create a major cancer burden of the future.

Emergency room physicians have not yet gotten the message. A survey of emergency room doctors at a major medical center found that none of them was aware that some of the diagnostic procedures they were ordering increased the risk of cancer for their patients thirty years later.

Of the more than 10 million cancer survivors in this nation, those who underwent extensive radiation to treat or find their disease, like Elizabeth Edwards, wife of Sen. John Edwards, and Tony Snow, former press secretary to the White House, or those who had the disease as young children, face lifetime risks of other cancers as a result. Other studies show that the risks of cancer from radiation in cancer patients treated for Hodgkin's disease could even be greater than those of the atom bomb survivors. This apparently greater vulnerability of the weakened to the damaging effects of radiation is something that researchers like Alice Stewart and Rosalie Bertell warned about nearly half a century ago. (7) The world is catching up with them.

Stewart's work on the dangers of radiation in England was simple and powerful. She visited every county and county borough health department in the country, handing out questionnaires that asked mothers of children born between 1953 and 1955 about things that happened to them when they were pregnant. Within a year, she had determined that the mothers of leukemic children were three times more likely to have had routine x-rays of their abdomens during pregnancy. These results, published in the Lancet in 1956, flew in the face of assurances from obstetricians that the practice was harmless. Stewart's findings also upset those advocating the continued use of nuclear weapons and testing. The year 1956 was the peak year for above-ground nuclear weapons and testing and radioactive fallout. Obstetricians and nuclear weapons advocates alike maintained that small doses of radiation were harmless. In fact, Stewart's findings showed that a single dose of diagnostic x-rays early in pregnancy more than doubled the child's risk of leukemia. (8)

There is no question that in medical emergencies, CT scans save lives and eliminate exploratory surgery. But, experts increasingly agree (see sidebar) that the number of scans can be reduced without compromising the ability to deliver health care. For healthy individuals, and especially children, if a CT scan is recommended, it is important to consider whether another diagnostic tool, such as Magnetic Resonance Imaging or ultrasound, neither of which involves radiation, could be used instead.

References

1. Janette Sherman, interview by author, December 11, 2006.
2. Cardinal Health. Facts. Accessed 2008 Feb. 14.
3. Amis ES Jr, Butler PF, Applegate KE, Birnbaum SB, Brateman LF, Hevezi JM, Mettler FA, Morin RL, Pentecost MJ, Smith GG, et al. 2007. American College of Radiology white paper on radiation dose in medicine. Journal of the American College of Radiology 4(5): 272-84.
4. Medvedev ZA. 1990. The legacy of Chernobyl. New York: W.W. Norton.

5. Brenner D, Elliston C, Hall E, Berdon W. 2001. Estimated risks of radiation-induced fatal cancer from pediatric CT. American Journal of Roentgenology 176(2): 289-96.

   See also
   Brenner DJ and Hall EJ. 2007. Computed tomography -- an increasing source of radiation exposure. The New England Journal of Medicine 357(22): 2277-84
   Bertell R, Ehrle LH, Schmitz-Feuerhake I. 2007. Pediatric CT research elevates public health concerns: Low-dose radiation issues are highly politicized. International Journal of Health Services 37(3): 419-39.

6. Rabin RC. 2007. With rise in radiation exposure, experts urge caution on tests. The New York Times; ScienceTuesday: F5 (June 19).
7. Richmond C. 2002. Alice Mary Stewart. BMJ 325(7355): 106.
8. Giles D, Hewitt D, Stewart A, Webb J. 1956. Malignant disease in childhood and diagnostic irradiation in utero. Lancet 271(6940): 447.