Can CT Scans Cause Cancer

[ghchealth]

What Is An Appropriate Response to the Dangers of CT Radiation?

Posted 02/14/2006 - Medscape

Richard C. Semelka, MD

"I have only been sued for not ordering a CT scan, never for ordering one. Currently, I am defending the decision not to order one to do a serial abdominal exam in 6 hours...1 or 2 more suits like this protecting [patients'/plaintiffs'] rights and I will be out of practice." - Emergency Doc

The prologue to this first Semelka's Spin column is the email above, which was received as a reaction to an article I developed for Medscape last year that was entitled "Radiation Risk From CT Scans: A Call for Patient-Focused Imaging"(see http://www.medscape.com/viewarticle/496297).

Unfortunately, this response reflects a few facets of human nature that are firmly entrenched and cannot be changed overnight; however, we can take small steps to achieve good medical practice while at the same time avoiding litigation.

There are a few truths of the modern medical environment that this email reveals:

Diagnostic imaging has become the modern physical exam;
The pressing immediacy of patients to be informed and have answers;
The short-sighted view of healthcare management;
The unacceptability of bad outcomes in medicine, despite the vagaries inherent in the practice of medicine; and
The litigious nature of modern society.
The sentiments in this email likely play out in every emergency department several times each day. As a result, many unnecessary computed tomographic (CT) studies are ordered. I am afraid, at the present time, that many physicians are responding to patients' demands for immediacy of health information and also their own fear of litigation.

The viewpoint of the public is fickle, so while at the present time patients are demanding more and more CT studies to evaluate every ache and pain, within a few years' time I believe amnesia will occur about these demands. Instead, we will be confronted by a hailstorm of litigation surrounding "Why did you order this unnecessary CT scan on me, which now has caused me cancer? You never told me that I could get cancer from this."

The appropriate action to this looming crisis is expanded knowledge and information. I believe that physicians should inform patients of the following key facts:

There are risks associated with undergoing a CT scan; the BEIR VII report, which was published by the largest scientific organization in the world, the National Academy of Sciences, has described a 1 in 1000 chance of developing cancer from a single radiation exposure of 10 mSv.[1] That exposure is equal to 1 CT study of the chest region, the abdominal region, or the pelvic region. It is up to each patient to decide whether the chance of having a particular disease that only a CT performed now could determine is much less likely than the chance of potentially being harmed by the CT.

A defense for this position is based on the BEIR VII report as well as articles written on excessive use of CT and potential harm that may arise from overutilization of the study.[1-5] Unnecessary use of CT should particularly be avoided in pediatric patients and in studies of the pelvis and thorax of women up to 40 years of age (at a minimum). CT performed in young women to investigate potential pulmonary embolism is an example of a study that has tremendous potential to do harm because of breast cancer induction.[6] Whenever possible, we should employ alternative, non-x-ray-based modalities, especially when these modalities are superior to CT. Liver imaging is a perfect example of this, as MRI is diagnostically superior to CT, in addition to being a safer study.

In summary, if we are sure that CT scans will not help to investigate the complaints of a patient, informing the patients of the risks of radiation and cancer (which we should do with everyone) explains to them why we do not feel a CT study is warranted. In addition, we feel that, in certain instances, CT scans have the potential to do more harm than good. The references cited in this article are the bare-bones proof of this, to be shared with your imaging and referring physician colleagues.

We also must seek out alternative technologies that are safer when they are diagnostically superior or equivalent. This will be an ongoing process. As a scientific community, we must respect the powerful information that CT has given us about disease, but we also must constantly ask ourselves whether MRI or ultrasound has improved to the level of giving us comparable diagnostic information while maintaining a high degree of patient safety.

Diagnostic accuracy and patient safety -- Primum non nocere.

References
Committee on the Biological Effects of Ionizing Radiation (BEIR V) NRC: Health Effects of Exposure to Low Levels of Ionizing Radiation: BEIR V. Washington, DC: National Academy Press; 1990.
Frush DP, Donnelly LF, Rosen NS. Computed tomography and radiation risks: what pediatric health care providers should know. Pediatrics. 2003;112:951-957. Abstract
Paterson A, Frush DP, Donnelly LF. Helical CT of the body: are settings adjusted for pediatric patients? AJR Am J Roentgenol. 2001;176:297-301.
Donnelly LF. Reducing radiation dose associated with pediatric CT by decreasing unnecessary examinations. Am J Roentgenol. 2005;184:655-657.
Partrick DA, Janik JE, Janik JS, Bensard DD, Karrer FM. Increased CT scan utilization does not improve the diagnostic accuracy of appendicitis in children. J Pediatr Surg. 2003;38:659-662. Abstract
Parker MS, Hui FK, Camacho MA, Chung JK, Broga DW, Sethi NN. Female breast radiation exposure during CT pulmonary angiography. Am J Roentgenol. 2005;185:1228-1233.

Richard C. Semelka, MD, Director of MR Services; Professor of Radiology; Vice Chairman of Clinical Research, Department of Radiology, University of North Carolina at Chapel Hill