You’ve seen the full-page ads. Dozens of clinics nationwide are touting a new service for health-conscious people: full-body CT scans—high-tech computerized X-rays that promise early warnings for cancer, cardiac disease, and other abnormalities.
But these body scans are controversial because the long-term benefits and risks have not been researched. The Food and Drug Administration has approved the CT X-ray system only as a diagnostic tool to be used when symptoms exist, or when there is reason for further testing. But no studies have been done to support using CT scans for screening people without symptoms, or when there is no suspicion or indication of a problem or disease.
|This is a portion of an ad from a hospital that solicits people over age 40 to undergo whole-body CT screening at a cost of $499. The solicitation fails to reveal that the test has not been proven to do more good than harm. Some facilities charge more than $1000. At least one is promoting abdominal screening with warnings that only about a third of colon cancer patients have been diagnosed early. This sales pitch is misleading because many more cases would be detected if more people underwent the proven tests (fecal blood test, rectal exam, and sigmoidoscopy or colonoscopy) that would have a much higher yield than CT scanning. Other providers adescribe how people had their cancer discovered earlier. Such stories fail to reveal that many (and perhaps most) of these cancers would have been detectable by standard means and that most people who have the test will waste money. —Stephen Barrett, MD, March 9, 2002.||
Thomas B. Shope, Ph.D., a radiation physicist in the FDA’s Center for Devices and Radiological Health, says the agency’s concern is that “some of the kinds of things screening CT may find are not necessarily of any health significance.” In addition, because no screening test is 100% accurate, the FDA is concerned that many people will get false-positive results, leading them to seek additional, possibly risky tests or surgical procedures. While there is a small danger of this when symptoms exist, its occurrence is far more probable when they do not. Further, the use of any X-ray imaging procedure is always accompanied by a concern about the possible effects of radiation exposure.
“The effective dose from a CT procedure can be hundreds of times larger than the effective dose from a conventional radiographic procedure,” says Shope.
During a CT scan, an X-ray tube housed inside a doughnut-shaped machine rotates around and transmits radiation through a person’s body at various angles. Detectors inside the machine measure the radiation transmitted through the body and these data are converted into electrical signals. A computer gathers these signals and produces three-dimensional images that are displayed on a monitor. A technologist or radiologist can change the contrast or brightness of the displayed image, or use other image processing or display techniques to emphasize areas or tissues of interest.
Using CT systems for diagnosis in medicine has been accepted as a valuable medical practice based on a wealth of experience. And physicians may use it for any condition or disease, as long as they deem the use legitimate within the doctor-patient relationship. Therefore, although the device was approved as a diagnostic tool for specific purposes, the FDA has limited authority to control how it is actually used. The agency continues to approve CT systems and their enhancements on the basis that they are to be used in the diagnoses of symptomatic people.
The American College of Radiology “does not believe there is sufficient scientific evidence to justify recommending total body computed tomographic (CT) screening for patients with no symptoms or a family history suggesting disease.” The organization says there is no evidence that the procedure is either cost-effective, or effective in prolonging life. [In a statement approved by the ACR Board of Chancellors on September 27, 2000, the ACR also expressed concern that “this procedure will lead to the discovery of numerous findings that will not ultimately affect patients’ health, but will result in increased patient anxiety, unnecessary follow-up examinations and treatments and wasted expense.”]
Robert Smith, director of cancer screening at the American Cancer Society, says his organization also “discourages full-body scanning” for the same reasons.
For Additional Information
- FDA page on whole-body scanning
- American College of Cardiology/American Heart Association consensus statement
- New South Wales requires independent referral and informed consent
This article, which was published in the November-December 2002 issue of FDA Consumer magazine, has been modified by adding the advertisement, the accompanying comments, and the bracketed sentence in the paragraph about the ACR position statement.
This article was revised on June 20, 2003.