Currently some medical imaging facilities are promoting a new use of computed tomography (CT), also called computerized axial tomography (CAT) scanning. This use is referred to as whole-body CT scanning or whole-body CT screening, and it is marketed as a preventive or proactive healthcare measure to healthy individuals who have no symptoms or suspicion of disease. At this time the FDA knows of no data demonstrating that whole-body CT screening is effective in detecting any particular disease early enough for the disease to be managed, treated, or cured and advantageously spare a person at least some of the detriment associated with serious illness or premature death. Any such presumed benefit of whole-body CT screening is currently uncertain, and such benefit may not be great enough to offset the potential harms such screening could cause. Public health agencies and national medical societies-the American College of Radiology, the American College of Cardiology, the American Association of Physicists in Medicine, and the American Heart Association -do not recommend CT screening.
CT is a diagnostic imaging procedure that uses x rays to obtain cross-sectional images of the body. Since its introduction and rapid adoption into medicine in the mid-1970s, CT has become recognized as a valuable medical tool for the diagnosis of disease, trauma, or abnormality and for planning, guiding, and monitoring therapy.
Important information regarding whole-body CT screening:
- Such screening provides uncertain benefit with potential for some risk: The most likely outcomes of CT screening of a healthy person with no symptoms of illness are:
- Normal findings or
- Suspicious findings requiring follow-up tests
Normal findings carry the possibility of inaccuracy and false reassurance. For suspicious findings, follow-up may involve simple, non-invasive testing. It may also involve invasive procedures associated with surgical risks of anesthesia, bleeding, infection, scarring, or it may entail additional radiological exams, associated with radiation risk and the potential risk of allergic reaction to injected contrast material. In any case, it is unlikely that CT screening will benefit an individual lacking signs or symptoms of disease by detecting a serious disease early enough to treat it and alter the outcome significantly.
- Radiation Dose: CT screening subjects the individual screened to radiation exposure from x rays. The dose a patient receives during a typical CT procedure is generally much larger than the radiation doses associated with most conventional x-ray imaging procedures. The principal risk associated with the radiation dose resulting to a person from a CT procedure is the small possibility of developing a radiation-induced cancer some time later in that person's life. For a patient with a medical need, the benefit of a diagnostic or therapeutic CT procedure recommended by a physician normally far exceeds the small cancer risk associated with a CT procedure. For a person without symptoms, CT screening is unlikely to discover serious disease, and the potential harm to the individual may be greater than the presumed benefit.
- Scientific Studies: There are no data demonstrating that whole-body CT screening of individuals without symptoms provides a greater probability of benefit than harm. Nor is there any scientific study known to be underway to develop such data. Although there are several ongoing investigational studies of the effectiveness of using CT to screen people, the studies are focused on high-risk groups for specific diseases (e.g., cigarette smokers for lung cancer). In such studies only a limited portion of the body is irradiated, not the whole body, and only screening for a specific type of disease is being evaluated, rather than screening for just anything that might be found anywhere in the body.
- No Food and Drug Administration (FDA) Approval of CT for Screening: Statements by CT imaging facilities that imply FDA "approval," "clearance," or "certification" of CT for screening procedures misrepresent the actual situation. FDA has never approved or cleared or certified any CT system specifically for use in screening (i.e., of individuals without symptoms), because no manufacturer has ever demonstrated to the FDA that their CT scanner is effective for screening for any disease or condition.
No screening indication approved: CT systems were manufactured and marketed for diagnostic use prior to the 1976 Medical Device Amendments and were placed in Class II based on the level of risk they present. These devices continue to be cleared for marketing for general imaging purposes. No data have been presented to the FDA to demonstrate that these devices are effective for screening, i.e., testing individuals without symptoms. Before FDA would allow such a claim or indication for use by the manufacturer, the manufacturer would have to provide valid scientific data for such a new use by submitting a premarket approval application for this new indication. This means that manufacturers of CT imaging systems cannot make claims that the products are intended to be used for screening non symptomatic individuals. Nevertheless, individual physicians may decide that a patient without symptoms can benefit from screening with CT even though data supporting such a use has not been submitted to the agency. Such use of a medical device is referred to as "off-label" use and is a judgment left to physicians. However, statements that say or imply that FDA has approved CT scanning for whole-body screening uses are not correct.
For more, please visit the Computerized Axial Tomography (CAT Scan/CT Scan) Center.
This information has been provided with the kind permission of the FDA (www.fda.gov).