Full-body CT Screening for Healthy Adults May Slightly Increase Risk of Cancer Mortality
Computed tomography (CT or CAT) scans give physicians a look inside the body with no pain to the patient. Using x-ray technology, a CT scan creates detailed pictures of body tissues. The patient lies on a table that is moved in and out of the CT machine—a large square machine with a hole in the middle. Small beams of radiation are passed through various parts of the body and collected on the other side. Each beam represents a bit of data that are combined by a computer to generate images of inside of the body. CT scans are used to diagnose a variety of medical conditions, including cardiovascular diseases, cancer, infectious diseases, trauma, and musculoskeletal disorders.
CT scans are traditionally used for sick or symptomatic people to help make a diagnosis. However, there is a recent rise in the use of full-body CT scanning to check healthy adults for early signs of disease. While the value of CT for diagnosis is clearly established, there are no scientific studies to show that full-body CT scanning to screen healthy adults is beneficial. Proponents of CT scanning for early detection recommend having scans yearly. Some critics of this practice point to the risk of false-positive findings, which can lead to unnecessary testing, stress, and expense.
A CT scan delivers higher doses of radiation than other x-rays studies. Compared with a mammogram, for example, the CT machine delivers 100 times as much radiation. While one CT scan on an isolated part of the body raises no concerns, repeated total body scans may delivery enough radiation over time to be harmful. Researchers from the Center for Radiological Research at Columbia University in New York took a closer look at this concern. Using data from atomic bomb survivors, the researchers estimated the increased risk of cancer deaths associated with exposure to radiation via CT scanning. Their findings, published in the September issue of Radiology , showed increased risks that should be a factor when considering the risks and benefits of total body screening CT scans.
About the study
The researchers estimated the dose of radiation exposure from a single full-body CT scan, based on a protocol developed at Johns Hopkins Hospital. Next, they compared these doses to those received by the atomic-bomb (a-bomb) survivors in Hiroshima and Nagasaki—a group known to have increased rates of cancer mortality. The dose from a single full-body CT scan is within the same range as doses that are known to have increased the risk of cancer among the a-bomb survivors. Using this data, the researchers estimated the percent increases in cancer risk due to single and multiple CT scans in different age groups.
The researchers’ estimations showed that the lifetime risk of cancer death increases after just one CT scan and grows with each successive scan. For example, a single full-body CT scan in a 45-year-old results in a one in 1,250, or 0.08%, increased chance of dying from cancer. This risk jumps to one in 50, or 1.9%, for an adult who begins having scans at 45 and has one each year for 30 years. This study also found that radiation-induced lung cancer was the main form of cancer associated with CT scans.
How does this affect you?
Do these findings cast doubt on the safety and utility of CT scanning for the diagnosis of disease? Absolutely not. If your physician recommends a CT to help determine the cause of symptoms, the benefits of this test far outweigh the risks. It is the practice of conducting scans on healthy people to detect early stages of disease that is called into question by this study. And particularly questionable is the practice of having scans on a regular basis. Although the idea of a painless scan to screen for disease sounds appealing, there is no scientific evidence to show these scans can affect disease progression or death rates. The risk of false positives has already been identified.
This study adds a new factor to the risk/benefit equation—the unnecessary exposure to radiation that increases the risk of dying from cancer. It is hard to justify even a slight increase in risk if there is no clear benefit. If you would like to use CT scanning to screen for disease, discuss your personal risk factors with your doctor. Based on the findings of this study, repeated total body CT scans may not be in your best interest.
The American College of Radiology & the Radiological Society of North America
National Cancer Institute
The American College of Radiology & the Radiological Society of North America. Computed tomography (CT) – Body. Available at: http://www.radiologyinfo.org/content/ct_of_the_body.htm Accessed August 31, 2004.
Brenner DJ, Elliston CD. Estimated radiation risks potentially associated with full-body CT screening. Radiology . 2004;232:735-738.
National Cancer Institute. Computed tomography (CT): questions and answers. Available at: http://cis.nci.nih.gov/fact/5_2.htm Accessed August 31, 2004.
Radiological Society of North America. Full-body CT screening increases risk of cancer death. [Press release]. Available at: http://www2.rsna.org/pr/target.cfm?ID=200 Accessed August 31, 2004.
Last reviewed Sep 3, 2004 by
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