Too Much Radiation From Full-Body CT Scans?
Repeat Full-Body CT Scans May Raise Cancer Risk
Aug. 31, 2004 -- They promise to cut your risk of dying from cancer. Yet full-body CT scans themselves pose a real cancer risk, new calculations suggest.
X-rays from a single full-body CT scan give a dose of radiation similar to cancer-associated radiation doses in A-bomb survivors, finds David J. Brenner, PhD, director of Columbia University's center for radiological research.
It's not a huge risk, especially for someone with symptoms of a dangerous condition. But when used to screen healthy people for hidden evidence of disease, the risk may outweigh the benefit. And if a healthy person gets repeated full-body scans, cancer risks multiply, Brenner and colleague Carl D. Elliston report in the September issue of Radiology.
"The risks from a single full-body CT scan are not large: If 1,200 45-year-old people got one, you might expect one to die from radiation-induced cancer," Brenner tells WebMD. "But if you are thinking of doing this on a regular basis, as a routine screening modality, then the radiation doses start to add up and the risks then start to get quite high."
A single full-body CT scan gives a person a total radiation dose of about 12 mSv. That's close to the 20-mSv dose linked to cancer in Japanese survivors of atomic bombs. And each of these scans adds another 12 mSv to a person's total lifetime exposure. An mSv is a unit for measuring radiation dose.
Studies suggest that full-body CT scans aren't likely to benefit anybody under the age of 45. This led Brenner to calculate cancer risk for someone who decided to have annual full-body CT scans beginning at that time.
"If you start at age 45, and have them annually until you are 75, you are talking about a one-in-50 chance of radiation-induced cancer, which is a huge risk," Brenner says. "Until the benefit is clear, there is not much of an advantage to having routine body scans yearly or even every two years. But a single scan is not much of an issue."
For several years now, freestanding clinics have been offering full-body CT scans to anyone who wants one. Ads for the clinics promise early detection of dangerous diseases such as cancer and heart disease. The idea is that full-body CT scans will find tumors other signs of disease in their earliest, most treatable stages -- before a person has any symptoms of illness.