"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."The idea is to replace annual physicals with this noninvasive
test, which might detect things you wouldnt usually see -- like a small tumor, or
the beginnings of heart disease," he says. "It has the potential for seeing
things -- mainly cancers -- rather earlier than they might otherwise have been
James P. Borgstede, MD, chairman of the American College of Radiology's board of
chancellors, notes that the ACR does not sanction the use of full-body CT scans for
screening healthy people. He notes, however, that the ACR doesn't censure doctors who
perform the procedure.
"I think the people who get these scans are the worried well," Borgstede tells
WebMD. "They are very concerned about health but tend to be very safe, low-risk
people. They think they will live longer or have a better-quality life if they get these
scans, I guess. But there is no data that support they will live longer or better if they
have one of these exams."
Richard L. Morin, PhD, chairman of the ACR's commission on medical physics, says that
given lack of an established benefit, the risks Brenner identifies raise doubts about
screening healthy people with full-body CT scans.
"This paper is important in demonstrating explicitly that the risk from whole-body CT
or any other diagnostic radiology exam is not zero," Morin tells WebMD. "It
supports the thinking that screening whole-body CT scans of healthy individuals is not a
wise course of action."
Borgstede and Morin note, however, that the risk/benefit equation changes for patients
with symptoms who need CT scans to help diagnose a disease. These patients' symptoms
usually tell the doctor that a particular part of the body should be scanned. Full-body
scans, Borgstede says, usually aren't needed.
"We support clinical trials of CT screening for lung and colon cancer -- but those
are studies of selected populations we think may be at risk of very serious disease,"
he says. "That is different from screening the whole population from head to toe.
These screenings are planned only for the body area at risk."