CT scans may give cancer to one in 80 patients, says new research

Published on Monday 14 December 2009 21:35

CT SCANS may pose a much bigger radiation danger to patients than is generally believed, research has shown.

Some scans may be triggering cancer in as many as one in 80 patients, say US scientists.

Such a level of risk is far higher than the one in 1,000 odds that are generally quoted. If the American findings hold true for the UK it could mean the X-ray procedures are causing thousands more cases of cancer than is suggested by current estimates. CT, or Computed Tomography, scans take cross sectional X-rays to build up detailed 3D pictures of internal organs, blood vessels, bones or tumours. All X-rays are associated with a slim increased risk of cancer.

Results of the US study published in the journal Archives of Internal Medicine showed

that, for individual types of scan, there was an average 13-fold variation between the highest and lowest doses experienced by patients.

"If a physician sent a patient for a particular CT procedure, the dose that patient would have received varied by this much," said study leader Professor Rebecca Smith-Bindman, from the University of California at San Francisco.

"The risk associated with obtaining a CT is routinely quoted as around one in 1,000 patients who undergo CT will get cancer. In our study, the risk of getting cancer in certain groups of patients for certain kinds of scans was as high as one in 80."

The typical effective dose delivered by a single CT scan was the equivalent of up to 74 mammograms or 442 chest X-rays, said Prof Smith-Bindman.

A separate team of scientists writing in the same journal calculated that around 29,000 cancers in the US could be related to CT scans performed in 2007.

Two-thirds of the predicted cancers would occur in women, who are more sensitive than men to the effects of radiation.