CT Scan Exposure Causes Small Increase in Cancer Risk for Kids, Adolescents

Children and young adults who have been exposed to CT scans have a small increased risk of developing cancer, according to a finding reported in the journal BMJ.

The study, which was led by professor John Mathews at the University of Melbourne in Australia, found that there was a confirmed small increase of cancer risk for children and adolescents who were exposed to CT scans. Researchers say that the risk should be considered against the undoubted advantage CT scans offer in terms of diagnosing and monitoring health conditions.

The study alerts doctors to opt for a CT scan only when a definite medical reason exists. In addition, they should insist on the use of the lowest possible X-ray dose for CT scans.

"As an individual patient, your risk of cancer from a CT scan is very low. In the vast majority of cases the benefits of a CT scan in diagnosing a condition or guiding treatment will outweigh the risks. Nevertheless, it is clear from our study that it is important for doctors to use CT scans only where they are necessary. By reducing the number of scans performed in a large population, there will be a small but corresponding reduction in the number of cancers in later years," Mathews said in a press statement.

It is a known fact that an extra dose of radiation damages the DNA and elevates the risk of cancer. Since the radiation doses from CT scans are small, it is uncertain whether such small doses can cause cancer. To answer this question, the study linked anonymized Medicare records of CT exposures for the entire population of young Australians, aged 0-19 years between 1985 and 2005, to cancers diagnosed up to the end of 2007.

The researchers noticed that for every 1,400 CT scans conducted before the age of 20, there existed one additional case of cancer over the following 10 years.

The risk of being diagnosed with cancer increased with the number of CT scans. Compared to teenagers, young children had a higher proportional increase in risk of cancer after a CT scan. 

Though the study was conducted exclusively on children and adolescents, researchers feel that grown-ups could face a risk from CT scans as well.