Search Here

Computed tomography or CT scans are a great medical advancement and provides a variety of benefits like helping diagnose infections and tumors and guiding doctors to the right area during surgery. However, a new study reveals that the benefits of the scans do not come without risks. 

Previous studies have suggested that the radiation in imaging tests increase the risk of developing cancer, but so far nothing has been clearly defined. A new study, published Tuesday in the British Medical Journal, found that children and adolescents who had at least one CT scan were 24 percent more likely than kids who never had the scans to develop cancer. To put the findings into perspective, researchers explained that in a group of 10,000 young people, they would expect 39 cancers to occur during the next decade.  However, if the 10,000 young people all had one CT scan, researchers believe up to six extra cancers would occur.

Lead author Dr. John D. Matthews, of the School of Population and Global Health at the University of Melbourne in Carlton, Australia, looked at Australian Medicare and national cancer records of 10.9 million people between the ages of 0 to 19 years old.  All participants were born between 1985 and 2005 with total follow-up ending at the end of 2007.

Researchers said that of this group, 680,211 had a CT scan at least one year before a cancer diagnosis and 122,500 had received more than one scan.

Researchers followed participants who had undergone CT scans for an average of 9.5 years and those who never got scanned for just over 17 years.

The study revealed that 3,150 (.004 percent) of kids exposed to CT scans had developed cancer by the end of 2007.  Researchers said that this incidence rate was 24 percent greater in the exposed group after adjusting for age, sex and year of birth.  Researchers found that the risk increased by 16 percent for each additional CT scan.

The cancers in the study included tumors of the brain, digestive organs, soft tissue, female genital, urinary tract and thyroid along with melanoma and blood cancers. Researchers found that brain cancer risks were still significantly higher 15 years after the first CT scan, and the highest risks for brain cancer were seen in children who had their first CT scan before they turned five.

Solid cancer cases other than brain cancer increased over time since the first exposure, and girls were found to have greater increased risk than boys with 23 percent of females developing cancer compared to 14 percent of males.  Researchers found that increased risks for all cancers declined over time, but were still significantly higher than risks of people who had not been exposed to CT scans.

However, researchers said that almost 60 percent of CT scans were of the brain and recognize that in some cases the brain cancer may have led to the scan rather than vice versa.

Researches added that they "cannot assume that all the excess cancers [...] were caused by CT scans" and they "cannot rule out the possibility of some reverse causation, particularly for some cases of brain cancer".

However, they conclude that the "increased incidence of many different types of cancer [...] is mostly due to irradiation". They noted that because cancer excess was still continuing after follow-up, they could not determine the "eventual lifetime risk from CT scans".  They recommend that doctors weight the benefits against the potential risks to justify each CT scan.