Children and adolescents who undergo a diagnostic computed tomography (CT) scan are 24% more likely to develop cancer in their lifetimes than patients who do not receive the testing, new research has found.
In the largest-ever population-based study of exposure to low-dose ionizing radiation from diagnostic computed tomography (CT) scans, Australian researchers found that children and adolescents who undergo a CT scan are 24% more likely to develop cancer in their lifetimes than patients who do not receive the testing.
Investigators derived direct estimates of the increased risk for cancer in the first decade following CT exposure by comparing incidence of cancer in 680,000 patients aged 0 to 19 years who received a CT scan at least 1 year before cancer diagnosis with a comparison group who were never exposed. Participants were born between January 1, 1985, and December 31, 2005. Mean duration of follow-up was 9.5 years for the exposed group and 17.3 years for the unexposed group. Eighteen percent of the exposed group had received more than 1 CT scan.
After adjusting for age, sex, and year of birth, overall cancer incidence was 24% greater for the exposed group versus the unexposed group. The incidence rate ratio was greater for persons exposed at younger ages: at 1 to 4 years, 5 to 9 years, 10 to 15 years, and 15 or more years, the ratios were 1.35, 1.25, 1.14, and 1.24, respectively. The risk increased by 16% for each additional CT scan.
The researchers say their findings are consistent with the theory that for CT imaging “there is no threshold dose below which there is a zero risk.” Although the overall risk for cancer is low (9.38 for every 100,000 person years of follow-up), their findings justify concerns about radiation exposure from CT scans in childhood and adolescence and also about the lifetime risk from additional CT scans in adult life.
They recommend that practitioners carefully weigh the benefits of CT scans against the potential risks and limit CT scans for children to those situations for which there are definite clinical indications. In addition, radiologists must ensure that diagnostic scanning in children is performed at the lowest possible radiation dose.