The pattern of excess cancer risk may be partly due to confounding by indication.
Radiation doses from CT during childhood increases brain tumor risk, according to a study published in the Journal of the National Cancer Institute.
Researchers from the Netherlands performed a retrospective study to evaluate leukemia and brain tumor risk following exposure to low-dose ionizing radiation from CT scans in childhood.
The researchers reviewed data of 168,394 children who received one or more CT scans in a Dutch hospital between 1979 and 2012 who were younger than age 18 years. The researchers obtained cancer incidence, vital status, and confounder information by record linkage with external registries.
The results showed standardized incidence ratios were elevated for all cancer sites. Mean cumulative bone marrow doses were 9.5 mGy at the end of follow-up, and leukemia risk (excluding myelodysplastic syndrome) was not associated with cumulative bone marrow dose (44 cases). Cumulative brain dose was on average 38.5 mGy and was statistically significantly associated with risk for malignant and nonmalignant brain tumors combined. Excluding tuberous sclerosis complex patients did not substantially change the risk.
The researchers did caution, however, that the pattern of excess cancer risk may be partly due to confounding by indication, because the incidence of brain tumors was higher in the cohort than in the general population.
"Epidemiological studies of cancer risks from low doses of medical radiation are challenging,” principal investigator, Michael Hauptmann, Ph.D., from the Netherlands Cancer Institute, said in a release. "Nevertheless, our careful evaluation of the data and evidence from other studies indicate that CT-related radiation exposure increases brain tumor risk. Careful justification of pediatric CT scans and dose optimization, as done in many hospitals, are essential to minimize risks."