Risk of childhood brain tumors after exposure to CT radiation: A nationwide population-based case-control study in Finland.

In this nationwide population-based case-control study, we assessed the risk of childhood brain tumors following exposure to radiation from CT. Brain tumors diagnosed in Finland during 1990-2016 were identified by the Finnish Cancer Registry. For each case, three age- and sex-matched controls were sampled from the Population Information System. The study population was linked to a CT dataset encompassing pediatric CTs performed in Finland during 1975-2011. We implemented a 5-year lag period and excluded participants with cancer predisposition syndromes or previous malignancies. We estimated brain doses using the NCICT program. Overall, 1067 brain tumors were diagnosed in children aged 0-15 years during 1990-2016, 58% of which were gliomas. Among eligible participants, nine cases (1%) and 10 controls (0.4%) had undergone at least one head/neck CT scan. The mean cumulative brain dose was 22 mGy for exposed participants. Participants who had undergone one or more head/neck CTs had a higher risk of developing brain tumors compared to unexposed individuals (Odds ratio [OR] = 2.84, 95% CI 1.12, 7.19). The excess OR (EOR) per 100 mGy of brain dose was 5.50 (95% CI 0.31, 10.95) for all brain tumors, and 1.06 (95% CI -6.55, 9.30) for gliomas. Our results suggest a positive association between head/neck CT imaging and the risk of childhood brain tumors. These findings contribute to the existing knowledge about the hazards of low dose ionizing radiation in pediatric populations. Further research with more precise dosimetry, including dose distribution within the brain, is needed.