In a European cohort study (EPI-CT) reported in The Lancet Oncology, Hauptmann et al found an increased risk of brain cancer with increasing brain radiation dose among children and young adults who had undergone computed tomography (CT) scans.
Study Details
The study used pooled data from nine European countries on individuals with no history of cancer who had at least one CT examination before age 22 years between 1977 and 2014 and were alive and cancer-free 5 years after their first CT examination. Excess relative risks (ERRs) of brain cancer per 100 mGy of cumulative brain dose were calculated using linear dose-response modeling. The outcome of interest was first reported diagnosis of brain cancer after an exclusion period of 5 years from the first CT examination.
Key Findings
Analysis was performed in a total of 658,752 eligible individuals; of these, 481,532 (73%) had received at least one head or neck CT examination.
Median follow-up—beginning after the 5-year exclusion period—was 5.6 years (interquartile range = 2.4–10.1 years). A total of 165 brain cancers were identified, including 121 gliomas (73%).
A significant positive association was observed between the cumulative number of head or neck CT examinations and risk for all brain cancers (P < .0001) and for gliomas alone (P = .0002).
The mean cumulative brain radiation dose was 47.4 mGy (standard deviation [SD] = 60.9 mGy) among all individuals and 76.0 mGy (SD = 100.1 mGy) among those who developed brain cancer. A significant linear dose-response relationship was observed for all brain cancers (ERR per 100 mGy = 1.27, 95% confidence interval [CI] = 0.51–2.69) and for gliomas alone (ERR per 100 mGy = 1.11, 95% CI = 0.36–2.59).
Compared with cumulative doses < 5 mGy, relative risks for all brain cancers were 2.1 (95% CI = 1.1–3.8) for doses ranging from 41 to 47 mGy and 5.0 (95% CI = 2.5–9.7) for doses ≥ 150 mGy.
Similar findings were made in analyses in which follow-up after first CT examination was started at 6 to 10 years after the exclusion period. Findings were also similar when participants with potential previously unreported cancers were excluded by limiting analysis to more recent calendar periods of case ascertainment—ie, to avoid inclusion of those with malignancies that were not reported due to incomplete cancer registration.
The investigators concluded, “The observed significant dose-response relationship between CT-related radiation exposure and brain cancer in this large, multicenter study with individual dose evaluation emphasizes careful justification of pediatric CTs and use of doses as low as reasonably possible.”
Michael Hauptmann, PhD, of the Institute of Biostatistics and Registry Research, Brandenburg Medical School, Germany, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was funded by EU FP7, Belgian Cancer Registry, La Ligue contre le Cancer, L’Institut National du Cancer, and others. For full disclosures of the study authors, visit thelancet.com.
