Radiation Doses From Pediatric CT Scans In Great Britain (1978-2008): A Survey Of Individual Exposures And A Risk Assessment Of Potential Subsequent Cancers

Neige JOURNY, National Cancer Institute, National Institutes of Health, United States
LEE C. 1 , PEARCE M. 2 , HARBRON R. 2 , LITTLE M. 1 , MCHUGH K. 3 , BERRINGTON DE GONZALEZ A. 1

1 Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute (NCI), National Institutes of Health, Bethesda, US
2 Institute of Health & Society, Newcastle University, Newcastle-upon-Tyne, UK
3 Great Ormond Street Hospital for Children, London, UK

Background: Despite the great medical benefits, there are concerns that use of computed tomography (CT) can increase risk of cancer, especially in children. This study aims to assess individual exposures in children or young adults scanned in Great Britain and projecting the potentially radiation-induced cancers from the 1980’s to the current time.

Methods: Individual scan parameters were collected for 1,073 CT scans performed in 1978-2008 in 36 hospitals in patients before 20 years of age. Organ doses were estimated using experimentally validated dose conversion coefficients. Lifetime cancer risks were projected using dose-response models derived from data for the Japanese atomic bomb survivors and for patients exposed to X-rays (RadRAT risk assessment tool), and using national cancer and mortality statistics. Total numbers of cancer were projected up to 2014 using data of the Diagnostic Imaging Dataset (Office for National Statistics, England) and trends in CT use reported in a previous survey in the UK.

Results: In 2000-2008, organ doses per exam and subsequent lifetime cancer risks were 50-70% lower than in 1978-1989. In 2000-2008, the projected lifetime risks varied from 3 to 9 per 10,000 head scans and 9 to 45 per 10,000 body scans according to the age at scan. We calculated that 57 cancers (90% uncertainty interval: 34-97) might be induced over the patients’ lifetime by the 103,000 scans performed in England in 2014 in individuals under 20 years of age.

Conclusion: There have been reductions in dose per CT exam in pediatric CT since 1995, but a more widespread use of CT has increased collective exposure. This study projected numbers of possibly radiation-induced cancers, resulting both from reduced individual doses and an increased frequency of use.  

Funding sources: NCI intramural research program, UK Department of Health, Cancer Research UK