Methods
Patients and study design
In our observational retrospective cohort study, we included patients without previous malignant disease who were first examined with CT between 1985 and 2002 when they were younger than 22 years of age. Patients were scanned at hospitals within 81 National Health Service (NHS) regional services in Great Britain (England, Wales, and Scotland). We assembled the cohort with historical data from electronic radiology information systems (RIS) from the participating hospitals or, for a small number of patients in five hospitals, from paper or film records. Retrieved data included date of birth, details of the CT examinations, sex, post code, and body parts scanned. We used the patient's identifiers to identify patients having scans in more than one hospital.
This study was approved by the Newcastle and North Tyneside Local Research Ethics Committee (Newcastle upon Tyne, UK) and by the UK National Information Governance Board, exempting the study from requiring individual patient's consent.