1. Br J Cancer. 2016 Feb 16;114(4):388-94. doi: 10.1038/bjc.2015.415.

Relationship between paediatric CT scans and subsequent risk of leukaemia and 
brain tumours: assessment of the impact of underlying conditions.

Berrington de Gonzalez A(1), Salotti JA(2), McHugh K(3), Little MP(1), Harbron 
RW(2), Lee C(1), Ntowe E(1), Braganza MZ(1), Parker L(4), Rajaraman P(1), 
Stiller C(5), Stewart DR(1), Craft AW(2), Pearce MS(2).

Author information:
(1)Radiation Epidemiology Unit, Division of Cancer Epidemiology and Genetics, 
NCI, Bethesda, MD, USA.
(2)Institute of Health and Society, Newcastle University, Sir James Spence 
Institute, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP, UK.
(3)Great Ormond Street Hospital for Children NHS Trust, London WC1N 3JH, UK.
(4)Departments of Medicine and Paediatrics, Population Cancer Research Program, 
Dalhousie University, Halifax, Nova Scotia, Canada.
(5)New College, University of Oxford, Oxford, UK.

BACKGROUND: We previously reported evidence of a dose-response relationship 
between ionising-radiation exposure from paediatric computed tomography (CT) 
scans and the risk of leukaemia and brain tumours in a large UK cohort. 
Underlying unreported conditions could have introduced bias into these findings.
METHODS: We collected and reviewed additional clinical information from 
radiology information systems (RIS) databases, underlying cause of death and 
pathology reports. We conducted sensitivity analyses excluding participants with 
cancer-predisposing conditions or previous unreported cancers and compared the 
dose-response analyses with our original results.
RESULTS: We obtained information from the RIS and death certificates for about 
40% of the cohort (n∼180 000) and found cancer-predisposing conditions in 4 out 
of 74 leukaemia/myelodysplastic syndrome (MDS) cases and 13 out of 135 brain 
tumour cases. As these conditions were unrelated to CT exposure, exclusion of 
these participants did not alter the dose-response relationships. We found 
evidence of previous unreported cancers in 2 leukaemia/MDS cases, 7 brain tumour 
cases and 232 in non-cases. These previous cancers were related to increased 
number of CTs. Exclusion of these cancers reduced the excess relative risk per 
mGy by 15% from 0.036 to 0.033 for leukaemia/MDS (P-trend=0.02) and by 30% from 
0.023 to 0.016 (P-trend<0.0001) for brain tumours. When we included pathology 
reports we had additional clinical information for 90% of the cases. Additional 
exclusions from these reports further reduced the risk estimates, but this 
sensitivity analysis may have underestimated risks as reports were only 
available for cases.
CONCLUSIONS: Although there was evidence of some bias in our original risk 
estimates, re-analysis of the cohort with additional clinical data still showed 
an increased cancer risk after low-dose radiation exposure from CT scans in 
young patients.

DOI: 10.1038/bjc.2015.415
PMCID: PMC4815765
PMID: 26882064 [Indexed for MEDLINE]