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

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


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.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Brain Neoplasms / diagnostic imaging
  • Brain Neoplasms / epidemiology*
  • Brain Neoplasms / etiology
  • Child
  • Cohort Studies
  • Female
  • Humans
  • Leukemia / diagnostic imaging
  • Leukemia / epidemiology*
  • Leukemia / etiology
  • Male
  • Neoplasms, Radiation-Induced / diagnostic imaging
  • Neoplasms, Radiation-Induced / epidemiology*
  • Neoplasms, Radiation-Induced / etiology
  • Retrospective Studies
  • Tomography, X-Ray Computed / adverse effects
  • Tomography, X-Ray Computed / statistics & numerical data*
  • Young Adult