Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study

Abstract

SummaryBackgroundAlthough CT scans are very useful clinically, potential cancer risks exist from associated ionising radiation, in particular for children who are more radiosensitive than adults. We aimed to assess the excess risk of leukaemia and brain tumours after CT scans in a cohort of children and young adults.MethodsIn our retrospective cohort study, we included patients without previous cancer diagnoses who were first examined with CT in National Health Service (NHS) centres in England, Wales, or Scotland (Great Britain) between 1985 and 2002, when they were younger than 22 years of age. We obtained data for cancer incidence, mortality, and loss to follow-up from the NHS Central Registry from Jan 1, 1985, to Dec 31, 2008. We estimated absorbed brain and red bone marrow doses per CT scan in mGy and assessed excess incidence of leukaemia and brain tumours cancer with Poisson relative risk models. To avoid inclusion of CT scans related to cancer diagnosis, follow-up for leukaemia began 2 years after the first CT and for brain tumours 5 years after the first CT.FindingsDuring follow-up, 74 of 178 604 patients were diagnosed with leukaemia and 135 of 176 587 patients were diagnosed with brain tumours. We noted a positive association between radiation dose from CT scans and leukaemia (excess relative risk [ERR] per mGy 0·036, 95% CI 0·005–0·120; p=0·0097) and brain tumours (0·023, 0·010–0·049; p<0·0001). Compared with patients who received a dose of less than 5 mGy, the relative risk of leukaemia for patients who received a cumulative dose of at least 30 mGy (mean dose 51·13 mGy) was 3·18 (95% CI 1·46–6·94) and the relative risk of brain cancer for patients who received a cumulative dose of 50–74 mGy (mean dose 60·42 mGy) was 2·82 (1·33–6·03).InterpretationUse of CT scans in children to deliver cumulative doses of about 50 mGy might almost triple the risk of leukaemia and doses of about 60 mGy might triple the risk of brain cancer. Because these cancers are relatively rare, the cumulative absolute risks are small: in the 10 years after the first scan for patients younger than 10 years, one excess case of leukaemia and one excess case of brain tumour per 10 000 head CT scans is estimated to occur. Nevertheless, although clinical benefits should outweigh the small absolute risks, radiation doses from CT scans ought to be kept as low as possible and alternative procedures, which do not involve ionising radiation, should be considered if appropriate.FundingUS National Cancer Institute and UK Department of Health.

CT exposure in adult and paediatric patients: a review of the mechanisms of damage, relative dose and consequent possible risks

“…Two relevant epidemiological studies on low-dose cancer risk have recently been published by Pearce in the Lancet and Mathews et al in the BMJ and regarded British and Australian young subjects affected by leukaemia and other solid cancers [34,35]. Mathews et al compared the cancer incidence rates in individuals exposed to a CT scan more than 1 year before any cancer diagnosis with the incidence rates in unexposed individuals.…”

Variations of the soft tissue thicknesses external to the ribs in Pectus Excavatum patients

“…CT scan produces larger amounts of radiation compared with other imaging modalities. Without a combination of sufficient technical understanding and appropriate application, this technology can increase the risk and the probability of cancer, hair loss and dermatitis with cumulative doses (radiation) [10,[20][21][22][23][24]. Most PE patients seek healthcare advice during late childhood and adolescence when they are most affected by social and psychological commitments [2,3].…”

Both sides now: diagnostic imaging medical physics in two hemispheres

“…There is nothing more undermining to good radiation safety practice than the belief or suspicion "that it might be good for us after all." Whilst there is debate about the methodological detail, recent papers using a Big Data approach show for the first time a causal dose response relationship between radiation received from CT scans by children and cancer incidence [4,5]. The findings of 50-60 mGy tripling leukaemia and brain cancer risk, and 4.5 mSv resulting in a 24% increase in cancer and leukaemia incidence brings known deleterious effects into diagnostic imaging territory.…”