Evidencias Medicas : Cancer in children and teenagers linked with CT scanMedicina General y Familiar

09 junio, 2013

Cancer in children and teenagers linked with CT scan

English: Ct-scan of the brain with hydrocephalus Nederlands: Ct-scan van de hersenen met hydrocefalus (Photo credit: Wikipedia)

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The long-term risk of cancer is about one-fourth higher for children and adolescents exposure to computed tomography (CT) scanning, reports a study in the June 1, 2013, British Medical Journal.

Using Australian Medicare data from 1985 through 2005, the researchers identified 10.9 million children and adolescents (aged 0 to 19 years) who underwent CT scans during this time. Subsequent cancer diagnoses through 2007 were identified by linkage to national cancer data.

The incidence of cancer among children and adolescents exposed to CT scans more than 1 year before any cancer diagnosis was assessed, compared to nonexposed individuals. The lead author was John D. Mathews of University of Melbourne.

A total of 60,674 cancers were identified in the study cohort. Of these, 3,150 cancers occurred in young people with exposure to CT scanning at least 1 year before cancer diagnosis.

After adjustment for age, sex, and year of birth, overall cancer incidence was significantly higher for children and adolescents exposed to CT scanning: incidence rate ratio (IRR) 1.24. There was evidence of a dose-response effect, with IRR increasing by 0.16 per additional CT scan.

Cancer risk associated with CT scans increased with time since exposure: IRR 1.3 for 1 to 4 years, 1.25 for 5 to 9 years, 1.14 for 10 to 14 years, and 1.24 for 15 years or longer. The increase in risk was significant for many types of solid cancers as well as for leukemia, myelodysplasia, and certain other lymphoid cancers.

A total of 608 excess cancers occurred among CT-exposed young people, including 147 brain cancers, 356 other solid tumors, 48 cases of leukemia or myelodysplasia, and 57 other lymphoid cancers. Through 2007, the absolute excess incidence was 9.38 per 100,000 person-years at risk. The average effective radiation dose per CT scan was estimated at 4.5 mSv.

The increased use of CT scanning raises concerns about long-term cancer risk, particular in children. The new study demonstrates an increased incidence of cancer among children and adolescents exposed to CT scans between 1985 and 2005. The excess risk is "mostly due to irradiation," the researchers write.

Longer follow-up will be needed to determine the ultimate lifetime risk. The investigators conclude, "Future CT scans should be limited to situations where there is a definite clinical indication, with every scan optimised to provide a diagnostic CT image at the lowest possible radiation dose."

Objective To assess the cancer risk in children and adolescents following exposure to low dose ionising radiation from diagnostic computed tomography (CT) scans.

Design Population based, cohort, data linkage study in Australia.

Cohort members 10.9 million people identified from Australian Medicare records, aged 0-19 years on 1 January 1985 or born between 1 January 1985 and 31 December 2005; all exposures to CT scans funded by Medicare during 1985-2005 were identified for this cohort. Cancers diagnosed in cohort members up to 31 December 2007 were obtained through linkage to national cancer records.

Main outcome Cancer incidence rates in individuals exposed to a CT scan more than one year before any cancer diagnosis, compared with cancer incidence rates in unexposed individuals.

Results 60 674 cancers were recorded, including 3150 in 680 211 people exposed to a CT scan at least one year before any cancer diagnosis. The mean duration of follow-up after exposure was 9.5 years. Overall cancer incidence was 24% greater for exposed than for unexposed people, after accounting for age, sex, and year of birth (incidence rate ratio (IRR) 1.24 (95% confidence interval 1.20 to 1.29); P<0 .001="" 0.16="" 0.19="" 1-4="" 1.14="" 1.22="" 1.24="" 1.25="" 1.34="" 1.35="" 1.45="" 10-14="" 15="" 5-9="" a="" additional="" after="" ages="" and="" at="" by="" class="zem_slink" ct="" dose-response="" each="" exposure="" first="" for="" greater="" href="http://en.wikipedia.org/wiki/Cancer" increased="" irr="" irrs="" many="" more="" of="" or="" rel="wikipedia" relation="" respectively.="" saw="" scan.="" significantly="" since="" target="_blank" the="" title="Cancer" to="" trend="" types="" was="" we="" were="" years="" younger="">solid cancer

(digestive organs, melanoma, soft tissue, female genital, urinary tract, brain, and thyroid); leukaemia, myelodysplasia, and some other lymphoid cancers. There was an excess of 608 cancers in people exposed to CT scans (147 brain, 356 other solid, 48 leukaemia or myelodysplasia, and 57 other lymphoid). The absolute excess incidence rate for all cancers combined was 9.38 per 100 000 person years at risk, as of 31 December 2007. The average effective radiation dose per scan was estimated as 4.5 mSv.

Conclusions The increased incidence of cancer after CT scan exposure in this cohort was mostly due to irradiation. Because the cancer excess was still continuing at the end of follow-up, the eventual lifetime risk from CT scans cannot yet be determined. Radiation doses from contemporary CT scans are likely to be lower than those in 1985-2005, but some increase in cancer risk is still likely from current scans. Future CT scans should be limited to situations where there is a definite clinical indication, with every scan optimised to provide a diagnostic CT image at the lowest possible radiation dose.