The disproportionate risk burden of CT scanning on females and younger adults in Australia: a retrospective cohort study

Objectives: To explore the interaction of computed tomography (CT) use, dose and radiation risk of Australian Medicare-funded CT scanning and the impact on cancer incidence and mortality. Methods: This retrospective cohort study used records of Medicare subsidised CT scans in Australia (2006/07 to 2011/12) and Australian CT dosimetry. The annual number, rate and adjusted likelihood of CT were determined for gender, age and examination type. Incident cancer and cancer-related mortality attributable to CT in Australia were estimated using lifetime attributable risk coefficients, dosimetry and scan numbers. Results: The number of CT scans increased by 36% from 2006/07 to 2011/12. Only patients aged 0–4 years did not present an increase in CT scanning rates. Females were 11% more likely to be scanned than males. Head, abdomen/pelvis and spine CT scans were the most likely areas scanned. Females were attributed 61% of both incident cancers and cancer-related mortality from 55% of scans performed. Patients aged 15–44 years were attributed 37% of incident cancers and 30% of cancer-related mortality from 26% of CT scans. Conclusions: CT in Australia is increasing, including in groups at higher risk from ionising radiation. This presents a complex set of risk/benefit considerations for clinicians and policy makers