Estimating risk associated with radiation exposure during follow-up after endovascular aortic repair (EVAR)

Abstract

Late rupture incidence following endovascular repair (EVAR) of abdominal aortic aneurysm does not appear to decrease with time, mandating life-long surveillance. Popular regimes based on computed tomography (CT) originated in early registry and randomised trial protocols and are not evidence-based. We evaluated the radiation burden (and implications) associated with "conventional" CT surveillance and explored alternative surveillance paradigms. An EVAR program comprising planning CT, EVAR and surveillance CT at 1, 3, 6 and 12 months and yearly thereafter, equates to a total effective radiation dose of around 145-205 mSv over five years. A 70-year-old exposed to 145 mSv has a lifetime attributable cancer risk of 0.42% (i.e., odds of 1 in 240). Similarly, for a total dose of 204 mSv, the risk would be 0.60% (1 in 170). The corresponding data for a 50-year-old would be 0.73% (1 in 140) and 1.03% (1 in 100), respectively. In high throughput units this could mean one cancer per year attributable to the EVAR programme. Of particular concern is the cumulative dose in those most sensitive to it; younger patients, smokers and women. Repeat exposure within short exposure intervals is particularly burdensome (e.g., planning CT followed by EVAR one week later and first surveillance CT at one month). Three alternatives reduce radiation exposure; reduction of the effective dose associated with each CT scan, reduction in the number of CT scans requested (or better temporal spacing of them) or replacement of CT with alternative modes of imaging/assessment.