69 Background: In general, clinical practice guidelines do not recommend the use of diagnostic imaging in long-term surveillance of cancer survivors. Although warranted diagnostic imaging has clinical benefits, the overuse of imaging in cancer survivors may lead to false-positive results, more invasive tests, economic burden and unnecessary radiation exposure. The objective of this study was to determine rates of diagnostic imaging in long-term young adult cancer survivors (YAS) compared to cancer-free controls in Ontario, Canada. Methods: We conducted a population-based retrospective study. Young adults aged 20 to 44 diagnosed with an invasive malignancy between 1992 and 1999 who lived at least 5 years without recurrent disease were identified in the Ontario Cancer Registry. YAS were matched 1:5 to randomly selected cancer-free controls on calendar year of birth, sex, and place of residence. The rate at which YAS received plain radiography, CT, ultrasound and nuclear medicine studies was compared to rates received by controls using Poisson regression. Results: 20,911 survivors and 104,524 controls met our inclusion criteria. YAS received all types of diagnostic imaging at significantly higher rates than controls in the 10 year period after 5-year recurrence-free survival. YAS received CT scanning at a rate 3.6-fold higher than controls (95% confidence interval [CI]: 3.37, 3.62). In contract, the difference in rates of ultrasound between the two groups was more modest (rate ratio [RR] = 1.40, 95% CI: 1.38, 1.43). YAS also received plain radiography (RR =1.66, 95% CI: 1.64, 1.69) and nuclear studies (RR=1.97, 95% CI: 1.89, 2.04) at significantly higher rates than controls, resulting in a 4.6-fold adjusted higher diagnostic radiation dose than controls. Conclusions: Survivors received significantly higher rates of all diagnostic studies after 5-year survival compared to their age-matched cancer-free counterparts. Hazards associated with overuse of imaging such as radiation exposure and heightened anxiety about test results need to be considered. Both patients and providers should be educated about the role of diagnostic imaging in long-term surveillance including the utility of studies without radiation, such as ultrasound.
Patterns of diagnostic imaging and associated radiation exposure among long-term survivors of young adult cancer: a population-based cohort study
