Candidate for the Lee B. Lusted Student Prize Competition
Purpose: Increasing concerns about radiation-induced cancer risks from computed tomography (CT) have prompted consideration of alternate imaging modalities for suspected appendicitis. We compared life expectancy losses attributable to three imaging strategies, incorporating mortality risks from both acute appendicitis and radiation-induced cancers.
Methods: We developed a decision-analytic model to compare life expectancy losses attributable to the use of abdominopelvic CT alone, combined ultrasound and CT (e.g. ultrasound followed by CT in cases where results were negative or indeterminate), and abdominopelvic magnetic resonance imaging (MRI) for the diagnosis of appendicitis. We designated, as our base case, 20-year-old men with suspected acute appendicitis. Disease prevalence, test performance characteristics, and mortality from appendicitis and appendectomy were elicited from the literature. CT effective dose levels were based upon institutional data. Life expectancy losses due to radiation-induced cancers were projected using an organ-specific model of radiation-induced cancer risks that was developed using the Biological Effects of Ionizing Radiation (BEIR VII) report. One-way and two-way deterministic sensitivity analyses were performed to evaluate effects of parameter variability upon model results.
Results: In the base-case analysis, the combined ultrasound-CT strategy resulted in the least average life expectancy loss (8.30 days in total, 1.10 days due to radiation-induced cancers). Use of CT alone resulted in a minimally greater life expectancy loss of 9.92 days (1.70 days due to radiation-induced cancers), and use of MRI alone resulted in a life expectancy loss of 10.94 days (MRI does not confer ionizing radiation). In sensitivity analysis, we found that favorability of the combined ultrasound-CT strategy over CT alone was driven primarily by test performance characteristics and not radiation-induced cancer risks. Substitution of low-dose CT for standard CT did not change strategy rankings. MRI became the preferred strategy only if life expectancy losses attributable to radiation-induced cancers from a CT scan exceeded 5.76 days, which would be very unlikely given current dosimetry practices.
Conclusions: We found that a combined ultrasound and CT approach will optimize life expectancy relative to CT or MRI alone; however, this result is driven by differences in test performance characteristics, and not radiation-induced cancer risks.
See more of: The 34th Annual Meeting of the Society for Medical Decision Making