Objective: Prior analyses of X-ray exposures in lung cancer screening with CT considered the basic acquisition technique in single-detector scanners and the effects of a lifetime screening regimen, whereas the potential benefit in terms of lives saved was not addressed.
Materials and methods: We determined the total-body effective dose of different acquisition techniques for one single-detector and one MDCT scanner and made projections about the cumulative radiation exposure to smokers undergoing four annual CT examinations on the same scanners in the Italung-CT Trial. Combining these data with estimates of radiation-induced fatal cancer and of the benefit of screening, we calculated the risk-benefit ratio for participants in the trial, ex-smokers, and never-smokers.
Results: The cumulative effective doses per 1,000 subjects were 3.3 Sv using an MDCT scanner and 5.8 or 7.1 Sv using a single-detector scanner. Potential fatal cancers associated with radiation exposure were 0.11 per 1,000 subjects for MDCT scanners and 0.20 or 0.24 for single-detector scanners, which is about 10-100 times lower than the number of expected lives saved by screening assuming a 20-30% lung cancer-specific mortality reduction in current smokers. They were, however, of similar magnitude to the lives saved by screening in never-smokers and former smokers assuming a 10% efficacy of screening.
Conclusion: MDCT is associated with lower radiation doses than single-detector CT technology. The risk of radiation dose in the Italung-CT Trial is compensated for by the expected benefit. CT screening for lung cancer should not be offered to never-smokers, whereas its recommendation in former smokers is debatable.