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Radiation risk of screening with low dose CT
  1. R L Karadi
  1. Department of Respiratory Medicine, Hope Hospital, Salford, UK; klranga{at}

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I read with interest the article by MacRedmond et al1 on screening for lung cancer using low dose CT scanning and the related editorial by Gleeson2 which provides a comprehensive summary of the benefits and potential pitfalls of such a screening. However, I noticed that, in both articles, the important issue of the potential radiation risks associated with low dose CT screening for lung cancer has not been addressed.

Previously published reports have suggested radiation risks even with a low dose CT scan as part of a regular screening programme3 and also of a possible synergistic interaction between the risk from smoking and radiation exposure.4–,7 Brenner3 estimates that, if 50% of all current and former smokers in the US population aged 50–75 years received annual CT screening, the estimated number of lung cancers associated with radiation from screening would be 1.8% (95% credibility interval 0.5% to 5.5%) more than the otherwise expected number. Considering an upper limit of a 5.5% increase in lung cancer risk attributable to annual CT related radiation exposure, he feels that a mortality benefit of considerably more than 5% would be necessary to outweigh the potential risks of radiation. This estimation was derived from cancer incidence data for atomic bomb survivors.7

Several other reports4–6,8 have suggested a link between radiation exposure and lung cancer. Potential radiation risks associated with multiple CT scans should therefore be considered as one of the limiting factors for such screening.



  • Competing interests: none declared.

  • Dr MacRedmond was asked to comment but no reply who received by the time this issue of Thorax went to press.