A computed tomography (CT) scan can uncover tumours not yet visible on an X-ray. CT scanning is now being actively evaluated as a screening tool for lung cancer in high risk patients, and it is showing promising results. The USA-based National Cancer Institute is currently completing a randomized trial comparing CT scans with chest radiographs. Several single-institution trials are ongoing around the world.
The International Early Lung Cancer Action Project published the results of CT screening on over 31,000 high-risk patients in late 2006 in the New England Journal of Medicine.[27] In this study 85% of the 484 detected lung cancers were stage I and thus highly treatable. Mathematically these stage I patients would have an expected 10-year survival of 88%. However, there was no randomization of patients (all received CT scans and there was no comparison group receiving only x-rays) and the patients were not actually followed out to 10 years post detection (the median followup was 40 months).
In contrast, a March 2007 study in JAMA found no benefit. 3,200 current or former smokers were screened for 4 years and offered 3 or 4 CT scans. Lung cancer diagnoses were 3 times as high, and surgeries were 10 times as high, as predicted by a model, but there were no significant differences between observed and expected numbers of advanced cancers or deaths.
Randomized controlled studies are underway in this area to see if decreased long-term mortality can be directly observed from CT screening.
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