Screening current or former smokers with the imaging technique of computed tomography may increase the rate of diagnosis and treatment of lung cancer, but may not necessarily reduce the risk of advanced lung cancer or death from lung cancer.

Lung cancer accounts for 25 percent of cancer deaths and 6 percent of all deaths in the United States. Screening with chest x-rays is not effective in reducing the risk of advanced lung cancer or death. There is hope that lung cancer screening with computed tomography ( CT ) will be more effective at reducing deaths from lung cancer because it is more sensitive for the detection of very small nodules.

Peter B. Bach, of Memorial Sloan-Kettering Cancer Center, New York, and colleagues examined the effect of CT screening on individuals by comparing the frequency of lung cancer detection, resection, advanced lung cancer cases, and deaths from lung cancer with what would have occurred in the absence of screening. The study ( a combination of three studies ) included 3,246 asymptomatic current or former smokers screened for lung cancer beginning in 1998 either at one of two academic medical centers in the United States or an academic medical center in Italy with follow-up for a median of 3.9 years. Participants received annual CT scans with comprehensive evaluation and treatment of detected nodules.

The researchers found that individuals screened with CT were three times more likely to be diagnosed with lung cancer ( 144 diagnosed cases vs. 44.5 expected cases ), and 10 times more likely to undergo a lung cancer surgery ( 109 individuals with lung surgery vs. 10.9 expected cases ). Computed tomography screening did not appear to reduce the risk of advanced lung cancer diagnoses or deaths due to lung cancer.

" Our finding of a 10-fold increase in lung cancer surgeries resulting from screening underscores one of the potential public health consequences of CT screening. If the majority of excess early cancers found through screening are unlikely to progress rapidly to a point where they cause clinically significant disease or death, then the thoracic surgeries performed to remove them may be insufficiently beneficial to justify the resulting morbidities," the authors write.

" Our findings that CT screening is not associated with a reduction in the chance that a person will develop advanced lung cancer or die from lung cancer are important negative results that should influence how screening is viewed up until that time when more rigorous data are available from randomized trials."

" These findings, because they are thematically consistent with the findings of several randomized studies of lung cancer screening with chest X-ray, should raise doubts about the premise underpinning CT screening for lung cancer, and also raise concerns about its potential harms if pursued on a wide scale," the researchers write.

Source: Journal of American Medical Association, 2007

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