What evidence supports screening smokers for lung cancer to reduce mortality?
In patients with a significant (greater than 50 pack-year) history of smoking, yearly screening for lung cancer using low-dose computed tomography (CT) will extend their lives. A significant proportion of screened patients will have a false-positive finding or a finding not related to lung cancer. As with many screening programs, there is likely a societal benefit to overall decreased mortality, although the likelihood of benefit to any individual will be small. (Level of Evidence = 1a)
This systematic review focused on the effectiveness of CT screening of smokers for lung cancer, hoping that early detection would decrease lung cancer–related mortality as well as all-cause mortality. The investigators searched several databases, including the Cochrane Library, and reference lists from identified articles to find four English-language studies. These studies enrolled current or former smokers 50 years or older and compared annual CT screening with chest radiography or usual care. Only one of the four trials was deemed to be of good quality, and the conclusions from this review stem from this single study. It was also the largest study by a factor of 10. In this study of more than 53,000 patients screened yearly for three years and then followed for an additional 3.5 years, there was a 20% decrease in lung cancer–related mortality and a 6.7% decrease in mortality by any cause (95% confidence interval, 1% to 27%). The other smaller studies did not find a benefit to screening. False-positive results were common. CT screening also frequently identified other clinically significant abnormalities that were not lung cancer in 7.5% of patients. These “screenomas” probably resulted in further testing, and the benefits or harms were not reported. The rate of overdiagnosis could not be calculated.
Study design: Systematic review
Funding source: Government
Reference: HumphreyLLDeffebachMPappasMet alScreening for lung cancer with low-dose computed tomography: a systematic review to update the U.S. Preventive Services Task Force recommendation. Ann Intern Med.2013; 159( 6): 411– 420.