Computed tomography screening for lung cancer: review of screening principles and update on current status

Screening for lung cancer with low-dose computed tomography (CT) is controversial. In favor of screening, lung cancer is the leading cause of cancer death in the United States, and those at greatest risk are identified readily on the basis of age and smoking history. In addition, it is well established that CT is far more sensitive than chest radiography in detecting lung cancer when it is small and asymptomatic. Furthermore, very high rates of survival were reported recently for screen-detected lung cancers in a large, multinational, single-arm observational study. However, a reduction in lung cancer mortality has not been demonstrated to date, and a recent longitudinal study with a simulated control group suggested little or no mortality reduction. In addition, there are important harms from CT screening, including false-positive test results and overdiagnosis. Furthermore, healthcare resources are finite. Therefore, even if the benefits do outweigh the harms, the cost-effectiveness of CT screening for lung cancer still will need to be considered in the context of competing healthcare alternatives. The objectives of this article were 3-fold: 1) to review the basic principles of screening and study designs related to cancer screening, 2) to summarize the results of the observational and analytical studies of CT screening that have been reported to date, and 3) to describe the design of the 2 ongoing, randomized controlled trials of CT screening and what may be learned from these studies in the near future.