Lung cancer is one of the most invasive forms of cancer and is still one of the leading causes of cancer-related mortality in the United States and the rest of the world.1-3 In 2012, lung cancer will be responsible for an estimated 160,340 deaths in the United States.1-3 Five year survival rate for lung cancer is only 15.6%. The leading cause of lung cancer stems from the use of tobacco and tobacco products. The screening, by chest radiography, of patients at high risk of lung cancer remains effective but often detects only more advanced stages of lung cancer.3 Therefore, need for earlier detection and treatment is recommended, but has not been developed. The advent of low-dose helical computed tomography (CT) has altered the landscape of lung-cancer screening as studies have indicated that low-dose CT detects many tumors at earlier stages (including those located in the lungs).1,3
Aberle and colleagues of the National Lung Screening Trial Research Team (funded by the National Cancer Institute) sought to compare the use of low-dose CT as compared to chest radiography in the reduction in mortality due to lung cancer. This randomized control trial enrolled 53,454 participants at high risk for lung cancer at 33 U.S. medical centers across the US. Participants were either enrolled in 1 of the 10 in Lung Screening Study (LSS) centers or 1 of the 23 American College of Radiology Imaging Network (ACRIN) centers. Eligible participants were between ages of 55 and 74 years of age, had a history of cigarette smoking of at least 30 pack years, and, if former smokers, had quit within the previous 15 years. Participants were randomly assigned to undergo three annual screenings with either low-dose CT (26,722 participants) or single-view post-anterior chest radiography (26,732 participants). The National Lung Cancer Screening Trial (NLST) radiologist and radiological technologist, who were certified by appropriate agencies or boards, examined the images in isolation and also in comparison with available historical images. Data were collected on cases of lung cancer diagnosis and deaths from lung cancers that occurred through December 31, 2009.
The primary analysis was a comparison of lung cancer mortality between the two screening groups, according to the intention-to-screen principle. Aberle and colleges estimated that the study would have 90% power to detect a 21% decrease in mortality from lung cancer in the low-dose CT group as compared with the radiography group. There was no significant difference in the base line characteristics between the two treatment groups.
The rate of adherence to screening in both groups was greater than 90%. A positive test was identified by the investigators as any non-calcified nodule measuring at least 4 mm in any diameter and radiographic images that revealed any non-calcified nodule or mass. The rate of a positive screening test was about 24.2% with low-dose CT and 6.9% with radiography over all three rounds. A total of 96.4% of the positive screening results in the low-dose CT group and 94.5% ...