The National Lung Screening Trial has found that CT scans are much more sensitive than chest X-Ray for detecting lung cancer in smokers, but aren't very specific in ruling out malignancy.
Sensitivity was 94 percent and specificity 73 percent for lung cancer detection with CT compared with 74 percent and 91 percent with chest X-rays, according to research published in the May 23 issue of the New England Journal of Medicine. In the NLST first screening round, 26,309 participants underwent low-dose CT, and 26,035 participants underwent chest radiography. A total of 7,191 participants (27.3 percent) in the low-dose CT group and 2,387 (9.2 percent) in the chest X-ray group boasted a positive screening result.
After follow-up, lung cancer was diagnosed in 1.1 percent of the patients in the CT group and 0.7 percent of the X-ray group. Abstract