Lung cancer screening leads to high rates of false positives
(12 June 2009: VIDYYA MEDICAL NEWS SERVICE) -- The use of computed tomography (CT) to screen people for lung cancer leads to high rates of false positives, often triggering follow-up tests and invasive procedures, researchers said at the ASCO annual meeting. Concerns about the risks and benefits of lung cancer screening with CT have been raised previously, but this is the first report to quantify the risk of obtaining false-positive results.
Dr. Jennifer M. Croswell of the NIH Office of Medical Applications of Research and her colleagues analyzed data from the Lung Screening Study (LSS), a randomized trial that compared two screening methods—CT and chest x-ray—in more than 3,000 current or former smokers between the ages of 55 and 74. The LSS, which was the feasibility study for the ongoing NCI-sponsored National Lung Screening Trial (NLST), found significantly more false positives in the CT group.
For participants in the CT group, the risk of a false positive was 21 percent after one scan and 33 percent after a second. By comparison, those in the x-ray group had a false-positive risk of 9 percent after one test and 15 percent after two. Because the LSS only included two rounds of screening, Dr. Croswell said, its findings could provide only a conservative estimate of the impact of regular lung cancer screening with CT.
Of those with false-positive results, approximately 60 percent underwent at least one follow-up imaging exam, and slightly less than 2 percent had surgery. Complication rates from these surgeries were low, but a few patients had to be hospitalized for a collapsed lung or blood in the lung (less than 1 percent), and another 1 percent were treated for infections, the researchers said. Additional imaging exams and invasive procedures were also associated with false-positive chest X-rays.
All medical interventions, including screenings, have potential risks as well as potential benefits, the researchers stressed. False positives can create psychological stress and burden the health care system, Dr. Croswell noted.
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