Lung Cancer Screening Often Yields False Positives
Last Updated: 2010-04-19 17:00:29 -0400 (Reuters Health)
By Amy Norton
Researchers say the findings point to a significant downside of using the tests -- chest X-rays or spiral CT scans -- to try to detect lung cancer early.
In recent years, CT scans in particular have been promoted by some hospitals and advocacy groups for lung cancer screening, even though studies have not yet shown whether such screening saves lives.
"The most important thing right now is to try to figure out if this lowers death rates," Dr. Jennifer M. Croswell, the lead researcher on the new study, told Reuters Health.
The current findings, she said, add "pieces to the puzzle" by estimating the likelihood of false-positive results with repeated screening tests over time.
Dr. Croswell and her colleagues at the National Institutes of Health in
Overall, the chances of having a false-positive result were 21% after one CT scan, and 33% after two.
With chest X-rays, there was a 9% chance of a false-positive after one test, and a 15% chance after two, according to the April 20th online report in the Annals of Internal Medicine.
Seven percent of subjects with false-positive CT results had invasive follow-up procedures; most commonly, a bronchoscopy. Eight patients, however, had surgery for what turned out to be benign conditions.
Four percent of subjects with false-positive chest X-rays went on to have invasive procedures.
The findings come from the pilot phase of an ongoing NIH clinical trial looking at whether CT or chest X-ray screening cuts death rates among people at increased risk of lung cancer. The trial, which began in 2002, ultimately enrolled more than 53,000 current and former smokers, and the results could become available in the next couple years, Dr. Croswell said.
Despite the current lack of proof that screening prevents deaths, certain hospitals and advocacy groups have been promoting CT scans, which cost anywhere from $300 to $1,000 per test, for lung cancer screening.
"Most professional medical societies do not recommend (lung cancer screening) right now," Dr. Croswell said, "and the reason is because we don't know if it works."
Ann Intern Med 2010.
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