New Criteria Could Reduce False Positives in Lung Screening

A retrospective study led by National Cancer Institute researchers found that new criteria for classifying lung nodules discovered through low-dose computed tomography (LDCT) may substantially reduce the false-positive result rate in lung cancer screening.

A team led by Paul Pinsky, PhD, MPH, the acting chief of the early detection research group in the division of cancer prevention at the National Cancer Institute, applied new Lung-RADS criteria to patients who had previously been screened with LDCT as part of the National Lung Screening Trial (NLST).
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Note: Lung-RADS is the classification system for LDCT cancer screening that was recently released by the American College of Radiology.

In their study, Pinsky and colleagues randomly assigned participants to the LDCT group of the NLST. These patients were between the ages of 55 and 74-years-old, had at least a 30-pack-a-year history of smoking, were current smokers, or had quit within the past 15 years.

Among the 26,722 LDCT group participants, 26,455 received a baseline screen and 48,671 screenings were done after baseline. At baseline, the false-positive result rate for Lung-RADS was 12.8%, vs. 26.6% for the NLST. After baseline, the false-positive result rate was 5.3% for Lung-RADS compared to 21.8% for the NLST. Baseline sensitivity was 84.9% for Lung-RADS compared to 93.5% for the NLST, and sensitivity after baseline was 78.6% for Lung-RADS vs. 93.8% for the NLST.

The findings show that, using Lung-RADS, the false-positive rate with low-dose CT lung cancer screening “would be expected to be substantially lower than that seen in the NLST,” says Pinsky.

“This is a positive development,” he says, to the extent that false-positive results cause negative consequences for patients—anxiety, possible complications of invasive follow-up procedures, extra radiation from follow-up CTs, potential out-of-pocket costs and inconvenience—as well as a strain on healthcare resources and physicians’ time.

When regular screening becomes disseminated in the population, “most low-dose CT screens will be post-baseline screens, where the reduction in the false-positive rate was greatest,” he says, noting that the observed 5% false-positive rate with Lung-RADS in these screens “is quite acceptable in a screening setting.”

While the effect of the corresponding decrease in sensitivity on the lung-cancer mortality reduction of screening would be expected to be small, “the actual effect is not known currently,” says Pinsky. While the use of Lung-RADS may reduce some of the harms associated with LDCT, “it is still important at this point in time to restrict screening to those groups covered by the USPSTF’s recommendations,” he says, which encompasses individuals between the ages of 55 and 80-years-old who either currently smoke or have quit smoking within 15 years.

—Mark McGraw

Reference:

Pinsky P, Gierada D, et al. Performance of Lung-RADS in the National Lung Screening Trial: A Retrospective Assessment. Ann Intern Med. 2015.