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Clinical Trial Results

Summaries of Newsworthy Clinical Trial Results
  • Posted: 12/02/2011

Annual Screening with Chest X-Ray Does Not Reduce Lung Cancer Deaths

Adapted from the NCI Cancer Bulletin.

Annual screening for lung cancer using a standard chest x-ray does not reduce the risk of dying from lung cancer when compared with no annual screening, according to findings from the NCI-led Prostate, Lung, Colorectal, and Ovarian (PLCO) screening trial. The results from a median of nearly 12 years of follow-up were published online October 26, 2011 in JAMA.

Participants in the trial who were randomly assigned to receive an annual chest x-ray for 4 consecutive years had nearly the same mortality rate from lung cancer as participants randomly assigned to receive usual care—that is, care they would typically receive in their own community.

PLCO is one of the largest cancer screening trials ever conducted. The trial involved nearly 155,000 participants between the ages of 55 and 74. Participants were screened for four different cancers at one of 10 designated centers between November 1993 and July 2001.

Unlike participants in the National Lung Screening Trial (NLST)—the results of which were initially presented late last year—PLCO participants were not at increased risk of cancer. Only 10 percent of participants were current smokers and 42 percent were former smokers. Among participants in the screening arm of the PLCO trial, 91.3 percent were screened at least once and 83.5 percent had all four chest x-rays. Only 11 percent of patients in the usual care, or control, arm of the trial had a chest x-ray to screen for lung cancer during the 4-year intervention period.

In NLST, screening with low-dose helical computed tomography (CT) was compared to chest x-ray in patients who were at increased risk of lung cancer, primarily because of their smoking history. The results showed a 20 percent reduction in lung cancer mortality associated with CT. When PLCO researchers looked at the subset of about 30,000 patients in their trial who would have been candidates for NLST based on their smoking history, there was a suggestion of a slight reduction in lung cancer mortality risk associated with screening at 6 and 13 years of follow-up. This finding, however, did not achieve statistical significance.

Only 18 percent of the lung cancers diagnosed in the screening arm of PLCO were diagnosed during the trial's intervention period. But, according to Christine Berg, M.D., of NCI's Division of Cancer Prevention, the principal investigator of the PLCO and NLST, a longer screening period most likely would not have made a difference given the lack of a mortality reduction in higher-risk participants.

Results from the trial "are as definitive as most studies get," Dr. Berg continued. "They really indicate that lung cancer screening with chest x-ray is of no benefit for reducing lung cancer mortality, regardless of an individual's risk profile."

Research groups are still analyzing the NLST results, Dr. Berg added, including the implications of the high false-positive rate associated with CT screening in that trial.