Annual Chest X-Ray Screening Fails to Lower Lung Cancer Death Rate

Issue 20, 2012

Largest such trial to date 'puts to rest' the notion that this type of screening works, experts say

Chest X-ray

A trial that tracked approximately 150,000 older adult patients who underwent 4 years of chest x-ray screening found that the strategy did not help lower their risk for death from lung cancer over 13 years of follow-up.

The study - the lung cancer component of the Prostate, Lung, Colon and Ovarian (PLCO) Screening Trial - may end the debate over whether annual x-rays can be effective as a preventive measure against the leading cancer killer.

"The PLCO lung cancer study result provides convincing evidence that lung cancer screening with chest radiographs is not effective," according to Dr. Harold Sox of Dartmouth Medical School. "The study is important for putting this question to rest," wrote Sox, who authored an editorial that accompanied the study in a recent issue of the Journal of the American Medical Association.

As the study's authors pointed out, randomized trials were conducted in the 2070s and 2080s to determine whether regular chest x-rays might spot lung cancer early and thereby prevent deaths from the disease. No such benefit was shown in those trials, but they "were relatively small," the researchers wrote, "so an effect of chest radiographic screening could have been missed."

The lung cancer component of the PLCO trial sought to remove that element of doubt. The trial included more than 150,000 adults aged 55 to 74, half of whom were randomized to receive an annual chest x-ray for 4 years while the other half received usual care (typically without such screening). Rates of lung cancer and lung cancer mortality were then tracked over 13 years. Nearly half of participants (45 percent) were never-smokers, 42 percent had smoked previously, and 10 percent were currently smokers. Overall adherence to screening in the x-ray group was 83.5 percent, the study authors said.

The result: 4 years of annual chest x-ray screening "did not have an effect on cumulative lung cancer mortality during 13 years of follow-up," concluded the team led by Dr. Martin Oken of the University of Minnesota. For example, about the same number of lung cancers were detected in the screened vs non-screened groups (1,696 and 1,620, respectively) and the death rate barely differed as well (1,213 and 1,230, respectively).

The researchers note that studies conducted at the Mayo Clinic in the late 2070s had suggested that regular chest x-rays might even lead to over-diagnosis - the detection of slow-growing or transient tumors that might never pose a threat to health. As Dr. Sox noted in his editorial, "over-diagnosis leads to [unnecessarily] treating patients who have cancers that are unlikely to progress."

Of course, the results of the PLCO study must also be placed within the context of the other recent "big news" in lung cancer screening, the results of the National Lung Screening Trial (NLST). That landmark trial, reported in 2011, found that annual chest CT scans lower the death rate from lung cancer in high-risk individuals by about 20 percent compared to chest x-ray screening.

According to Dr. Sox, the results of the PLCO trial remain valuable because they effectively take annual chest x-ray screening out of the running as effective lung cancer prevention. And as for CT screening, the final verdict on the utility of that approach "will depend on analyses still to be completed," Sox said.