Yearly CT scans of middle-aged and older smokers — and former smokers — can reduce the risk of death from lung cancer by 20 percent, according to an eight-year, landmark study funded by the federal government. Health experts say the study results represent a historic leap forward in cancer detection that could save thousands of lives each year, although at considerable cost.

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CT scans of smokers and former smokers reduced deaths from lung cancer by 20 percent. — SuperStock

"We have finally demonstrated that most lung cancers can be detected early," says Christine Berg, M.D., of the National Cancer Institute, the lead author of the study.

Lung cancer kills far more Americans than any other type of cancer. It strikes more than 220,000 people each year and kills about 160,000 of those, more than colon, breast and prostate cancers combined.

Previously, doctors only ordered computed tomography scans (CTs) or x-rays for smokers who complained of symptoms, such as coughing up blood. Health experts say this study is likely to lead to a push for widespread screening using CT scans on millions of older smokers. "It's a game-changing trial for lung cancer screening," says Harold Sox, M.D., a professor emeritus at Dartmouth Medical School who wrote an editorial commenting on the study, released online Wednesday in the New England Journal of Medicine.

But even some experts who hailed the study's results question whether the research will lead to costly, unnecessary screening and procedures on men and women who are not really at high risk. Biopsies and lung surgery on older people can be dangerous, even deadly.

For 30 years, researchers and cancer doctors watched in frustration as study after study designed to screen for lung cancer failed. Even when x-rays could find tumors in lungs, they didn't save lives because it was too late. As CT scan technology improved, Berg and other researchers thought the scans might be able to catch lung tumors at an early enough stage to improve survival.

They tested that theory in this National Lung Screening Trial with more than 53,000 people ages 55 to 74 who had smoked at least one pack a day for 30 years or two packs a day for 15 years. They also included heavy smokers who had quit smoking within the last 15 years. Older former smokers who quit more than 15 years ago were not included in the study, because over the years their risk of lung cancer drops considerably.

Next page: Dramatic CT scans results stop trial early »