New lung cancer screening guidelines recommend annual CT scans but only for current or former heavy smokers aged 55 to 74.
The risks of screening younger or older smokers or nonsmokers outweigh any benefits.
That's according to guidelines issued Sunday by the American College of Chest Physicians, the American Society of Clinical Oncology and the National Comprehensive Cancer Network.
The guidelines are for adults in that age range with a history of smoking a pack of cigarettes daily for 30 years, or two packs daily for 15 years.
CT scans are special X-rays that can detect lung cancer early, but can also have false-positive results.
It's estimated that 8 million Americans would be eligible for screening under the guidelines.