CHICAGO (AP) ― New lung cancer screening guidelines from three medical groups recommend annual scans but only for an older group of current or former heavy smokers.

The advice applies only to those aged 55 to 74. The risks of screening younger or older smokers or nonsmokers outweigh any benefits, according to the guidelines.

About 8 million Americans would be eligible for screening under the new criteria, and if all of them got the scans, about 4,000 lung cancer deaths per year could be prevented, said Dr. Peter Bach of Memorial Sloan-Kettering Cancer Center in New York.

He chaired the expert panel that wrote the new guidelines for the American College of Chest Physicians, the American Society of Clinical Oncology and the National Comprehensive Cancer Network.

The recommended screening involves low-dose CT scans, which are a special kind of X-ray that can detect lung cancer early, but also can have false-positive results.

Regular chest X-rays can also detect lung cancer but they provide less detailed images than CT scans, can also have false-positive results and have not been recommended as a screening tool because they have not been shown to save lives.

The guidelines were published online Sunday in the Journal of the American Medical Association.

An estimated 226,000 Americans will be diagnosed with lung cancer this year. It is the leading cause of cancer deaths for U.S. men and women. An estimated 160,000 lung cancer deaths nationwide will occur this year. That number has declined in recent years, partly because of better detection and fewer people smoking.

Widespread screening will likely lead to some deaths because abnormal results are typically followed by biopsies and other invasive tests that sometimes have deadly complications. Still, the three groups say those deaths would be far outnumbered by people saved from lung cancer deaths by screening.

The recommendations go slightly further than preliminary guidance issued last year by the American Cancer Society and targeting current or heavy smokers in the same age range. That guidance said eligible adults “may consider” CT screening but should discuss risks and benefits with their physicians.

The new guidelines say screening with low-dose CT scans should be offered, but only in academic medical centers and other sites with specialized radiologists and surgeons on staff.

The guidance is based on a review of evidence including a large National Cancer Institute study involving more than 53,000 people with a history of smoking at least one cigarette pack daily for 30 years or two packs for 15 years. The guidelines recommend screening only for people who have smoked that much.

The study is considered the strongest evidence favoring CT screening and also was the basis for the cancer society’s guidance and recent similar guidelines from the American Lung Association.

The U.S. Preventive Services Task Force, a government-appointed panel that issues public health guidance, is evaluating that study as it prepares to update its 2004 stance on lung cancer screening. The task force said then that there was insufficient evidence to recommend lung cancer screening with CT scans, X-rays or sputum tests.

Dr. Otis Brawley, chief medical officer at the American Cancer Society, took part in the new review and said his group likely will issue separate permanent guidelines later this year. The cancer society doesn’t issue joint guidelines or endorse other group’s guidelines, Brawley said.

“Screening is a double-edged sword,” Brawley said. CT screening prevented about 80 lung cancer deaths over six years in the National Cancer Institute study, but 16 study participants died after CT screening, including six who did not have lung cancer.

Brawley and Bach expressed concern about heavy marketing by some centers that overstate benefits from CT lung cancer screening and that recommend the scans for low-risk patients.

Screening nonsmokers and other low-risk patients “will cause more harm, and yield less benefit for the simple reason that ... they’re so much less likely to get lung cancer in the first place,” Bach said.

Brawley noted that some centers charge at least $300 for these scans, which often aren’t covered by insurance, particularly for low-risk patients.