(January 11, 2013)--The American Cancer Society says there is now enough evidence to recommend lung cancer screenings for certain older, heavy smokers.

The society was releasing new guidelines Friday for annual CT lung scans, which are only recommended for people ages 55 to 74 who have smoked a pack of cigarettes a day for 30 years or the equivalent, such as two packs a day for 15 years.

Research shows that screening these people can cut the risk of dying of lung cancer by 20 percent.

Whether screening would help others is not known, so scans are not recommended for them.

Before patients decide whether to be screened, the guidelines say they should have a frank talk about risks and benefits with their doctors.