After decades of qualms about lung cancer screening, the American Cancer Society says there now is enough evidence to recommend it, but only for current and former heavy smokers ages 55 to 74 and after a frank talk about risks and benefits.
The new guidelines, announced Friday, are a cautious but exciting step against the world’s most deadly cancer, doctors who wrote the advice say.
It is based on a big study in 2011 that found annual, low-dose CT scans — a type of X-ray — could cut the chances of dying of lung cancer by 20 percent and from any cause by nearly 7 percent.
The study only included older people who smoked a pack of cigarettes a day for 30 years or the equivalent, such as two packs a day for 15 years.
Whether screening would help others isn’t known, so scans were not advised for them.
‘‘We’re trying to make sure we restrict harm that might come from screening,’’ such as unneeded biopsies and follow-up procedures when scans falsely suggest cancer, said Dr. Richard Wender, family medicine chief at Thomas Jefferson University in Philadelphia.
Lung cancer is fairly rare in people who are younger than 55, so ‘‘the benefits of screening are going to be less if you start at a younger age,’’ Wender said.