WASHINGTON — Certain current or former heavy smokers should start getting yearly scans for lung cancer to cut their risk of death from the nation’s top cancer killer, government advisers said Monday — even as they stressed the tests aren’t for everyone.

The long-anticipated decision by the influential U.S. Preventive Services Task Force says these CT scans of the lungs should be offered only to people at especially high risk: those who smoked a pack of cigarettes a day for 30 years or an equivalent amount, such as two packs a day for 15 years — and who are between the ages of 55 and 80.

That’s roughly 10 million people, but not all of them qualify for screening, said task force vice chairman Dr. Michael LeFevre, a University of Missouri family physician. Even those high-risk people shouldn’t be scanned if they’re not healthy enough to withstand cancer treatment, or if they kicked the habit more than 15 years ago.

Lung cancer kills nearly 160,000 Americans each year. Smoking is the biggest risk factor, and the more and longer people smoke, the higher their risk. Usually, lung cancer is diagnosed too late for treatment to succeed.

The newly recommended screening could prevent as many as 20,000 deaths a year, LeFevre said — if it’s used correctly.

That estimate assumes good candidates seek the scans. There’s no way to know if people at the highest risk will, or if instead the overly anxious will flood testing centers.