Posted: Thursday, October 27, 2011, 7:50a.m.

A major government study is challenging a once-common type of screening for lung cancer.

The study of more than 150,000 older Americans shows routine chest X-rays do not prevent lung cancer deaths, not even in smokers or former smokers.

The study found those who had four annual chest X-ray screenings were just as likely to die of lung cancer as participants who didn't have those tests.

The results from the National Cancer Institute-funded research confirm previous, smaller X-ray studies. They follow another big study from that institute favoring a newer, more sophisticated imaging test.

That study found fewer lung cancer deaths among current or former heavy smokers who had special CT imaging scans.

CT scans provide much more detailed images and while no major medical group recommends any type of routine lung cancer screening, several are preparing new guidelines.