updated 12/20/2005 5:36:07 PM ET 2005-12-20T22:36:07

Use of routine chest X-rays to hunt lung cancer leads to frequent false alarms, but when tumors are found they tend to be early-stage, say preliminary results of the biggest study ever to address lung-cancer screening.

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The next question is whether this screening leads to fewer deaths. An answer is still several years away.

More than 172,000 Americans will be diagnosed with lung cancer — the nation’s top cancer killer — this year. Most will die within two years because this stealth cancer almost always is diagnosed at advanced stages. If lung tumors are caught early, five-year survival skyrockets, but there is no proven early-screening method.

Studies during the 1970s concluded that X-ray screening didn’t save lives, either because it didn’t catch the deadliest tumors soon enough or it needlessly put patients with slow-growing tumors through risky surgery and other treatments.

Now, X-rays are being put to the test again in a government-sponsored study of more than 150,000 seemingly healthy 55- to 74-year-olds. Half were given annual chest X-rays; the rest received no screening.

Of the more than 77,000 people screened, doctors spotted something suspicious on the X-rays of 5,991, almost 9 percent, researchers reported Tuesday in the Journal of the National Cancer Institute.

Patients were sent back to their regular doctors for repeat X-rays, CT scans or other evaluations, and 206 wound up undergoing a biopsy.

Ultimately, 126 people were diagnosed with lung cancer — 2 percent of the initially suspicious X-rays.

Importantly, 44 percent of the cancers were in the disease’s earliest stage, noted lead researcher Dr. Martin Oken of Minnesota’s Hubert H. Humphrey Cancer Center.

But that’s a lot of false alarms, cautioned Dr. Christine Berg of the NCI, which is sponsoring the study. So-called false-positive results can bring more than needless anxiety and high health bills; a biopsy sometimes causes a collapsed lung.

The study is tracking the newly diagnosed cancer patients to determine if early detection reduces deaths enough to warrant the false alarms.

“That risk may be worth taking if you knew the lung cancer that could potentially be detected would be caught at an early enough stage to potentially save your life,” Berg explained. “But lung cancer is an extremely aggressive disease, unfortunately, and we need to prove that we can have an impact on mortality.”

Why revisit X-rays? Partly it’s because smokers today tend to get a different form of cancer, called adenocarcinoma, than they did before filtered cigarettes became popular in the 1970s — and modern X-rays might spot those tumors more easily.

Many scientists are betting that a more expensive test, called a spiral CT scan, will prove a better screening tool. A separate government study is under way comparing X-rays with spiral CTs — although the $300 test already is in high demand, as many smokers and former smokers aren’t waiting for the evidence.

Lung cancer occasionally strikes people who never smoked. Surprisingly, 14 of the 126 cancer diagnoses in Tuesday’s study were among people who had never smoked — and they accounted for more than 40 percent of the initially suspicious screenings.

© 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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