Who should get screened for lung cancer?

Using chest scans to screen for lung cancer in people who've never smoked and have no symptoms might help catch cancers early and decrease the disease's death toll, suggests a new study from Japan.

But experts say the findings likely don't apply in non-Asian countries, where the majority of all lung cancers are found in people who smoke - and where using computed tomography (CT) scans to screen for lung cancer in smokers has recently been a controversial topic.

Moreover, they warn that while regular screening might help doctors catch cancer earlier, it also comes with a high price tag and added risks to patients.

CT scanning uses X-rays and computers to produce a clearer image than traditional X-ray techniques, but CT also uses higher radiation doses to generate those images.

Everybody agrees that CT "does find the early stage lung cancer," said Dr. Heidi Roberts, a lung cancer researcher from Women's College Hospital, Toronto who wasn't involved in the new study. Early-stage cancer is easier to treat and has a higher survival rate.

The new study provides further evidence of that. Researchers led by Dr. Ryoichi Kondo of Shinshu University Hospital in Matsumoto looked back at outcomes for close to 500 non-smoking lung cancer patients whose cancer was caught by CT scan screening, or by standard X-ray screening - another strategy for catching cancer early - or when patients came into the doctor with lung symptoms.

Most of the tumors found via CT scans were small, whereas those found through X-ray screening or in patients with symptoms were more often further advanced, according to the findings published in the journal Lung Cancer.

Five years after their diagnosis, 95 percent of people whose cancers were found through a CT scan were still alive, compared to 73 percent diagnosed with an X-ray and 40 percent of patients who had not been screened and whose symptoms led to discovery their disease.

East Asian countries are more likely to regularly screen non-smokers for lung cancer because biological differences seem to put Asians at a higher risk than other non-smokers, researchers explained.

Non-smokers without symptoms generally are not screened for lung cancer in the U.S.

There and in Canada, the lung cancer debate has centered around how often to screen smokers, and until what age screening should be done, Roberts said.

In another study published by Kondo and colleagues - this one looking at lung cancer screening in smokers - five-year survival rates were also highest in those screened with CT scans.

That's consistent with the findings of the National Lung Screening Trial in the U.S., which in November released data - published online in the New England Journal of Medicine last week - showing that 20 percent fewer middle-aged heavy smokers died of lung cancer when they were screened annually with a CT scan compared to a standard, less detailed chest X-ray.