Lung cancer screening has been an area of considerable controversy.  Before today, there had been no evidence that screening patients for lung cancer, either with a CT scan or chest x-ray, saved lives.

For years, doctors have been waiting for the results of the large, randomized National Lung Screening Trial (NLST), conducted by the National Cancer Institute.

This morning, it was announced that the trial was stopped early, with a bold, positive finding:

All participants had a history of at least 30 pack-years, and were either current or former smokers without signs, symptoms, or a history of lung cancer.

As of Oct. 20, 2010, the researchers saw a total of 354 deaths from lung cancer in the CT group, compared with 442 in the chest x-ray group.

That amounts to a 20.3% reduction in lung cancer mortality — a finding that the study’s independent data and safety monitoring board decided was statistically significant enough to halt the trial and declare a benefit.

Previously, only breast, colon, and cervical cancer has had the evidence back up its screening recommendations. It’s still early in the game, but it appears that lung cancer may be following in that same path.

That said, there are a variety of concerns before opening up the floodgates to screening chest CTs.

First, participants in the study were limited to former or current smokers — not the population at large.

Second, there remains a concern about the risk of cumulative radiation exposure that an annual chest CT will bring. We are in the midst of an informational push to educate the public about the dangers of radiation stemming from diagnostic imaging. Will this news, sure to be played loudly over mainstream media, only increase the demand for CT imaging?

And finally, there is the concern about incidentilomas that screening CTs will bring. Incidental findings that result from a screening CT may necessitate further workup that may only confirm a benign condition. Furthermore, these tests tend to be more invasive — like a biopsy, for instance — which can put the patient at harm.

Today’s news has the potential to fundamentally change lung cancer screening guidelines sometime in the future. If future studies corroborate the findings, perhaps lung cancer screening targeting smokers may be instituted within the next few years.

Until then, the first line of defense against lung cancer is to quit smoking. That message shouldn’t be lost in the hype that is sure to follow today’s news.

Kevin Pho is an internal medicine physician and on the Board of Contributors at USA Today.  He is founder and editor of KevinMD.com, also on Facebook, Twitter, and LinkedIn.