Screening for lung cancer with a CT scan: What the NLST results mean

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.

 is an internal medicine physician and on the Board of Contributors at USA Today.  He is founder and editor of, also on FacebookTwitterGoogle+, and LinkedIn.

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  • MassachusettsPCP

    “The middle-aged and elderly smokers were scanned with either three spiral CTs a year or one annual chest X-ray starting in August 2002. They were followed for five years.”

    OK. So I do put in a prior authorization 3x/year for a spiral CT for a 30+ pack year smoker (in addition to advising patient to stop smoking)? If I don’t have I been negligent? Will once/year suffice? In my state, the plaintiff can sue for “loss of time from life”, a loose term that means that even if the cancer was picked up, if it was picked up late enough NOT to mean the difference between life and death but still impacted duration of life expectancy it is grounds to sue. And we already know many lung cancers present with vague, nonspecific findings .. not the classic weight loss, chronic cough, malaise, and hemoptysis that is textbook. I guess the insurance companies and/or USPHTF needs to make a guideline for how often. Perhaps once/year just as we do abdominal ultrasounds in smokers, unless symptoms warrant.

  • jim m.d.

    Great idea! Let’s consume more health care dollars, do more testing, and assume more liability for those who selfishly, and self-indulgently engage in a behavior which is a direct cause of this disease.
    Better idea: Smoke all you want (freedom of choice), but in order to purchase tobacco you must first present a “tobacco user ID.” In order to get said ID you must be age of majority and sign a release that you will assume all financial responsibility for any diseases resulting from tobacco use. ID # is part of your permanent medical record. Then let’s see how many smokers want to pony up their hard earned dollars for this screening.
    When will we stop enabling this self-destructive behavior?

  • Elaine Schattner, M.D.

    I agree completely. Smoking cessation would be far superior, less costly and also preventive of other smoking-associated illnesses like vascular disease, than repeated CT scans.

  • SarahW

    Smoking cessation is well and good, but you have to examine/treat the patient you have, not the one you want.

    Offering help for stopping smoking also does not help former heavy smokers who have quit.

    WIth regard to incidentalomas, patients should be made aware of that risk as well as the near certain but not fully quantififed risk of repeated CT’s, which could cancel out the diagnostic advantages. Then the patient should choose to take or reject the risk, not the physician.

    Who pays is not your concern. The practice of medicine and improving the lot of individuals is your concern.

    • Justin

      The cost of 3 CT scans a year and who pays is not the concern of the individual physician dealing with the patient in front of her/him. However, it is the concern of everyone who pays insurance premiums which are already high because of poor life choices.

      I think the above posts are alluding to the fact that if people were held responsible for their choices (eg making smokers pay for cancer screening IF they wanted it), people would make healthier choices for themselves.

  • Michael F. Mirochna, MD

    I’m going to buy a low-dose spiral CT and then retire.

  • Marc Gorayeb, MD

    Please, people, let’s set the record straight on how the study was actually conducted. Below is a quick summary of the actual study.
    “In September 2002, the NCI launched the largest lung cancer screening study ever conducted. The National Lung Screening Trial, or NLST, compared the effects of two lung cancer screening procedures, low dose helical CT and chest X-ray, in reducing mortality in current and former heavy smokers aged 55 to 74. Unlike previous trials, the NLST was a randomized control trial, the gold standard in clinical trials. Participants were randomly assigned to one of two comparable groups – chest X-ray or helical CT – and received THREE ANNUAL SCREENINGS based on their assigned technology. The groups were followed for at least five years beyond the final screening.”

    The source:

  • Glenn Laffel, MD, PhD

    This is a potentially exciting development, but my instincts are to sit tight and wait. The write-up of the study hasn’t even been published in a peer-reviewed journal yet!

    What is more, the cost-effectiveness of Spiral CT isn’t clear even with these findings…and it’s likely to be astronomically high given that there was (apparently) a 25% false positive rate in the CT group. Imagine the costs associated with all those extra CT scans, ancillary tests and perhaps even thoracotomies to chase these false positive findings down.

    My guess is that this’ll settle out to where the CT scans are considered wise in older adults (say >65) with a hx. of heavy cigarette consumption. These are the people who are at highest risk for developing lung cancer, and at the lowest risk from the consequences of cumulative exposure to radiation associated with the CT scans themselves.

    Glenn Laffel, MD, PhD
    CEO, Pizaazz

  • Michael Eliastam

    I really do not understand why the trial wa sstopped; this sounds like PSA testing where the ‘benefit’ turns out to be an illusion, but only after more data is collected etc.
    Now the greedy ones with neighborhood trucks carrying scanners have been given ‘support’ of dubious value. Why do academic doctors who manage such research allow this rush to judgement when we know what the long term outcome is likely to be? We have seen the enemy……………

  • gzuckier

    “I really do not understand why the trial wa stopped”
    Well, that’s standard for clinical trials; if it becomes sufficiently clear early on in the trial that the treatment is beneficial, it is unethical to continue withholding it from the control population on the off chance that it will turn out to be a fluke. (Even though .05 level of significance means that 1 positive result in 20 will indeed be a fluke). Likewise, but vice versa, if it becomes clear early on that the treatment is harmful.

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