Monday, June 06, 2005

New Study Promotes CT Screening as Smoking Cessation Tool

A study in the April 15 issue of Cancer reports that abnormal CT scans obtained as part of a three-year study of the utility of screening for lung cancer among smokers served as a motivational tool that increased smoking abstinence among these patients. Among smokers receiving annual chest CT scans for the early detection of lung cancer, 42% who had three successive abnormal scans quit smoking, compared to 28% with two abnormal scans, 24% with one abnormal scan, and 20% with no abnormal scans. Receiving a recommendation the previous year for follow-up due to an abnormal CT scan finding was significantly associated with smoking cessation.

The authors conclude not only that increased positive findings on chest CT screening increase smoking cessation, but that overall, the use of this type of screening enhanced smoking cessation rates, as “abstinence rates for those receiving 1, 2, or 3 positive screenings are much greater than the expected annual abstinence rates of 5-7% found in the general population.”

The paper’s overall conclusion is that: “Better understanding of the predictors of smoking cessation, including multiple lung CT scans, may inform the debate on the use of screenings for early-stage lung carcinoma to increase smoking abstinence… .” The authors note that: “The cost of annual lung CT scan screenings will have to be weighed against the potential benefits of increased smoking abstinence rates in high-risk populations of smokers.”

The Rest of the Story

On the surface, this may appear to be convincing evidence that supports the use of chest CT scanning of smokers as a motivational tool to encourage smoking cessation. However, closer consideration of the study reveals a number of very concerning issues.

First, at the most basic level, this study does not provide evidence that annual CT scanning of smokers, in itself, enhances smoking cessation. The paper compares the rate of smoking abstinence among study participants (which was about 20% at three year follow-up for smokers with normal CT findings) with rates among the general population of smokers (which are only 5-7%). However, this is not a relevant comparison. A relevant comparison would be with smoking abstinence rates among smokers who are highly motivated to quit, so motivated that they enroll in a lung cancer screening study.

In other words, the very fact that all subjects in this study were motivated enough to enroll in an intensive, long-term study to specifically screen for lung cancer makes them a special population, and comparing cessation rates among this group to population cessation rates makes little sense. So the absolute finding of “high” rates of smoking cessation in this study is not particularly meaningful.

Second, the study finding that being told that one has a suspicious lung nodule that needs follow-up motivates people to quit smoking is actually somewhat disturbing. Why? Because the overwhelming majority of these nodules are not, in fact, malignant. According to the most recent published data from this Mayo Clinic study, 92% of abnormal chest CT findings in this study are benign. What this means is that it is largely false positive results that are motivating quitting behavior. Smokers are quitting, therefore, based on a largely false belief that they may have lung cancer.

In and of itself, this is not necessarily a bad thing; however, to recommend the use of CT screening to promote smoking cessation is essentially promoting the use of instilling false fears in patients in order to motivate a change in a health behavior. That I have serious problems with.

Third, and most importantly, this study seems to suggest that a finding of increased cessation among smokers who are screened via annual chest CT supports the use of this strategy. But I don’t find that to be relevant to the consideration of using chest CT as a medical screening tool. If chest CT scanning is to be justified, it is going to have to be justified entirely on the basis of being an effective screening tool. If it is not justified on the basis of being an appropriate screening technique, then the benefits that may accrue to patients in terms of smoking cessation certainly do not justify the widespread use of this screening strategy.

The paper speaks about a “debate on the use of screenings for early-stage lung carcinoma to increase smoking abstinence.” I find that disturbing, because I don’t think there should be any such debate. We should absolutely not be using CT screenings as a strategy to increase smoking cessation. That is simply not an appropriate use of a medical screening procedure.

I have several serious ethical concerns with the approach to the evaluation of chest CT screening suggested in this paper. Is it ethical to promote a strategy for smoking cessation that relies largely upon instilling false and inappropriate fears among patients to motivate them to change their behavior? Is it ethical, in the first place, to use a medical screening procedure (that is designed for the early detection of disease) as a health behavior change strategy?

I can imagine, for example, that giving all 20-year-olds a colonoscopy might be an extremely effective strategy to change health behaviors (such as fiber intake and fat intake) that may be risk factors for colon cancer. Giving 18-year-old smokers a bronchoscopy would almost certainly induce a large number of them to quit. But these strategies are not ethical, because they are simply not justified as screening procedures.

My point here is not that chest CT scans will not eventually turn out to be justified as a lung cancer screening tool (although see my previous posts [post1 post2] about why there is not evidence at this time to justify CT screening for lung cancer). Instead, my point is that whether CT scanning increases smoking cessation is not relevant to the consideration of this strategy as a medical screening procedure. If it is justified, then it must stand on its own as a screening strategy, not on the basis of any effect on health behavior change.

So I disagree with the paper’s contention that “The cost of annual lung CT scan screenings will have to be weighed against the potential benefits of increased smoking abstinence rates in high-risk populations of smokers.” That is not an appropriate consideration. Even if the costs are outweighed by potential benefits of smoking cessation, the use of annual lung CT scans is not justified, appropriate, or ethical if it is not determined to be an effective and appropriate medical screening technique.

The rest of the story suggests that the appeal of advanced, state-of-the-art, high-technology solutions to society’s problems may be clouding the judgment and decision-making framework in the medical profession, and if left unchecked, could eventually result in the inappropriate and potentially unethical promotion of a costly, intensive, and fear-producing medical procedure.

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