Thursday, August 18, 2005

In Wake of Peter Jennings' Death, Many Recommending CT Screening for Lung Cancer in Ex-Smokers

In the wake of Peter Jennings' death from lung cancer caused by smoking, a debate over the usefulness of CT scans as a screening tool for lung cancer in current and ex-smokers has emerged.

The argument in favor of using chest CT scans for lung cancer screening in current and ex-smokers is that this procedure can detect tumors far earlier than they are normally detected (based on the appearance of symptoms or the appearance of tumors on conventional chest X-rays). With earlier detection, definitive treatment for lung cancer is more likely to be possible, resulting in a reduced death rate from the disease.

The argument in opposition to using chest CT scans for lung cancer screening is that there is not yet any documented evidence that the procedure will save lives yet there is substantial evidence that the procedure will result in a large number of false positive tests, creating widespread anxiety among patients and requiring the use of additional screening or in some cases, invasive and risky diagnostic procedures. In addition, there is no evidence that the benefits of the use of this procedure as a screening tool would outweigh the costs (estimated at $39 billion on a national basis).

The Rest of the Story

Although it would be tremendously beneficial for there to be an effective screening test that could detect lung cancer at an early and treatable stage, there is unfortunately no such screening test presently available.

First, there is as yet no published evidence that spiral CT scanning is effective in reducing mortality from lung cancer via the early detection of tumors at a treatable stage. Until such documentation is available, it would be premature to recommend this procedure as a screening test on a population level.

Second, the false positive rate is currently far too high to make spiral CT scanning effective and appropriate as a population screening tool. Use of such a screening procedure on a population basis would result in millions of patients with false positive results, creating widespread anxiety, requiring intensive follow-up screening, and in some cases, necessitating the use of invasive and risky diagnostic procedures.

Third, because of the first two problems, it is not at all clear that the cost of population screening for lung cancer among smokers and ex-smokers would be outweighed by the potential benefits.

In summary, there is simply no justification at the present time to support the recommendation for chest CT scanning on a population level for screening for lung cancer among current smokers or ex-smokers.


Cantiloper said...

I have several comments on the use of CT scans for early detection of lung cancer.

First of all, Mike's observation about the lack of documentation about the value of the tests is accurate, but the only way we'll ever GET that documentation is through further testing! :> I'd agree it's too early to talk about a national tax-paid-for program, but on the individual level it's a different story.

As for the concern about false positives creating needless anxiety and unnecessary (and sometimes destructive) procedures: This could be corrected for easily by a simple standard requiring that unless a clear tumor (by some set standard) is detected, that providers be forbidden from sharing the results of the test for a period (?six months?) with the patient.

This would be required for all results showing nothing or showing "possible" problems. Six months down the line the patients would be notified that they either tested "clear" or tested as a "possible problem." At that point a second CT should be able to confirm whether any "possible problems" were real by seeing if the anomoly in the original scan is still there at all or has even actually grown.

If it is still there, particularly if it has grown, then the chances of the positive being "false" might be indicative enough to suggest further procedures. (Note: I am *not* a doctor... not even a mechanical engineer... and I haven't read more than a few articles on this topic, so take my words here with the appropriate grain of salt. I'd be quite happy to see some real doctors weigh in with their thoughts as well!)

As for expense... if the procedure comes into more common use the per-patient expense would decrease. It's also likely that over the next few years the accuracy of results is likely to improve as well. Thus I certainly don't think that this type of testing should just be thrown out with the bathwater because things aren't perfect yet.

Michael J. McFadden
Author of Dissecting Antismokers' Brains

Cantiloper said...

A few further late night thoughts that I feel might be appropriate to spark thought and discussion here... please forgive any inaccuracies in my figuring, it IS 4am here at the moment. :>

According to data from the Franciscan Health System

only about 5% of lung cancers occur before the age of 50 or so. If we assume that roughly 10% of smokers will eventually get lung cancer (this figure may not be exact, but I believe it's in the ball park) and we combine that figure with the 5% before age 50, this would lead us to a rough figure of about 1 smoker in 200 developing it before age 50. Even if our figuring is underestimated by 100% we'd still be catching 99 out of 100 cases if detection were perfect.

Thus it wouldn't be unreasonable to screen only smokers and ex-smokers over age 50. If we further limited our screening for the cohort extending from age 50 to 59 to only moderately heavy smokers who had not quit decades previously, the screening population would be even further reduced.

Rather than being faced with a task of screening 160 million people, a targeted CT screening program aimed at picking up 80% or 90% of Stage I and II lung cancers might only have to cover a quarter of that: 40 million people. This would lower the cost to $10 billion while achieving most of the desired goal.

The bulk of the MSA money illegally taken from smokers by the compact between multiple states and Big Tobacco was supposed to go into "covering the health costs of smoking" (Although, oddly enough, many states independently have justified all sorts of other tax increases on smokers with the same excuse... the math is reminiscent of that which claims 50% of kids smoke because of movies.)

Why don't we simply take the MSA money, including the funds spent on all the executive salaries of Antismoking Lobby group leaders, and invest it in a program likely to save the lives of the smokers it's being taken from? (Especially since, after accounting for the influence of movies, peer pressure, parental modeling, tobacco advertising and hangnails it would appear that Antismoking funding has very little to do with kids' taking up smoking.)

Or would this be too sensible?

Michael J. McFadden
Author of Dissecting Antismokers' Brains