CT Screening for Lung Cancer: A Study in Cost-Effectiveness

Andrew F. Shorr, MD, MPH


January 22, 2015

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This is Andy Shorr from Washington, DC, with the pulmonary and critical care literature update. Today, I want to discuss an article in the November 6 issue of the New England Journal of Medicine by Black and colleagues.[1]

These authors investigated the cost-effectiveness of CT for lung cancer screening. More than 3 years ago, the National Lung Screening Trial[2] indicated that, compared with chest x-rays, low-dose, routine CT scanning could save lives and prevent deaths related to earlier detection of lung cancer.

In that analysis, the number needed to treat seemed high, at about 217. In addition, the number of patients who were harmed was not insignificant in terms of patients needing workups for nodules that were benign. Moreover, the risk for death or surgical complication was relatively low, which was one of the reasons the trial was criticized in terms of its inability to be generalizable to the rest of us in the real world.

However, since those analyses were published, other studies[3,4] have indicated that we can stratify the risk for lung cancer relatively well based on data from that trial. In fact, we can divide patients into quintiles of risk, from lowest risk to highest risk groups, based on easy-to-identify risk factors.

Advancing the Debate

The work by Black and colleagues[1] advances the debate even further. The Centers for Medicare & Medicaid Services chose not to reimburse for this approach to preventing death from lung cancer even though they pay for a number of other ways to screen for lung cancer and we have a well done, randomized, controlled trial supporting the value of this approach.

These authors tried to model the cost-effectiveness of using the CT scan approach vs the chest x-ray approach or no screening to determine how much more CT screening costs to save 1 year of perfect health. This is, in some ways, a mathematical modeling exercise because there is no such thing as a year of perfect health. If I want to compare the value of one intervention of medicine to another, however, I need to find some common denominator or common language. Generally, from a cost perspective, the output that we measure is called a quality-adjusted life year; in other words, 1 year of perfect health. You can assess that based on how long you think someone is going to survive, what the quality of that life will be, and the costs associated with that related to, for example, the intervention, the surgeries, and so on when you use that screening approach.

In this analysis, the authors were meticulous. They relied on data from the actual clinical trial and estimated that to save 1 year of perfect health (or 1 quality-adjusted life year), the theoretical cost to society would be approximately $81,000. The current accepted threshold for cost-effectiveness, which is necessarily arbitrary, is approximately $100,000 per quality-adjusted life year.

Thus, based on the model data and the data from the clinical trial, these authors estimate that overall this would be a cost-effective strategy. From a policy perspective, Medicare should want to focus on this.

Important Insights

I believe some issues and insights into this trial are important. First, these investigators did not look into the concern many people had about the low risk for surgical complications in patients undergoing some kind of surgical intervention in the original trial. It is not clear how sensitive their model is to this kind of concern. If the risk for a surgical complication goes up and the cost or consequences associated with that surgical complication go up, that cost-effectiveness ratio may begin to change. The difference between $100,000 and $80,000 is not large and could potentially be crossed if you had a few more surgical complications or they were more expensive than you anticipated.

Second, clearly screening is more cost-effective in selected populations. This is particularly true for women because they tend to have different subtypes of lung cancer that are more easily detected by CT scanning than lung cancers in men and in older patients generally, although that was not a uniform relationship. There seemed to be a sweet spot in terms of cost-effectiveness in older patients.

Screening too many younger patients who have not had time to develop lung cancer is not particularly cost-effective. Screening too many older patients is not particularly cost-effective because they may not have as many years of life left.

Similarly, the study found that as the risk for lung cancer went up, cost-effectiveness went up. That was not a perfect relationship, however. The authors speculated that this may have reflected the sample size of their various cohorts. It generally suggests that we can be more precise and more finely tuned.

In the end, we need to decide as a society how we are going to take on lung cancer screening, and this article is important. As clinicians, we generally do not read cost-effectiveness literature, but this is a well done study, and I would encourage pulmonologists to look at it so they can be more informed for this debate.

This is Andy Shorr from Washington, DC.


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