Two new analyses come to differing results regarding who should get screened for lung cancer.
The National Lung Cancer Screening Trial provided strong evidence that screening for lung cancer with low-dose CT scans can reduce deaths.
Since then, the inclusion criteria of that trial have entered into national guidelines regarding who should get screened. And here are those guidelines:
These criteria would capture around 7 million Americans. If we screened all of them, we’d save around 32,000 lives.
But a couple of new analyses, appearing in the Annals of Internal Medicine, raise some interesting questions. We’ll tackle them in order.
First- are these criteria too simple? We have a number of statistical models that can quite accurately predict lung cancer risk. Why not just screen the highest risk people?
In an analysis using data from a representative health survey, Li Cheung and colleagues found that there is a substantial population of individuals at relatively high risk of lung cancer who wouldn’t fit under the current guideline’s umbrella. Here's the risk for a hypothetical 60 year old with a 25 pack-year history but also with emphysema and a family history of lung cancer under various models.
The authors found that screening individuals with greater than a 2.5% risk of lung cancer over five years would save a bit more than 5000 additional lives.
But risk-based screening has some drawbacks. In a second article in the same Annals issue, David Kent and colleagues point out that risk-based screening is complicated – it requires a practitioner plugging a bunch of numbers into a computer program to get a risk score out at the end. We can do that – we do it for things like breast cancer – but it’s an added hurdle.
The other issue they bring up is that the benefit of saving one life in a higher-risk group is not the same as saving one life in a lower-risk group. It sounds cold, but people at high-risk of lung cancer are at high risk of a lot of things, and tend to have a reduced self-reported quality of life. In other words – catching an early lung cancer in a high-risk individual might not provide as much bang for the buck as catching one in a low-risk individual.
In the end, Kent’s group finds that screening high-risk individuals is a bit more cost-effective in terms of quality-adjusted life-years saved, but not drastically so. Screening low risk people costs around $75,000 per quality-adjusted life-year saved, compared to $53,000 for screening high-risk individuals. These are both below the $100,000 per quality-adjusted life year threshold that many payers consider… well… worth it.
The conclusion? Screening based on the simple guidelines is probably fine.
But honestly the biggest question to me is why are our screening rates so low. Of the 7 million eligible individuals, just 74,000 (about 1%) got screened last year. Maybe the question isn’t what model we should be using to decide who to screen, but how we should convince doctors and patients that screening is actually a good idea.