WCLC 2025 | Smoking behaviors in the Yorkshire Lung Screening Trial (YLST)

So we were interested in what impacts an invitation to lung cancer screening has on someone’s smoking behaviour. There’s really two ways this can go. It may be that someone is invited for screening, they have a normal scan, which most people will, from a screening programme. But this gives them the opportunity to think about their respiratory health. And if they are a current smoker, to think about whether or not they might quit. And so by providing smoking cessation services alongside screening, the hope is that you can get people to quit who might not otherwise have done so. So that’s called the teachable moment. And so there’s a real hope that lung cancer screening will be a teachable moment. That’s what we want. But there’s an alternative scenario, and that is that someone might have been thinking about quitting. They come and get a CT scan done. It’s clear, and then they think, well, maybe I don’t need to quit after all. Maybe I’m being protected in some way. Maybe I’m just lucky and I’m avoiding the downside of smoking. So there’s a possibility that by screening people, we might actually end up with more people smoking than we would have done without a screening program. And that’s called the license to smoke effect. So these are two possible competing effects. And there’s been research on this previously from some of the randomized studies and that’s shown different outcomes. Some suggest there might be a license to smoke effect. There’s some qualitative work that suggested that up to 50% of people who currently smoke might take some reassurance from a normal scan in terms of their smoking behavior. So that’s quite a concern. So in our study, what we did is we looked at 45,000 people who we invited to our lung cancer screening program, but there was a similar number, a randomized group who we left alone and we never got in contact with. They were our control group. And so really, this is the best way to be able to see what the net effect is because you’ve got a group that you completely leave alone and then a group you invite to screen. What we found is that the number of interactions with smoking cessation services was about four times higher in the group invited for screening versus the group that was left alone. And the quits were between two and four times higher in the group that came for screening. So I think our data has demonstrated, I think, that there isn’t a dominant license to smoke effect and that screening is a teachable moment, which is a really great result, I think.

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