Future Horizons in Lung Cancer
How to avoid false positives in lung cancer
Dr Claudia Henschke - Mount Sinai Hospital, New York, USA
I talked about CT screening for lung cancer and with a particular focus on how to keep the false positives down. First of all you have to recognise that the CT scan provides information about the entire chest, so there’s a lot of additional information other than just lung cancer. You learn about cardiac abnormalities, you see mediastinal abnormalities, you see other diseases in the lungs that are not lung cancer but are potentially treatable and certainly important for the person to know that they have.
First of all you have to define false positives. When you see something on any study you should report it. What you have to be careful about is how you do the follow-up, what do you do when you see something. If you see a nodule, knowing a lot about screening CTs, you know that certain sizes are not important, certain appearances are not important, so just the fact that you see a nodule doesn’t meant that you have to act on it. So the purpose of my talk was to point out that you have to know when you see it, you have to know what you’re seeing and the subtypes of nodules, which ones could be aggressive cancers, which ones are not. By doing that carefully you really don’t do unnecessary work-up in a lot of people. It can be as low as 10% and perhaps even lower; you’re getting a lot of additional information from that CT scan.
Are there any guidelines for this kind of assessment?
Based on our database, which is the largest database in the world, of more than 75,000 people and we’ve looked at screening over a long period of time with long-term follow-up, we have our recommendations for what we call a positive result of screening and what the work-up should be. That’s published on the website, on our website, and it’s something that we update, we talk about and we look at the data every six months, we update as we need to update and that’s an important part. So you want to go to somebody who has guidelines for what should be called positive, what should have further work-up and a group that also updates and regularly reviews the data to make sure that as new techniques are introduced that they’re looked at.
Are you seeing correlations between other diseases and cancer?
The correlation between lung cancer and heart disease is there’s a common aetiology of smoking but there are also other causes of lung cancer. A lot of people who have never smoked also have lung cancer and people who have never smoked have coronary artery disease. So it’s a hard thing to answer succinctly but there are certainly relationships.
Is there a correlation between emphysema and lung cancer?
Clearly when you see on your CT scan you see emphysema, first of all I talk to patients about it because if they’re currently smoking they really should know that they have emphysema because they can stop the progression by quitting to smoke. Even the ones who quit smoking quite a while ago, if they have emphysema it’s important to talk to them about it. Clearly the more emphysema you have the higher risk you are of lung cancer and if you have severe emphysema you’re probably at six times the risk of lung cancer. But the majority of people that you see in a screening programme that are found to have lung cancer do not have emphysema so you can’t just screen the people that have emphysema because still many have lung cancer when there’s no evidence of emphysema or COPD on their CT scan.
The aetiology of lung cancer is a difficult thing. I don’t think that’s been really determined but there is probably a role of chronic inflammation, there’s clearly the cause of emphysema is predominantly from smoking or inhalation of toxic substances. Asbestos certainly creates a higher risk of lung cancer but it really doesn’t create emphysema per se. So all of those relationships, probably as screening information develops more and more and as the genetics is studied more and more, will have more information. There’s clearly a relationship but some have said that if you smoke some people tend to get emphysema and lung cancer and some people tend to get coronary artery disease and it’s not quite the same pathway.
What is your take home message?
The conclusion of my talk was that you really have to have a well-defined approach to how you interpret the data and what you recommend for follow-up. We call it a regimen of screening, so it’s how you obtain the CT scan, how you define a positive result that requires further work-up and then what that further work-up should be. For the most part there really shouldn’t be any invasive work-up unless you’ve demonstrated growth and in that case there shouldn’t be unnecessary surgery or the percentage that have surgery for benign disease should be quite low and some of the other data reported at this meeting showed it could be well below 10%. So ultimately you would say that a false positive is somebody who you see something on the CT scan and who goes to surgery who didn’t need surgery and that should really be kept quite low. It can be less than 5% of the people.
