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Limitations in Screening for Lung Cancer
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Limitations in Screening for Lung Cancer

Philippa Cheetham, MD, and Kim L. Sandler, MD, remark on the challenges faced while interpreting imaging scans that are used to help diagnose lung cancer.
PUBLISHED November 13, 2017


Transcript: 

Philippa Cheetham, MD: Welcome back to CURE Connections®. We have a very esteemed panel here today for this segment. We’re talking to Dr. Sandler about imaging for lung cancer, to Dr. Osmundson about radiation for lung cancer, and to Dr. Horn, who specializes in the medical treatments for lung cancer. This is a very exciting time, not just for lung cancer but also for many other cancers. The imaging is where it all starts. We know that patients are being screened now. Thankfully, we have a national screening program. What are the interesting new technologies that are coming in to imaging that are helping you detect lung cancer earlier for patients?

Kim L. Sandler, MD: I think one of the greatest things about our new scanners is that the dose is so much lower than the scanners we were using 10 or 20 years ago. We are now using a fraction of the amount of radiation to obtain the same information. We can also do what are called “dual-source CT scanners.” So now, rather than just having 1 source of radiation and 1 detector, we have 2 that acquire images at the same time. Rather than increasing the amount of radiation, it actually decreases the amount of radiation that a patient receives in an exam. And by doing that, we often don’t have to scan a patient twice, where previously we may have needed a scan both with and without intravenous contrast. Now we can perform 1 study and have the same amount of information.

Philippa Cheetham, MD: Why is that? Why do you no longer need to give contrast?

Kim L. Sandler, MD: We do have to give contrast, but because of the dual source, we’re actually able to subtract the contrast out. Rather than having to do that non-contrast scan, we can obtain that information even with contrast on board. I think the final thing, and this is very important for lung imaging, is the thin sections. We were originally obtaining images several millimeters wide, but now we’re down to 1 or even smaller than 1-mm thick sections that allow us to see abnormalities that are much smaller.

Philippa Cheetham, MD: When we have imaging that good, is it sometimes too good, such that you image the lungs and see areas that may have been missed on a chest x-ray that either don’t necessarily need treatment or may not be cancers at all? And then you’re left with this dilemma: We see something, but is it something? Is it nothing?

Kim L. Sandler, MD: I think incidental findings are an enormous problem with imaging, and one of the reasons that not everyone should be screened for lung cancer is that you really should have a high risk before you go in to have that study done. The false positive rate has been shown to be so high. Thankfully, we have a lot of work looking at benign findings in CT imaging, so that we can look for patterns—either of calcification or of the way an abnormality may interact with the surface of the lung or with the chest wall—that can indicate to us that it’s something benign and would not necessarily require additional follow-up.

Philippa Cheetham, MD: Do you find it harder to interpret imaging in patients who have been smokers versus those who haven’t?

Kim L. Sandler, MD: When we see patients who are long-time smokers and we see emphysematous changes in their lungs, our suspicion is immediately enhanced that they may have a lung cancer, because we can see all of the other abnormalities. We also know that patients with a certain type of pulmonary fibrosis can be at higher risk. When you have a lot of parenchymal destruction and things like scarring in the lung, it can make interpreting the images that much more difficult. But I think our necessary suspicion has to increase because we know that those patients are at higher risk for having a cancer.

Philippa Cheetham, MD: Now, 20 years ago, radiologists were not looking at so many CTs for screening. The imaging got better. The technologies got better. Do you think that the reporting got better, that you are better able to detect these cancers because you’re seeing more of them and reading more CT scans as a result of this national screening?

Kim L. Sandler, MD: Absolutely. I think that we have had access to so many images and so many different patients, and there are some wonderful researchers who have compiled a lot of these images together. We have guidelines from what’s called the Fleischner Society that tell us what types of nodules should be followed and when they should be followed in patients who don’t have a previous diagnosis of cancer. What we’ve actually seen is that some of those guidelines have become less stringent and we thought that maybe we were imaging patients too often. Maybe we were getting too many scans and we were following a lot of things that turned out to be benign. And because so many radiologists are sharing these images and putting them together and looking at all of these different examples of things that turn into cancer and things that don’t turn into cancer, I think that we can make a better educated guess earlier and do more appropriate follow-up for patients.

Philippa Cheetham, MD: Like almost everything that we do in medicine now, these scans can be transmitted electronically to other radiologists for second opinions, so you can get feedback on what somebody thinks. And it sounds like these criteria for defining lesions are standardized. If somebody is reporting on east coast or west coast, is there some kind of radiology standardization?

Kim L. Sandler, MD: There certainly is. I think that you have to be aware of what particular area of the country you’re practicing in, because you see different abnormalities in the chest depending on what patients have been exposed to. There are different diseases that are really common in the southeast that we’ve been seeing for many, many years. There are disease patterns that are more common in the southwest and in northern parts of the country. So, I think that it’s really helpful to know where your patients have been spending their time, how long they’ve been there, and what sort of abnormalities you may see. I’m incredibly fortunate that there’s usually a room full of radiologists around me to ask for a second opinion. But yes, we share imaging all the time, and there are new publications almost every minute showing different disease patterns and things that we should be aware of. Information and imaging sharing is easier now than it has ever been.

Transcript Edited for Clarity 

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