Carla Lamb, MD: Innovations in CT Scan Accuracy

On the latest episode of Lungcast, American Lung Association (ALA) chief medical officer Albert Rizzo, MD, discussed the young history and recent breakthroughs of interventional pulmonology medicine with field innovator Carla Lamb, MD, director of interventional pulmonary medicine and the relevant pulmonary fellowship program at Lahey Hospital & Medical Center.

During the interview, discussion turned to the utility of low-dose CT screening for lung cancer in the US, and the emerging techniques and materials becoming available for frontline clinicians. Watch the clip above to hear the full segment conversation.

Lungcast is a monthly respiratory health podcast series from the ALA produced by HCPLive.

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Rizzo: One of the reasons cited for some of the slow uptake of CT screening nationally—which I think stands around 6% over the last 10 years since the NSLP—even though it showed 20% mortality benefit, there's been concern over false positives and the subsequent potential complications of unwarranted procedures.

Now, what are some of the evolving interventional pulmonology techniques and devices that are available to help make the approach to low-dose CT screening for lung cancer less likely to lead to unwarranted surgeries or complications from potentially benign disease?

Lamb: So I would start off with a couple of things. Now, we know that since March of 2021, there's been an adaption to broadening the inclusion criteria for lung screening. So before, there were about 9 million patients eligible for screening. Now, we've nearly doubled that to nearly 18 million eligible patients for screening. We have a lot of work to do for screening Massachusetts. It's actually one of the leading states for screening, but we have a lot of work yet to do also.

What I would remind the listeners about inclusion is that right now, the new criteria is age 50 to 80 years, at least a 20-pack year tobacco history, and there's some evolution about the timing of quit—15 years of quitting. We believe that going forward in the future, we will see a dropping off of that need and patients will be eligible for longer screening beyond the 15-year quit rate, because we know that patients continue to age into lung cancer far beyond their smoking cessation days. That's a work in progress but for now, the criteria has opened up the door for more people to be screened.

Now getting back to the coating of the false positive rate. I would say unfortunately, even in the published literature, it's misquoted. And so hopefully this will give me an opportunity to clarify that. You know, when we think about the original NLST, you have to remember the size of the nodule that they deem positive was a smaller nodule size at 4 millimeters. Over evolution of Lung Rads, one of the standardized, validated reporting systems—that evolved, and this was supported and endorsed by the American College of Radiology—is that the nodule size is now really 6 millimeter and beyond. So, with the change in the size of what defines a positive, the false positive rate invariably went down just based on that definition alone, number one. And then if a patient begins with their first lung screening scan, but they remain in the program on 1 and 2 consecutive screening scans, the false positive rate potential in that patient markedly declines from what was previously quoted as high as 26% now to really 7%, and sometimes even lower. So I would want to stress that point that the false positive rate is far, far lower now with the evolution of what's defined as a positive in the first place.

And number two, patients who maintain continuation in a lung screening program beyond their first scan, it markedly drops that false positive for each respective patient, less than 7%. So I think that's a very important point. But I do think it also still requires us to be very responsible in how we discuss with the patient the finding.

In the majority of patients who have a lung screening scan, they'll have a normal scan or a non-actionable scan, meaning no abnormal finding requiring an intervention. But I think this is where by having a multidisciplinary group of experts who are looking and guiding, in addition to the Lung Rads recommendation, to responsibly manage those patients who clearly do need further activation of a pathway of diagnostic evaluation to those who can safely and responsibly be followed with just serial CT scans based on the guidelines and the recommendation of Lung Rads.

Now, in the interventional field, how do we come into play? Well, I think for those patients who do have a nodule that is more suspect based on Lung Rads, and being in the high-risk category, I think we look at those patients and say, 'How can we minimally invasively define what that nodule is beyond the scan?' And so the evolution of interventional really incorporates several things; now there are auto-antibody measurements that can be done in the serum in the blood. There are now through registries, our nasal brushings look at messenger RNA epithelial injury patterns, to further risk-stratify a nodule beyond a CT scan—and even beyond a PET or in conjunction with those. There are endobronchial brushings that can also pick up an mRNA epithelial injury pattern that may translate from the nasal mucosa to the bronchial mucosa to that distal, more peripheral nodule. So those are some things that can be integrated as part of the workup.

But more specific to interventional, now the evolution has gone from basic bronchoscopy to radial probe EBUS, to reach out in the periphery, to identify that you are at your target before you take your biopsy, to electromagnetic navigation tools and catheters. And now, most recently, over the last several years, at least 2 approved platforms: a robotic bronchoscopy—and what they do is they extend the reach on those small nodules that are deemed to be worthy of a biopsy. The beauty of a robotic bronchoscopy and a bronchoscopic inspection to those nodules is that we can look at the mediastinum with linear EBUS and assess that. We go to the peripheral nodule with the robotic tool. It's a much smaller catheter. It has dexterity beyond anything that's out there. It's kind of the newest iteration of making us the most dexterous and the most peripheral spaces to get the smallest nodules that were deemed in the past not attainable by bronchoscopy.

So that's probably the most groundbreaking evolution that we're currently putting into practice at the bedside currently, and the goal and hope is that we can evolve into—and trials are currently actively being done—delivery of therapeutic medications or thermal therapies to ablate cancerous nodules that are singular nodules that can be treated in a minimally invasive and even a non-surgical way. So that's that's in the future, but rapidly being evaluated and tested.