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SAN ANTONIO -- With two large randomized trials reporting lower mortality in patients screened for lung cancer, it is now clear that low-dose CT screening saves lives.
But the issue of who should and should not be screened is far from settled, and the topic was widely discussed at CHEST 2018, the annual meeting of the American College of Chest Physicians.
On the closing day, in what was billed as "The Smackdown in San Antonio," leading experts in the field debated two key lung cancer screening questions facing clinicians: "Are we ready for risk-based screening?" and "Should we screen patients with comorbidities?"
The National Lung Screening Trial (NLST), which enrolled 53,454 current or former heavy smokers ages 55 to 74, showed a 15% to 20% lower risk of dying from lung cancer for patients who received low-dose CT scanning, compared with those who received x-rays.
And preliminary findings from the European NELSON trial, reported late last month at the World Conference on Lung Cancer in Toronto, showed that low-dose CT scanning was associated with a 26% decrease in mortality among high-risk men and a startling 61% mortality decrease in high-risk women. The trial included 15,792 participants ages 50 to 74; 84% of the participants were men.
CHEST , revised in January of this year, call for screening asymptomatic smokers and former smokers ages 55 to 77 with a 30-pack-year smoking history who either still smoke or quit within the past 15 years.
The guidelines state that screening should not be performed in patients with comorbidities "that adversely influence their ability to tolerate the evaluation of screen-detected findings, or tolerate treatment of an early-stage screen-detected lung cancer, or that substantially limit their life expectancy (strong recommendation, low-quality evidence)."
Lung cancer pulmonologist Gerard Silvestri, MD, of the Medical College of South Carolina in Charleston, took the 'con' side of the debate on screening for comorbidities, noting that while the NLST and now the NELSON trials make a good case for screening relatively healthy smokers and former smokers, the data as a whole present a different picture for people with serious comorbidities -- especially later-stage chronic obstructive pulmonary disease (COPD).
"The 8 million Americans eligible for screening are already different from the NLST participants," Silvestri said. "They are older and they have more comorbidities and they are also likely to have more competing [potential] causes of death."
He noted that while the major harms associated with screening in NLST were low (approximately 3.1 in 1,000 patients), other studies with sicker populations have shown much greater risk of harm. He cited an analysis of 17 studies that found CT lung screening to be associated with a 22.9% increased risk for surgery for benign disease (or 4.5 unneeded surgeries for every 1,000 patients screened).
Surgery-related mortality also was quite low in NLST, Silvestri said, because the participants received video-assisted thoracoscopic (VAT) procedures performed at high-volume centers by highly skilled practitioners.
"That is not where most people are getting their surgeries," he said. "Surgery can actually kill people, and they are most likely to die if they have comorbid disease."
In the case of patients with COPD, Silvestri said it may make sense to screen patients with early-stage disease who do not have other life-threatening conditions. But he argued that the risks outweigh the benefits in patients with GOLD stage 3 or 4 disease.
Defending the practice of screening patients with comorbidities, Frank Detterbeck, MD, of Yale University and Yale Cancer Center opened with a simple argument: "We already are [screening] and we always have. So I think I can probably stop right there."
He continued, however, citing an analysis of NLST findings suggesting that patients with COPD in the study benefited the most from CT scanning.
Detterbeck cited four main questions clinicians need to ask themselves when considering screening patients with comorbidities:
- Are the comorbidities life-limiting?
- Do they limit biopsy options?
- Do they compromise treatment options?
- Does the life expectancy or treatment effectiveness obviate the benefits from screening?
The CHEST guidelines state that the evidence is not strong enough to recommend routine screening of people who do not meet the age and smoking criteria for lung cancer screening, but are considered high-risk based on risk-prediction calculators (weak recommendation, low-quality evidence).
Defending this policy, Peter Mazzone, MD, of the Cleveland Clinic in Ohio, said the NLST findings that women benefit from screening more than men, and that screening has no benefit in those with squamous cell lung cancers suggest that everyone does not benefit equally from screening.
He noted that risk calculator uncertainty remains an issue. In a recent study that compared nine models in two large populations, only 20% of patients were selected by all nine models, and the number of patients selected with a fixed-risk threshold varied threefold among the models.
Arguing in favor of using risk-prediction models to identify high-risk patients, Douglas Arenberg, MD, of the University of Michigan, told the audience that screening should be encouraged in patients whose risk of death from lung cancer is expected to be higher than their risk of death from other causes.
In people who do not meet the guideline criteria for screening, but have other risk factors, he said, that cannot be achieved without an accurate measure of lung cancer risk.
"We need to use the tools that allow us to gauge competing mortality in those at risk for lung cancer," he said.
All four debaters were involved in writing the 2018 updated CHEST lung screening guidelines, leading panel co-moderator Mark J. Rosen, MD, of Mount Sinai Health System in New York City, to comment that the symposium "Smackdown" billing was somewhat misleading.
"This [panel debate] is entirely an artificial construct," he said. "Everyone agrees with everyone else or the real 'Smackdown' would have been in the room where the guidelines happened."