Emphysema Evidence on CT Can Predict Disease Progression in Smokers

The presence of visual parenchymal emphysema caught on CT can be used to predict how the condition will progress in both current and former smokers, even among those who are in the early stages of chronic obstructive pulmonary disease (COPD), according to new research.

More and more often, CT is being used to evaluate patients with COPD in an effort to determine whether a patient has emphysema, and if so what pattern it follows and how severe it is. Those images can also quantify additional COPD features, including air trapping and airway abnormality.

But, a team of investigators from Hôpital Erasme at the Université Libre de Bruxelles wanted to know whether the visual severity of emphysema was connected to any subsequent progression of the disease. They published their findings on Dec. 15 in Radiology.

“The presence of visible parenchymal or paraseptal emphysema at CT in current or former smokers is an important predictor of subsequent progression of emphysema,” said the team led by Bilal El Kaddouri, M.D. “[Our results] suggest visual emphysema behaves as an independent and sensitive parameter to predict changes, even in those with early stages of COPD.”

Their findings show that the presence of visual emphysema on CT at baseline is associated with disease progression and air trapping compared to those without signs of the condition, and that progression appears more often in African American patients than in their white counterparts.

“Our finding supports the increasing awareness that symptoms and progressive structural abnormalities are common in individuals with and without COPD,” the team said. “An important implication is that trials of emphysema treatment could be enriched by selective inclusion of patients with visual emphysema at CT.”

Axial CT images show major elements of Fleischner Society scoring system for parenchymal emphysema. (a) Mild centrilobular emphysema (involving less than 5% of lung lobe). (b) Moderate centrilobular emphysema (involving more than 5% of lung zone). (c) Confluent emphysema. (d) Advanced destructive emphysema. Courtesy: RSNA

Kaddouri’s team pulled 4,166 current and former smokers with at least a 10-pack-years of exposure who either did or did not have COPD from the Genetic Epidemiology of COPD (COPDGene) Study to learn more from visual emphysema. The selected patient group included both African American and white patients.

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Initially, the team assessed their Fleischner Society visual CT scores at baseline, quantitative inspiratory, and expiratory CT. They repeated these scans after five years. Patients also underwent pulmonary function testing at baseline CT and after five years. Overall, study participants were classified based on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification system.

Based on their analysis, patients who showed signs of visual emphysema did experience different outcomes. Within the patient group, 61 percent – 2,525 patients – initially presented with trace centrilobular emphysema (CLE) pattern, and 42 percent – 1,737 individuals – showed the paraseptal emphysema (PSE) pattern.

For patients in both groups, severe emphysema was associated with more frequent exacerbations in the year prior to the study enrollment, the team said, and those patients also had increased GOLD stage, airflow obstruction worsening, and they walked shorter distances during the 6-minute walk test. The team also determined that the visual emphysema patterns matched well with emphysema quantitation.

For patients with the CLE pattern, 63 percent were graded as trace or mild, and the remaining patients were graded as moderate-to-advanced destructive. Kaddouri’s team determined that increased CLE severity coincided with older age, lower weight, and being white. Additionally, higher-grade emphysema also appeared in patients who had the greatest smoking histories – from 40 pack-years to 58 pack-years.

Axial CT images show major elements of Fleischner Society scoring system for parenchymal emphysema. (a) Mild centrilobular emphysema (involving less than 5% of lung lobe). (b) Moderate centrilobular emphysema (involving more than 5% of lung zone). (c) Confluent emphysema. (d) Advanced destructive emphysema. Courtesy: RSNA

Outcomes were somewhat similar for patients with the PSE pattern. Of the group, 58 percent were graded as mild, and 42 percent were graded as substantial. Based on the analysis, visual PSE was related to a lower proportion of white participants and more persistent current smokers with higher smoking histories.

In addition, the team found that patients who had COPD with a visual presence of mild, moderate, and confluent emphysema at baseline CT also showed an average decline in lung density of 4.6 g/L +/- 1.1, 6.7 g/L +/- 1.1, and 6.4 g/L +/1 1.2, respectively. In contrast, patients with trace evidence experienced a drop of 2.4 g/L +/- 1.3. Lung density declines did not reach the same level among study participants who did not have COPD. For those with mild or moderate emphysema at CT baseline, the average drop was 3.6 g/L +/- 1.0 and 3.1 g/L +/- 1.6, respectively, and it was 1.8 g/L +/- 1.0 for patients with trace emphysema.

The most noticeable difference with lung density, the team said, was based on race. African American patients with COPD and visual emphysema saw an average decline of 6.7 g/L compared to 4.6 g/L for white patients.

These findings show that smokers who have visible parenchymal emphysema at CT did show progression of the condition at five years when patients without visual evidence did not, the team said. Their study also expands the existing body of information because it includes patients with COPD who were stratified according to GOLD groups. The five-point grading of parenchymal emphysema is associated with subsequent disease progression independent of baseline GOLD stage, suggesting that visual emphysema can be an independent and sensitive parameter to predict changes.

Ultimately, the team concluded, these results could have a clinical impact with this patient population.

“The presence of visible parenchymal or paraseptal emphysema at CT in current or former smokers is an important predictor of subsequent progression of emphysema,” the team said. “The Fleischner Society emphysema grading system may be useful as a simple prognostic marker in smokers, with or without chronic obstructive pulmonary disease and may have value in therapeutic trials and in clinical practice.”

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