In a prospective cohort study reported in Clinical Imaging, researchers in the International Early Lung Cancer Action Program (I-ELCAP) identified emphysema in nearly one-quarter of patients undergoing baseline low-dose computed tomography (CT) screening for lung cancer. Three-quarters of those found to have emphysema had no prior diagnosis of chronic obstructive pulmonary disease (COPD).
The findings indicate that low-dose CT for lung cancer screening provides an opportunity for identification of emphysema and recommendation of smoking cessation.
Study Details
The study involved data from a prospective cohort of 52,726 consecutive individuals aged 40 to 85 years with risk for—but with no symptoms of—lung cancer. Patients underwent baseline low-dose CT lung cancer screening from 2003 to 2016 in the I-ELCAP.
Among the 52,726 participants:
- 55.8% were male
- Average age was 60.3 years (standard deviation [SD] = 8.8 years)
- Average pack-years was 31.2 (SD = 25.3 pack-years)
- 19,697 (37.4%) were current smokers
- 24,428 (48.2%) were former smokers
- 7,601 (14.4%) were never-smokers
- 46,028 (87.3%) reported no prior COPD diagnosis
- 6,698 (12.7%) reported prior COPD diagnosis.
Prevalence of Emphysema
Low-dose CT evidence of emphysema was found in 12,542 participants (23.8%). Of these, 9,595 (76.5%) had no prior COPD diagnosis and 2,947 (23.5%) had a prior COPD diagnosis. Among all those diagnosed with emphysema, 51.0% (n = 6,391) were current smokers, 47.5% (n = 5,961) were former smokers, and 1.5% (n = 190) were never-smokers.
The prevalence of emphysema was 32.5% (n = 6,391 of 19,697) in current smokers, 23.4% (n = 5,961 of 25,428) in former smokers, and 2.5% (n = 190 of 7,601) in never-smokers. Emphysema was mild in 76.5% of participants (n = 7,337) and moderate (n = 1,926; 20.1%) or severe (n = 332; 3.5%) in 23.6% (n = 2,258 of 9,595).
Factors Associated With Prior vs No Prior COPD Diagnosis in Prevalent Emphysema
Differences in demographic and clinical characteristics between the 9,595 participants with emphysema who had no prior COPD diagnosis and the 2,947 participants with prior COPD diagnosis were analyzed. Univariate analysis showed that participants with no prior COPD diagnosis were significantly more likely to have the following characteristics:
- Male sex
- Younger age
- Completion of ≥ 4 years of college
- Current smoker status
- Fewer pack-years of smoking
- Lower prevalence of history of lung cancer in first-degree relatives
- Fewer self-reported comorbidities of cardiac disease, hypertension, and diabetes.
Those with no prior COPD diagnosis were less likely to have moderate-to-severe emphysema (23.5% vs 42.0%, P < .0001) and high (4–12) ordinal coronary artery classification (CAC) score (23.8% vs 31.1%, P < .0001).
On multivariate analysis, race, smoking status, and CAC score were no longer significantly associated with prior vs no prior COPD diagnosis among participants with emphysema on low-dose CT. Significant independent predictors of no prior COPD diagnosis consisted of:
- Male sex (odds ratio [OR] = 1.47, 95% confidence interval [CI] =1.22–1.44)
- Completion of college education (OR= 1.54, 95% CI = 1.31–1.81)
- Younger age (OR for each 10 years = 0.72, 95% CI = 0.68–0.77)
- Lower pack-years of smoking (OR for each 10 pack-years = 0.90, 95% CI = 0.88–0.92)
- No history of lung cancer in first-degree relatives (OR = 1.12, 95% CI = 1.01–1.24)
- No self-reported cardiac disease (OR = 0.76, 95% CI = 0.65–0.88) or hypertension (OR = 0.74, 95% CI = 0.67–0.81)
- Less severe emphysema on low-dose CT (ORs = 0.58, 95% CI = 0.52–0.64 for moderate and 0.23, 95% CI = 0.19–0.27 for severe).
For participants without vs with prior COPD diagnosis, emphysema was moderate in 20.1% vs 28.9% (P = .0007) and severe in 3.5% vs. 13.1% (P < .0001).
Among participants with emphysema on low-dose CT, the prevalence of lung cancer detected on imaging was 2.6% among those with no prior COPD diagnosis vs 3.1% among those with prior diagnosis (P = .12).
The investigators concluded, “Emphysema was identified in 23.8% participants undergoing low-dose CT and was unsuspected in 76.5%. Low-dose CT provides an opportunity to identify emphysema and recommend smoking cessation.”
Claudia I. Henschke, PhD, MD, of the Department of Radiology, Mount Sinai School of Medicine, is the corresponding author for the Clinical Imaging article.
Disclosure: The study was funded in part by the Flight Attendant Medical Research Institute. For full disclosures of the study authors, visit clinicalimaging.org.
