In a prospective cohort study reported in Clinical Imaging, David Steiger, MD, of the Division of Pulmonary, Critical Care and Sleep Medicine, Icahn School of Medicine at Mount Sinai, in New York, and colleagues 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.1 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.
David Steiger, MD
As noted by the investigators: “…COPD includes chronic bronchitis, small airways disease, and emphysema. Diagnosis of COPD requires spirometric evidence and may be normal even when small airways disease or emphysema is present. Emphysema increases the risk of exacerbations and is associated with all-cause mortality and increased risk of lung cancer. We evaluated the prevalence of emphysema in participants with and without a prior history of COPD.”
The study involved data from a prospective cohort of 52,726 consecutive individuals aged 40 to 85 years at risk for but with no symptoms of lung cancer who 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), and average pack-years was 31.2 (SD = 25.3 pack-years). Overall, 19,697 (37.4%) were current smokers, 24,428 (48.2%) were former smokers, and 7,601 (14.4%) were never-smokers. In addition, 46,028 (87.3%) reported no prior COPD diagnosis and 6,698 (12.7%) reported a prior COPD diagnosis.
Prevalence of Emphysema
Low-dose CT evidence of emphysema was found in 12,542 participants (23.8%). Of these individuals, 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 = 6,391/19,697) in current smokers, 23.4% (n = 5,961/25,428) in former smokers, and 2.5% (n = 190/7,601) 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 = 2,258/9,595).
Factors Associated With Prior vs No Prior COPD Diagnosis in Prevalent Emphysema
Differences in demographic and clinical characteristic between the 9,595 participants with emphysema who had no prior COPD diagnosis and the 2,947 participants with a prior COPD diagnosis were analyzed.
Univariate analysis showed that participants with no prior COPD diagnosis were more likely to have the following characteristics: male sex (P < .0001); younger age (62.1 vs 65.1 years, P < .0001); completion of at least 4 years of college (34.4% vs 27.1%, P < .0001); current smoker status (51.9% vs 47.8%, P = .03); fewer pack-years of smoking (42.3 vs. 51.4 pack-years, P < .0001); lower prevalence of history of lung cancer in first-degree relatives (20.4% vs 22.2%, P = .02); and fewer self-reported comorbidities of cardiac disease (7.9% vs 11.7%, P < .0001), hypertension (24.8% vs 32.1%, P < .0001), and diabetes (8.7% vs 10.8%, P = .0008). 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), and 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 a 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 low-dose CT was 2.6% among those with no prior COPD diagnosis vs 3.1% among those with a prior COPD diagnosis (P = .12).
The investigators concluded: “In our study of 52,726 consecutive asymptomatic patients who underwent [low-dose CT] screening for lung cancer, 23.8% (n = 12,542) had evidence of emphysema. Among the 12,542, 76.5% (n = 9,595) reported no prior diagnosis of COPD. Among the 9,595, 2,258 [23.6%] had moderate or severe emphysema. Our findings further support the observation that COPD may be underdiagnosed, even when there is advanced emphysema. [Low-dose CT] may facilitate the diagnosis of emphysema, which is associated with an increase in morbidity and deaths due to lung cancer and other causes. The diagnosis provides opportunities to initiate smoking cessation and pharmacotherapy for COPD and can direct the clinician to look for important, treatable conditions that coexist in patients with COPD.”
DISCLOSURE: The study was funded in part by the Flight Attendant Medical Research Institute. Dr. Steiger has been employed by Freenome and holds stock or other ownership interests in Xyphos.
1. Steiger D, Siddiqi MF, Yip R, et al: The importance of low-dose CT screening to identify emphysema in asymptomatic participants with and without a prior diagnosis of COPD. Clin Imaging 78:136-141, 2021.