Background: Lung cancer screening may provide a favorable opportunity for a spirometry examination, to diagnose participants with undiagnosed lung function impairments, or to improve targeting of computed tomography (CT) screening intensity in view of expected net benefit.
Methods: Spirometry was performed in the CT screening arm (n=2,029) of the German Lung Cancer Screening Intervention Study (LUSI)-a trial examining the effects of annual CT screening on lung cancer mortality, in 50-69-year-old long-term smokers. Participants were classified as having chronic obstructive pulmonary disease (COPD) [forced expiration in one second (FEV1)/forced vital lung capacity (FVC) <0.7], preserved ratio impaired spirometry (PRISm; FEV1/FVC ≥0.7 and FEV1% predicted <80%), or normal spirometry. Descriptive statistics were used to examine associations of COPD or PRISm with respiratory symptoms, and self-reported medical diagnoses of respiratory and other morbidities. Logistic regression and proportional hazards regression were used to examine associations of COPD and PRISm, as well as their self-reported medical diagnoses, with risks of lung cancer and all-cause mortality.
Results: A total of 1,987 screening arm participants (98%) provided interpretable spirometry measurements; of these, 34.3% had spirometric patterns consistent with either COPD (18.6%) or PRISm (15.7%). Two thirds of participants with COPD or PRISm were asymptomatic, and only 23% reported a previous medical diagnosis concordant with COPD. Participants reporting a diagnosis tended to be more often current and heavier smokers, and more often had respiratory symptoms, cardiovascular comorbidities, or more severe lung function impairments. Independently of smoking history, moderate-to-severe (GOLD 2-4) COPD (OR =2.14; 95% CI: 1.54-2.98), and PRISm (OR =2.68; 95% CI: 1.61-4.40), were associated with increased lung cancer risk. Lung cancer patients with PRISm less frequently had adenocarcinomas, and more often squamous cell or small cell tumors, compared to those with normal spirometry (n=45), and both PRISm and COPD were associated with more advanced lung cancer tumor stage for screen-detected cancers. PRISm and COPD, depending on GOLD stage, were also associated with about 2- to 4-fold increases in risk of overall mortality, which to 87 percent had causes other than lung cancer.
Conclusions: About one third of smokers eligible for lung cancer screening in Germany have COPD or PRISm. As these conditions were associated with detection of lung cancer, spirometry may help identify populations at high risk for death of lung cancer or other causes, and who might particularly benefit from CT screening.
Keywords: Spirometry; chronic obstructive pulmonary disease (COPD); lung cancer screening; mortality; preserved ratio impaired spirometry (PRISm).
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