Evidence of interstitial lung disease on low-dose chest CT images: Prevalence, patterns, and progression

OBJECTIVE. The purposes of this study were to determine the prevalence of interstitial lung disease (ILD) in a cohort undergoing low-dose CT screening for lung cancer, to identify the CT patterns of fibrosis, and to determine prognostic factors of disease progression. MATERIALS AND METHODS. The study drew from a database of 951 participants in a lung cancer screening program between 2010 and 2014. Three thoracic radiologists reviewed CT scans to identify the ILD findings, defined as traction bronchiectasis, ground-glass opacities with traction bronchiectasis, reticulations with traction bronchiectasis, and honeycombing. Evidence of ILD was considered present if at least two of three reviewing radiologists agreed. Age, smoking history, and CT evidence of emphysema were also documented. RESULTS. Of the 951 participants, 63 (6.6%) had CT evidence of ILD, and 16 of the 63 (1.7% of the total cohort) had honeycombing. Significant univariate predictors of ILD were male sex (p = 0.003), older age (p < 0.0001), higher number of pack-years of cigarette smoking (p = 0.0003), and greater severity of emphysema (p = 0.004), but only age and male sex remained significant in the multivariate analysis. The most common pattern of ILD was peripheral fibrosis without honeycombing involving multiple lobes. The presence of honeycombing was significantly associated with progression of fibrosis score (p = 0.0001) and extent of fibrosis (p = 0.005). CONCLUSION. A potential added benefit of CT screening is earlier diagnosis of ILD in older smokers, who are at increased risk. Radiologists should recognize the earliest findings of ILD and understand the importance of early recognition.