Interstitial lung abnormalities in a CT lung cancer screening population: prevalence and progression rate

Abstract

Purpose: To determine the prevalence of interstitial lung abnormalities (ILAs) at initial computed tomography (CT) examination and the rate of progression of ILAs on 2-year follow-up CT images in a National Lung Screening Trial population studied at a single site.

Materials and methods: The study was approved by the institutional review board and informed consent was obtained from all participants. Image review for this study was HIPAA compliant. We reviewed the CT images of 884 cigarette smokers who underwent low-dose CT at a single site in the National Lung Screening Trial. CT findings were categorized as having no evidence of ILA, equivocal for ILA, or ILA. We categorized the type of ILA as nonfibrotic (ground-glass opacity, consolidation, mosaic attenuation), or fibrotic (ground glass with reticular pattern, reticular pattern, honeycombing). We evaluated the temporal change of the CT findings (no change, improvement, or progression) of ILA at 2-year follow-up. A χ(2) with Fisher exact test or unpaired t test was used to determine whether smoking parameters were associated with progression of ILA at 2-year follow-up CT.

Results: The prevalence of ILA was 9.7% (86 of 884 participants; 95% confidence interval: 7.9%, 11.9%), with a further 11.5% (102 of 884 participants) who had findings equivocal for ILA. The pattern was fibrotic in 19 (2.1%), nonfibrotic in 52 (5.9%), and mixed fibrotic and nonfibrotic in 15 (1.7%) of the 86 participants with ILA. The percentage of current smokers (P = .001) and mean number of cigarette pack-years (P = .001) were significantly higher in those with ILA than those without. At 2-year follow-up of those with ILA (n = 79), findings of nonfibrotic ILA improved in 49% of cases and progressed in 11%. Fibrotic ILA improved in 0% and progressed in 37% of cases.

Conclusion: ILA is common in cigarette smokers. Nonfibrotic ILA improved in about 50% of cases, and fibrotic ILA progressed in about 37%.

Figures

Figure 1a:

Low-dose chest CT images show GGO in 66-year-old man who is a current smoker with 30 pack-years of cigarette consumption. (a) Initial image at levels of left upper zones shows GGO. (b) Two years later, GGO in left upper lobe is improved on follow-up CT image.

Figure 1b:

Low-dose chest CT images show GGO in 66-year-old man who is a current smoker with 30 pack-years of cigarette consumption. (a) Initial image at levels of left upper zones shows GGO. (b) Two years later, GGO in left upper lobe is improved on follow-up CT image.

Figure 2a:

Low-dose chest CT images show progression of GGO at level of base of right lower lung in 69-year-old male current smoker with 60 pack-years of cigarette consumption. (a) Initial image shows diffuse GGO. (b) Follow-up CT image 2 years later shows increase in GGO.

Figure 2b:

Low-dose chest CT images show progression of GGO at level of base of right lower lung in 69-year-old male current smoker with 60 pack-years of cigarette consumption. (a) Initial image shows diffuse GGO. (b) Follow-up CT image 2 years later shows increase in GGO.

Figure 3a:

Low-dose chest CT images show usual interstitial pneumonia findings in 68-year-old male former smoker with 61.5 pack-years of cigarette consumption. (a) Initial image at levels of lower zones shows reticular pattern, honeycombing, and GGO that involves mainly peripheral lung regions and bases. (b) Follow-up CT image 2 years later shows progression of reticulation and honeycombing in predominantly peripheral and basal distribution.

Figure 3b:

Low-dose chest CT images show usual interstitial pneumonia findings in 68-year-old male former smoker with 61.5 pack-years of cigarette consumption. (a) Initial image at levels of lower zones shows reticular pattern, honeycombing, and GGO that involves mainly peripheral lung regions and bases. (b) Follow-up CT image 2 years later shows progression of reticulation and honeycombing in predominantly peripheral and basal distribution.