Interstitial lung abnormalities in the Queensland Lung Cancer Screening Study: prevalence and progression over 2 years of surveillance

Abstract

Background We report the prevalence and progression of incidentally detected interstitial lung abnormalities (ILA) in the Queensland Lung Cancer Screening Study cohort. Methods About 256 volunteers aged 60–74, with ≥30 pack years smoking history and forced expiratory volume in 1 s (FEV1) ≥50% predicted underwent low‐dose computed tomography (CT) chest screening. Electronic search of baseline (T0) and 2‐year follow‐up (T2) CT reports identified candidate cases using Fleischner Society interstitial terminology. Candidate CT were reviewed in a randomised order by two experienced radiologists and a senior respiratory medicine trainee blinded to the existing reports. Scans were evaluated for the presence and extent of ILA using an in‐house score, and graded for progression. Results ILA were detected in 20/256 baseline cases (7.8%) with no incident cases detected at T2 surveillance imaging. Of these 20 cases, 9 (45%) had reticulation, 18 (90%) had ground glass change, 1 had traction bronchiectasis and 1 had randomly distributed nodularity. Seven cases with ground glass changes also had areas of reticulation, and only two had reticulation alone. All ILA were graded as minor except for traction bronchiectasis, which was moderate. Only one case progressed on T2 imaging. ILA were associated with the presence of auscultatory crackles (50% vs 11.6%, P = 0.001) and a lesser degree of emphysema (mean % volumetric emphysema 6.7% vs 9.8%, P = 0.009). No relationship was observed between baseline and serial lung function parameters. Conclusion ILA are frequent incidental findings in lung cancer screening. In the majority of cases these abnormalities do not appear to change significantly over a 2‐year period of surveillance.

Low dose CT detected interstitial lung abnormalities in a population with low asbestos exposure

“…The prevalence of ILA in the present study is higher than other nonoccupational LDCT studies with reports ranging between 2.1% and 16.7% 41,44–48 and in LDCT studies of occupational (including asbestos) exposed populations the prevalence of ILA ranges from 0.7% to 25% 17,18 . Comparisons with other cohorts should be with care as standardized methods or criteria for describing ILA/ILD in CT populations have not been defined 49 .…”

“…This is defined as specific radiologic, physiological, and histopathologic abnormalities in asymptomatic individuals or individual with ILA on CT imaging, which are usually more subtle than those of individuals with established disease 39 . The increasing use of chest CT both in clinical and research settings has increased the detection of subclinical ILD and the long‐term clinical significance of ILAs remain unclear 37–41 . Only a very small proportion (1.8%) in the present study of those with ILA fitted the accepted definition of declining pulmonary function in the context of ILD 14,36 and therefore there appears to be little role for antifibrotic therapy in this population.…”

Interstitial lung abnormalities – current knowledge and future directions

“…In general population-based cohorts in which the mean age of participants with ILA was 70 years or older, the prevalence of ILA has been reported between 7 and 10% [ 8 , 16 , 17 ]. Among cohorts of smokers or lung cancer screening cohorts, however, the prevalence of ILA has been found to range from 4 to 20% [ 5 , 8 , 14 , 15 , 18–20 ]. While these numbers are similar to prevalence rates in the general population-based cohorts it should be noted that the mean age of participants with ILA in the cohorts of smokers ranged from 60 to 66 years, approximately 10 years younger than in the general population-based cohorts.…”

“…Progression of ILA has been noted in 73–76% of participants with ILA over 5 years of follow up [ 50 , 74 ]. Still, studies with a follow up of 2 years, albeit with younger participants and a slightly differing definition of ILA, have found that a much lower proportion of participants progress over that time [ 14 , 18 ]. Progression to ILD has been found to be common among relatives of familial interstitial pneumonia patients with ILA [ 40 ].…”

Increased respiratory morbidity in individuals with interstitial lung abnormalities

“…Interstitial lung abnormalities (ILA) are a group of radiological findings visible on computed tomography (CT) of the lung in individuals without a diagnosis of interstitial lung disease (ILD) [1]. They are common in participants of lung cancer screening trials, patients with chronic obstructive pulmonary disease (COPD) and broad population-based cohorts [2][3][4][5][6][7][8]. Similar radiologic findings (nodular changes, reticulation, ground glass opacities and honeycombing) are also present in several interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF), and can precede onset of disease symptoms and diagnosis by several years [1,9,10].…”