Interstitial Lung Abnormality in Asian Population

Abstract

Interstitial lung abnormalities (ILAs) are radiologic abnormalities found incidentally on chest computed tomography (CT) that can be show a wide range of diseases, from subclinical lung fibrosis to early pulmonary fibrosis including definitive usual interstitial pneumonia. To clear up confusion about ILA, the Fleischner society published a position paper on the definition, clinical symptoms, increased mortality, radiologic progression, and management of ILAs based on several Western cohorts and articles. Recently, studies on long-term outcome, risk factors, and quantification of ILA to address the confusion have been published in Asia. The incidence of ILA was 7% to 10% for Westerners, while the prevalence of ILA was about 4% for Asians. ILA is closely related to various respiratory symptoms or increased rate of treatment-related complication in lung cancer. There is little difference between Westerners and Asians regarding the clinical importance of ILA. Although the role of quantitative CT as a screening tool for ILA requires further validation and standardized imaging protocols, using a threshold of 5% in at least one zone demonstrated 67.6% sensitivity, 93.3% specificity, and 90.5% accuracy, and a 1.8% area threshold showed 100% sensitivity and 99% specificity in South Korea. Based on the position paper released by the Fleischner society, I would like to report how much ILA occurs in the Asian population, what the prognosis is, and review what management strategies should be pursued in the future.

Keywords: Idiopathic Pulmonary Fibrosis; Interstitial Lung Abnormalities; Interstitial Lung Disease; Prognosis.

Fig. 1.

Chest computed tomography (CT) findings of interstitial lung abnormality: lower-lung predominant in the craniocaudal plane. This patient is an 81-year-old man who is heavy smoker with 40 pack-years. (A) Initial chest CT (axial plane) shows ground glass opacity with mild reticulation (arrows), traction bronchiolectasis without honeycomb in subpleural area of posterobasal segment on both lower lobes. (B) Initial chest CT (coronal plane) shows diffuse ground glass opacity with mild reticulation in subpleural area of both lungs. (C) The existing ground glass opacity with reticulation in initial chest CT improved significantly in the follow chest CT performed 9 years after smoking cessation, and it remains only in the right lower lobe (arrow).

Fig. 2.

Chest computed tomography (CT) findings of interstitial lung abnormality: upper-lung predominant in the craniocaudal plane. This patient is a 63-year-old man who is heavy smoker with 40 pack-years. (A) Chest CT (axial plane) shows diffuse ground glass opacity with reticulation (arrows) in peripheral area of both upper lobes. (B) Chest CT (coronal plane) shows diffuse ground glass opacity in upper lobe predominant of both lungs.

Fig. 3.

Prognosis after radiation therapy in patients with lung cancer and interstitial lung abnormality on chest computed tomography (CT). This patient is a 79-year-old man who is heavy smoker with 40 pack-years. (A, B) In the initial chest CT, there is a diffuse centrilobular emphysema in both lung, and a 3 cm sized lung cancer (arrows) in the posterobasal segment of left lower lobe (LLL). In addition, there is traction bronchiectasis with reticular opacity (arrow) in right lower lobe and non-emphysematous cyst with traction bronchiectasis (arrow) in LLL. (C, D) Three months later after radiation therapy, primary lung cancer in the LLL (arrow) decreased in size, but extensive acute radiation pneumonia in the left lung (arrow) and local acute radiation pneumonia in the right middle lobe (arrow) occurred.

Fig. 4.

Quantification of interstitial lung abnormality on chest computed tomography (CT). This patient is a 56-yearold man who is heavy current smoker with 35 pack-years. (A) Initial national lung cancer screening low-dose chest CT showed reticular opacity with ground glass opacity (GGO) in the right lower lobe (arrow) and non-emphysematous cyst in the left lower lobe (arrow), which diagnosed interstitial lung abnormalities. (B) Five years later, follow-up chest CT scans revealed no interval change of reticulation (orange) and new focal honeycomb (red) predominantly in subpleural areas of the right lower lobes. Quantification software subclassified the images as fibrotic interstitial lung abnormality, and the mean quantitative interstitial lung abnormality extent was 1%.

Fig. 5.

Quantification of interstitial lung abnormality on chest computed tomography (CT). This patient is a 76-year-old man who is heavy ex-smoker (quit smoking 20 years ago) with 80 pack-years. (A) Initial national lung cancer screening low-dose chest CT showed reticular opacity with ground glass opacity (GGO) in the both lower lobe (arrows), which diagnosed interstitial lung abnormalities. (B) Two years later, follow-up chest CT scans revealed extension of reticulation (orange) in subpleural areas of the both lower lobes. Quantification software subclassified the images as fibrotic interstitial lung abnormality, and the mean quantitative interstitial lung abnormality extent was 2%.

Fig. 6.

A case of interstitial lung abnormality progressing to usual interstitial lung disease. This patient is a 76-yearold man who is heavy current smoker with 40 pack-years. (A, B) Initial chest computed tomography (CT) showed reticular opacity in the right lower lobe and non-emphysematous cyst with honeycombing in the left lower lobe (arrows), which diagnosed fibrotic interstitial lung abnormalities. At this time, lung biopsy was not performed because the patient refused to take an open lung biopsy. (C) Seven years later, follow-up chest CT scans revealed extensive honeycombing in both lower lobes, which was diagnosed as typical usual interstitial pneumonia.

Fig. 7.

A case of progression of non-fibrotic interstitial lung abnormality. This patient is a 70-year-old man who is heavy current smoker with 30 pack-years. (A) Initial national lung cancer screening low-dose chest computed tomography (CT) showed focal reticular opacity with ground glass opacity in the right lower lobe (arrow), which was diagnosed as nonfibrotic interstitial lung abnormalities. (B) Two years later, national lung cancer screening low-dose chest CT showed progression of reticular opacity with ground glass opacity in the right lower lobe (arrow). (C) Four years later, national lung cancer screening low-dose chest CT showed more progression of reticular opacity with lung destruction in right lower lobe (arrow). At this time, open lung biopsy was performed, and pathological findings showed interstitial lung fibrosis superimposed on inflammation without usual interstitial pneumonia findings. (D) Six years later, national lung cancer screening low-dose chest CT showed a non-emphysematous cyst in the right lower lobe (arrow).