Clinical evaluation of interstitial lung disease using 18F-FDG PET/CT

<bold>Background:</bold> The presence and activity of interstitial lung diseases (ILDs) have recently been considered when selecting drugs (e.g. anticancer drugs). KL-6 has the highest sensitivity, specificity, and diagnostic accuracy in ILD detection (Ohnishi, H. et al. Am J Respir Crit Care Med 2002; 165:378-81) and is an indicator of ILD activity (Kohno, N. et al. Am Rev Respir Dis 1993; 148:637-42). Besides, ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) is used to track cancer metastasis, and ¹⁸F-FDG uptake is often found in fibrous lesion. However, reports on ILD presence and activity using ¹⁸F-FDG PET/CT are lacking. <bold>Aim:</bold> To evaluate the presence and activity of ILDs using ¹⁸F-FDG PET/CT and serum KL-6 levels <bold>Methods:</bold> We included patients who were diagnosed with ILDs using ¹⁸F-FDG PET/CT and had serum KL-6 levels measured within 30 days before/after ¹⁸F-FDG PET/CT from October 1, 2013 to September 30, 2019 at Kita-harima Medical Center. All lung adenocarcinoma cases with progressive disease were excluded. We used Spearman’s rank tests to determine the correlation between maximum standardized uptake value (SUVmax) of ¹⁸F-PDG PET/CT and serum KL-6 levels. <bold>Results:</bold> We retrospectively analyzed 56 ILD cases in 44 patients (38 males, 6 females; mean age, 74.0 years), namely idiopathic pulmonary fibrosis (32 cases), collagen-vascular disease-associated lung fibrosis (9), radiation pneumonitis (6), cryptogenic organizing pneumonia (3), nonspecific interstitial pneumonia (3), and drug-induced interstitial lung disease (3). SUVmax had a positive correlation with serum KL-6 levels (r=0.401, p=0.003). <bold>Conclusion:</bold> ¹⁸F-FDG PET/CT may be useful in evaluating the presence and activity of ILDs.