super( 18)F-FDG Uptake in Less Affected Lung Field Provides Prognostic Stratification in Patients with Interstitial Lung Disease

This study evaluated the clinical significance of super( 18)F-FDG PET/CT in patients with interstitial lung disease (ILD), by investigating the relationships between super( 18)F-FDG PET/CT parameters and clinical indicators and by evaluating the prognostic implications of super( 18)F-FDG PET/CT results. Methods: Ninety patients (51 men, 39 women; mean age, 55.4 y; age range, 26-78 y) with ILD who underwent super( 18)F-FDG PET/CT were retrospectively analyzed. SUV sub( mean) was defined as the mean SUV of the less-affected lung field, SUV sub( TF) as adjusted SUV sub( mean) using tissue fraction (TF), and CT sub( mean) as the mean attenuation of the corresponding region of interest on high-resolution CT. SUV sub( mean), SUV sub( TF), and CT sub( mean) were compared in the 90 ILD patients and in 15 age- and sex-matched controls. Correlations of SUV sub( max), SUV sub( mean), SUV sub( TF), and CT sub( mean) with clinical indicators, including estimated percentage of forced vital capacity (%FVC), estimated percentage of diffusion capacity of the lungs for carbon monoxide (%DLco), sialylated carbohydrate antigen Krebs von den Lungen-6 (KL-6), surfactant protein D (SP-D), C-reactive protein (CRP), lactate dehydrogenase (LDH), and ILD-sex-age-physiology (GAP) index, were evaluated using the Spearman rank correlation test and the Tukey-Kramer test. A Cox proportional hazards model was used for univariate and multivariate analyses of factors associated with lung transplantation-free survival. Results: SUV sub( mean), SUV sub( TF), and CT sub( mean) were significantly higher in ILD patients than in healthy controls, except for CT sub( mean) in patients with a nonusual interstitial pneumonia pattern. SUV sub( mean) and CT sub( mean) were significantly correlated with %FVC, %DLco, KL-6, and SP-D; SUV sub( TF) was significantly correlated with %DLco, KL-6, SP-D, and LDH; and SUV sub( max) was weakly correlated with KL-6 and CRP. Univariate analysis showed that SUV sub( mean), SUV sub( TF), sex, %FVC, %DLco, KL-6, and ILD-GAP index were significantly prognostic of lung transplantation-free survival; and multivariate analysis showed that SUV sub( mean) and ILD-GAP index were independently prognostic of lung transplantation-free survival. A higher SUV sub( mean) indicated a poorer prognosis, especially in patients with moderate risk based on ILD-GAP index. Conclusion: SUV sub( mean) was significantly but moderately correlated with clinical indicators, providing independen