18F-FDG Uptake in Less Affected Lung Field Provides Prognostic Stratification in Patients with Interstitial Lung...

This study evaluated the clinical significance of ¹⁸F-FDG PET/CT in patients with interstitial lung disease (ILD), by investigating the relationships between ¹⁸F-FDG PET/CT parameters and clinical indicators and by evaluating the prognostic implications of ¹⁸F-FDG PET/CT results.

Ninety patients (51 men, 39 women; mean age, 55.4 y; age range, 26-78 y) with ILD who underwent ¹⁸F-FDG PET/CT were retrospectively analyzed. SUV_mean was defined as the mean SUV of the less-affected lung field, SUV_TF as adjusted SUV_mean using tissue fraction (TF), and CT_mean as the mean attenuation of the corresponding region of interest on high-resolution CT. SUV_mean, SUV_TF, and CT_mean were compared in the 90 ILD patients and in 15 age- and sex-matched controls. Correlations of SUV_max, SUV_mean, SUV_TF, and CT_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.

SUV_mean, SUV_TF, and CT_mean were significantly higher in ILD patients than in healthy controls, except for CT_mean in patients with a nonusual interstitial pneumonia pattern. SUV_mean and CT_mean were significantly correlated with %FVC, %DLco, KL-6, and SP-D; SUV_TF was significantly correlated with %DLco, KL-6, SP-D, and LDH; and SUV_max was weakly correlated with KL-6 and CRP. Univariate analysis showed that SUV_mean, SUV_TF, sex, %FVC, %DLco, KL-6, and ILD-GAP index were significantly prognostic of lung transplantation-free survival; and multivariate analysis showed that SUV_mean and ILD-GAP index were independently prognostic of lung transplantation-free survival. A higher SUV_mean indicated a poorer prognosis, especially in patients with moderate risk based on ILD-GAP index.

SUV_mean was significantly but moderately correlated with clinical indicators, providing independent prognostic information in patients with ILD. ¹⁸F-FDG PET/CT may be helpful for monitoring and risk stratification of ILD patients.