The Value of (18)F-FDG PET/CT in Evaluating Disease Severity and Prognosis in Idiopathic Pulmonary Fibrosis Patients

BACKGROUND: Several parameters are useful for assessing disease severity in idiopathic pulmonary fibrosis (IPF); however, the role of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) is not well-defined. We aimed to evaluate the value of (18)F-FDG PET/CT for assessing disease severity and prognosis in IPF patients. METHODS: Clinical data of 89 IPF patients (mean age: 68.1 years, male: 94%) who underwent (18)F-FDG PET/CT for evaluation of lung nodules or cancer staging were retrospectively reviewed. Mean and maximal standardized uptake values (SUV(mean), SUV(max), respectively) were measured in the fibrotic area. Adjusted SUV, including SUV ratio (SUVR, defined as SUV(max)-to-liver SUV(mean) ratio), tissue fraction-corrected SUV(mean) (SUV(meanTF)), and SUVR (SUVR(TF)), and tissue-to-blood ratio (SUV(max)/SUV(mean) venous; TBR(blood)) were obtained. Death was defined as the primary outcome, and associations between other clinical parameters (lung function, exercise capacity, C-reactive protein [CRP] level) were also investigated. RESULTS: All SUV parameters were inversely correlated with the forced vital capacity, diffusing capacity for carbon monoxide, and positively correlated with CRP level and the gender-age-physiology index. The SUV(mean), SUV(max), and SUV(meanTF) were associated with changes in lung function at six months. The SUVR (hazard ratio [HR], 1.738; 95% confidence interval [CI], 1.011–2.991), SUVR(TF) (HR, 1.441; 95% CI, 1.000–2.098), and TBR(blood) (HR, 1.377; 95% CI, 1.038–1.827) were significant predictors for mortality in patients with IPF in the univariate analysis, but not in the multivariate analysis. CONCLUSION: (18)F-FDG PET/CT may provide additional information on the disease severity and prognosis in IPF patients, and the SUVR may be superior to other SUV parameters.