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 (SUVmean , SUVmax , respectively) were measured in the fibrotic area. Adjusted SUV, including SUV ratio (SUVR, defined as SUVmax -to-liver SUVmean ratio), tissue fraction-corrected SUVmean (SUVmeanTF ), and SUVR (SUVRTF ), and tissue-to-blood ratio (SUVmax /SUVmean venous; TBRblood ) 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 SUVmean , SUVmax , and SUVmeanTF 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), SUVRTF (HR, 1.441; 95% CI, 1.000-2.098), and TBRblood (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.