SUVmean of background lung in FDG-PET/CT provides clinical information and prognostic stratification in interstitial lung disease

Objectives It is known that 18F-fluorodeoxyglucose (FDG) is taken up by inflammatory cells. The purpose of this study was to investigate whether positron emission tomography (PET) / computed tomography (CT) with FDG provided prognostic information in interstitial lung disease (ILD).

Methods Ninety patients (male:female=51:39; mean age, 55.4 years; range, 26 - 78 years) with ILD who underwent PET scan at single institute were retrospectively analysed. First, mean standardized uptake value (SUVmean) in background lung field was compared between ILD patients and 15 patients without ILD. Then, correlations between SUVmean and several clinical indicators (%FVC, %DLco, KL-6, SP-D, CRP, LDH, and ILD-GAP index) were evaluated using Spearman’s rank correlation test and Tukey-Kramer test. Finally, univariate and multivariate analyses were performed for factors predictive of transplantation free survival using Cox proportional hazard model.

Results The SUVmean was significantly higher in ILD patients than in controls (0.64 ± 0.24 vs. 0.41 ± 0.062, p < 0.0001), and had moderate, but significant correlation with %FVC (ρ = -0.45, p < 0.0001), %DLco (ρ = -0.46, p = 0.0002), KL-6 (ρ = 0.56, p < 0.0001), and SP-D (ρ = 0.36, p = 0.0098). In univariate analysis, SUVmean, gender, %FVC, %DLco, KL-6, and ILD-GAP index were significant prognostic factors. In multivariate analysis, SUVmean was an independent prognostic factor when adjusted by ILD-GAP index, i.e. higher SUVmean ( > 0.62) indicated poor prognosis in patients with moderate risk.

Conclusions FDG uptake in background lung field had moderate correlation with clinical indicators, and provided prognostic information in ILD with moderate risk. FDG-PET/CT might be helpful for risk stratification of ILD patients.

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