Abstract
IntroductionTo investigate the combined performance of quantitative CT (qCT) following a computer algorithm analysis (IMBIO) and 18F-FDG PET/CT to assess survival in patients with idiopathic pulmonary fibrosis (IPF).MethodsA total of 113 IPF patients (age 70 ± 9 years) prospectively and consecutively underwent 18F-FDG PET/CT and high-resolution CT (HRCT) at our institution. During a mean follow-up of 29.6 ± 26 months, 44 (48%) patients died. As part of the qCT analysis, pattern evaluation of HRCT (using IMBIO software) included the total extent (percentage) of the following features: normal-appearing lung, hyperlucent lung, parenchymal damage (comprising ground-glass opacification, reticular pattern and honeycombing), and the pulmonary vessels. The maximum (SUVmax) and minimum (SUVmin) standardized uptake value (SUV) for 18F-FDG uptake in the lungs, and the target-to-background (SUVmax/SUVmin) ratio (TBR) were quantified using routine region-of-interest (ROI) analysis. Pulmonary functional tests (PFTs) were acquired within 14 days of the PET/CT/HRCT scan. Kaplan–Meier (KM) survival analysis was used to identify associations with mortality.ResultsData from 91 patients were available for comparative analysis. The average ± SD GAP [gender, age, physiology] score was 4.2 ± 1.7 (range 0–8). The average ± SD SUVmax, SUVmin, and TBR were 3.4 ± 1.4, 0.7 ± 0.2, and 5.6 ± 2.8, respectively. In all patients, qCT analysis demonstrated a predominantly reticular lung pattern (14.9 ± 12.4%). KM analysis showed that TBR (p = 0.018) and parenchymal damage assessed by qCT (p = 0.0002) were the best predictors of survival. Adding TBR and qCT to the GAP score significantly increased the ability to differentiate between high and low risk (p < 0.0001).Conclusion18F-FDG PET and qCT are independent and synergistic in predicting mortality in patients with IPF.
Highlights
To investigate the combined performance of quantitative CT following a computer algorithm analysis (IMBIO) and 18F-FDG Positron emission tomography (PET)/CT to assess survival in patients with idiopathic pulmonary fibrosis (IPF)
PET studies in animals have yielded potentially valuable insight into the biology of IPF, with heightened 18Ffluorodeoxyglucose (18F-FDG) PET signal intensity related to interstitial lung changes [5, 6]. 18F-FDG pulmonary uptake on PET has been shown to relate to disease severity as assessed by quality-of-life measurement, lung volume, and gas transfer, and more recently it was shown that baseline objective measures of 18F-FDG uptake on PET predict patient survival, independent of pulmonary function tests (PFTs) [7, 8]
We propose to add to the GAP index another factor based on the best predictor for PET according to the prognostic ability of the biomarker to create a synthetic score based on the imaging test as previously described [8]
Summary
To investigate the combined performance of quantitative CT (qCT) following a computer algorithm analysis (IMBIO) and 18F-FDG PET/CT to assess survival in patients with idiopathic pulmonary fibrosis (IPF). KM analysis showed that TBR (p = 0.018) and parenchymal damage assessed by qCT (p = 0.0002) were the best predictors of survival. High-resolution CT (HRCT) is the current imaging reference standard in the investigation of patients with idiopathic pulmonary fibrosis (IPF), revealing structural details of the entire lung parenchyma which reflect the characteristic histological changes. 18F-FDG pulmonary uptake on PET has been shown to relate to disease severity as assessed by quality-of-life measurement, lung volume, and gas transfer, and more recently it was shown that baseline objective measures of 18F-FDG uptake on PET predict patient survival, independent of PFTs [7, 8] PET studies in animals have yielded potentially valuable insight into the biology of IPF, with heightened 18Ffluorodeoxyglucose (18F-FDG) PET signal intensity related to interstitial lung changes [5, 6]. 18F-FDG pulmonary uptake on PET has been shown to relate to disease severity as assessed by quality-of-life measurement, lung volume, and gas transfer, and more recently it was shown that baseline objective measures of 18F-FDG uptake on PET predict patient survival, independent of PFTs [7, 8]
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