18F-FDG Accumulation in Less-Affected Lung Area Predicts Postoperative Interstitial Lung Disease Acute Exacerbation in Lung Cancer: A Case Control Study

Background: Pneumonectomy for lung cancer with interstitial lung disease (ILD) has been shown to cause postoperative acute exacerbation (AE) of the ILD. The accumulation of 18F-flurodeoxyglucose (FDG) on normal parenchymal or less-affected lung fields in 18F-FDG-positron emission tomography (PET)/computed tomography (CT) has been reported to be related to ILD disease activity and prognosis. To determine whether 18F-FDG accumulation in normal parenchymal or less-affected lung fields on 18F-FDG-PET/CT can predict postoperative AE of ILD in non-small cell lung cancer (NSCLC) patients with ILD.Methods: This retrospective study included 36 NSCLC patients with ILD, who underwent 18F-FDG-PET/CT at 2 institutions before pulmonary surgery. A single volume-of-interest (VOI) was placed to measure the mean standardized uptake value (SUVmean) in normal or less-affected lung fields at 12 areas on the ventral and dorsal locations of both lungs, in each level of the aortic arch, tracheal bifurcation, and the orifice of the right lower pulmonary vein into the left atrium. The region to which the target VOI was set corresponded to no or minimally increased attenuation on high resolution CT. The SUVmean was defined as the mean SUV of the target VOI, SUVtissue fraction (TF) as the corrected SUVmean by using TF and mean computed tomography density (CTDmean) as the mean attenuation of the corresponding target VOI on HRCT. We performed a phantom study to optimize SUV difference among 2 institutions. The corrected SUVmean (cSUVmean) and corrected SUVTF (cSUVTF) were calculated based on the phantom study result.Results: Among 36 NSCLC patients with ILD who underwent pulmonary surgery, 8 patients developed postoperative AE of ILD. The cSUVmean values in the ventral and dorsal locations at the aortic arch level, and in the ventral location at the tracheal bifurcation level in the group with postoperative AE were higher than in the group without postoperative AE. There was no significant difference in the value of cSUVTF and CTDmean between the groups with and without postoperative AE.Conclusion: 18F-FDG accumulation in the normal or less-affected lung fields can potentially predict postoperative AE of ILD in NSCLC patients with ILD.