18F-Fluorodeoxyglucose positron emission tomography may not visualize radiation pneumonitis

Abstract

BackgroundRadiation pneumonitis is a common and potentially fatal complication of radiotherapy (RT). Some patients with radiation pneumonitis show increases in uptake of fluorodeoxyglucose (FDG) on positron emission tomography (PET), but others do not. The exact relationship between radiation pneumonitis and 18F-FDG PET findings remains controversial.MethodsWe used an animal model of radiation pneumonitis involving both radiation and simulated bacterial infection in Wistar rats. Treatment groups (10 rats/group) were as follows: control, RT-only, lipopolysaccharide (LPS)-only, and RT+LPS. All rats had micro-PET scans at 7 weeks after RT (or sham). Histologic, immunohistochemical, and biochemical analyses were performed to evaluate potential mechanisms.ResultsIrradiated rats had developed radiation pneumonitis at 7 weeks after RT based on pathology and CT scans. Maximum and mean standardized uptake values (SUVmax and SUVmean) at that time were significantly increased in the LPS group (P < 0.001 for both) and the RT+LPS group (P < 0.001 for both) relative to control, but were not different in the RT-only group (P = 0.156 SUVmax and P = 0.304 SUVmean). The combination of RT and LPS increased the expression of the aerobic glycolysis enzyme PKM2 (P < 0.001) and the glucose transporter GLUT1 (P = 0.004) in lung tissues. LPS alone increased the expression of PKM2 (P = 0.018), but RT alone did not affect PKM2 (P = 0.270) or GLUT1 (P = 0.989).ConclusionsAseptic radiation pneumonitis could not be accurately assessed by 18F-FDG PET, but was visualized after simulated bacterial infection via LPS. The underlying mechanism of the model of bacterial infection causing increased FDG uptake may be the Warburg effect.

Diagnostic Value of 18F-NOTA-FAPI PET/CT in a Rat Model of Radiation-Induced Lung Damage

“…Guo et al. concluded that 18 F-FDG imaging may not be able to diagnose aseptic radiation pneumonia in a murine model ( 34 ), whereas Abdulla et al. proposed that global lung parenchymal glycolysis and the mean standard uptake value in lung parenchyma may serve as useful biomarkers to quantify lung inflammation on FDG PET/CT following thoracic radiation therapy ( 35 ).…”

Diagnostic Value of 18 F-NOTA-FAPI PET/CT in A Rat Model of Radiation-induced Lung Damage

“…Several groups have investigated FDG-PET imaging as a method for assessing RIP. Guo et al concluded that 18F-FDG imaging may not be able to diagnose aseptic radiation pneumonia in a murine model [37], whereas Abdulla et al proposed that global lung parenchymal glycolysis and the mean standard uptake value in lung parenchyma may serve as useful biomarkers to quantify lung in ammation on FDG PET/CT following thoracic radiation therapy [38]. The imaging targets for the 18F-FDG and 18F-NOTA-FAPI tracers are different, with 18F-FDG revealing glucose metabolism imaging and 18F-NOTA-FAPI showing FAP expression.…”

Increased 18F-Fluoroestradiol Uptake of Radiation Pneumonitis in a Patient With Metastatic Breast Cancer

“…3 To date, no reliable and reproducible method for accurately detecting RP has been established. 4 The initial phase of RP typically shows ground-glass attenuation on CT image, aligning closely with the irradiated area. 5 In the clinic, some patients with RP manifest increases in FDG uptake, but others do not.…”

“…The initial phase of RP typically shows ground-glass attenuation on CT image, aligning closely with the irradiated area 5 . In the clinic, some patients with RP manifest increases in FDG uptake, but others do not 4 . The 18 F-FES is a PET tracer that targets ER, enabling in vivo imaging of ER-expressing tissues, mainly in breast cancer 6 .…”

“…The diagnosis of RP includes correlation between symptoms, imaging findings, and radiation history 3 . To date, no reliable and reproducible method for accurately detecting RP has been established 4 . The initial phase of RP typically shows ground-glass attenuation on CT image, aligning closely with the irradiated area 5 .…”