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

ABSTRACT: BACKGROUND:Radiation 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. METHODS:We 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. RESULTS:Irradiated 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). CONCLUSIONS:Aseptic 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.

SUBMITTER: Guo M

PROVIDER: S-EPMC6923299 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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<sup>18</sup>F-Fluorodeoxyglucose positron emission tomography may not visualize radiation pneumonitis.

Guo Meiying M Qi Liang L Zhang Yun Y Shang Dongping D Yu Jinming J Yue Jinbo J

EJNMMI research 20191219 1

<h4>Background</h4>Radiation 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 <sup>18</sup>F-FDG PET findings remains controversial.<h4>Methods</h4>We used an animal model of radiation pneumonitis involving both radiation and simulated bacterial infection in ...[more]

PMID: 31858307

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Project description:COPD and smoking are characterised by pulmonary inflammation. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) imaging may improve knowledge of pulmonary inflammation in COPD patients and aid early development of novel therapies as an imaging biomarker. To evaluate pulmonary inflammation, assessed by FDG uptake, in whole and regional lung in "usual" (smoking-related) COPD patients, alpha-1 antitrypsin deficiency (α1ATD) COPD patients, smokers without COPD and never-smokers using FDG PET/CT. Secondly, to explore cross-sectional associations between FDG PET/CT and systemic inflammatory markers in COPD patients and repeatability of the technique in COPD patients. Data from two imaging studies were evaluated. Pulmonary FDG uptake (normalised Ki; nKi) was measured by Patlak graphical analysis in four subject groups: 84 COPD patients, 11 α1ATD-COPD patients, 12 smokers and 10 never-smokers. Within the COPD group, associations between nKi and systemic markers of inflammation were assessed. Repeatability was evaluated in 32 COPD patients comparing nKi values at baseline and at 4-month follow-up. COPD patients, α1ATD-COPD patients and smokers had increased whole lung FDG uptake (nKi) compared with never-smokers (0.0037±0.001, 0.0040±0.001, 0.0040±0.001 versus 0.0028±0.001 mL·cm-3·min-1, respectively, p<0.05 for all). Similar results were observed in upper and middle lung regions. In COPD participants, plasma fibrinogen was associated with whole lung nKi (β=0.30, p=0.02) in multivariate analysis adjusted for current smoking, forced expiratory volume in 1 s % predicted, systemic neutrophils and C-reactive protein levels. Mean percentage difference in nKi between the baseline and follow-up was 3.2%, and the within subject coefficient of variability was 7.7%. FDG PET/CT has potential as a noninvasive tool to enable whole lung and regional quantification of FDG uptake to assess smoking- and COPD-related pulmonary inflammation.

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Project description:BackgroundPheochromocytomas and paragangliomas (PPGLs) are rare tumors of the adrenal medulla and extra-adrenal sympathetic chromaffin tissues; their anatomical and functional imaging are critical to guiding treatment decisions. This study aimed to compare the sensitivity and specificity of (18)F-fluorodeoxyglucose positron emission tomography with computed tomography ((18)F-FDG PET/CT) for tumor localization and staging of PPGLs with that of conventional imaging by [(123)I]-metaiodobenzylguanidine single photon emission CT ((123)I-MIBG SPECT), CT, and magnetic resonance imaging (MRI).MethodsA total of 216 patients (106 men, 110 women, aged 45.2 ± 14.9 years) with suspected PPGL underwent CT or MRI, (18)F-FDG PET/CT, and (123)I-MIBG SPECT/CT. Sensitivity and specificity were measured as endpoints and compared by the McNemar test, using two-sided P values only.ResultsSixty (28%) of patients had nonmetastatic PPGL, 95 (44%) had metastatic PPGL, and 61 (28%) were PPGL negative. For nonmetastatic tumors, the sensitivity of (18)F-FDG was similar to that of (123)I-MIBG but less than that of CT/MRI (sensitivity of (18)F-FDG = 76.8%; of (123)I-MIBG = 75.0%; of CT/MRI = 95.7%; (18)F-FDG vs (123)I-MIBG: difference = 1.8%, 95% confidence interval [CI] = -14.8% to 14.8%, P = .210; (18)F-FDG vs CT/MRI: difference = 18.9%, 95% CI = 9.4% to 28.3%, P < .001). The specificity was 90.2% for (18)F-FDG, 91.8% for (123)I-MIBG, and 90.2% for CT/MRI. (18)F-FDG uptake was higher in succinate dehydrogenase complex- and von Hippel-Lindau syndrome-related tumors than in multiple endocrine neoplasia type 2 (MEN2) related tumors. For metastases, sensitivity was greater for (18)F-FDG and CT/MRI than for (123)I-MIBG (sensitivity of (18)F-FDG = 82.5%; of (123)I-MIBG = 50.0%; of CT/MRI = 74.4%; (18)F-FDG vs (123)I-MIBG: difference = 32.5%, 95% CI = 22.3% to 42.5%, P < .001; CT/MRI vs (123)I-MIBG: difference = 24.4%, 95% CI = 11.3% to 31.6%, P < .001). For bone metastases, (18)F-FDG was more sensitive than CT/MRI (sensitivity of (18)F-FDG = 93.7%; of CT/MRI = 76.7%; difference = 17.0%, 95% CI = 4.9% to 28.5%, P = .013).ConclusionsCompared with (123)I-MIBG SPECT and CT/MRI, both considered gold standards for PPGL imaging, metastases were better detected by (18)F-FDG PET. (18)F-FDG PET provides a high specificity in patients with a biochemically established diagnosis of PPGL.

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

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<sup>18</sup>F-Fluorodeoxyglucose positron emission tomography may not visualize radiation pneumonitis.

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